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  • 1
    Electronic Resource
    Electronic Resource
    Anion channels of the inner membrane of mammalian and yeast mitochondria (1996)
    Springer
    Journal of bioenergetics and biomembranes 28 (1996), S. 125-130 
    Details
    ISSN: 1573-6881
    Keywords: Channel ; patch clamp ; mitochondria ; ClATP channels ; inner mitochondrial membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The inner membrane of yeast and mammalian mitochondria has been studiedin situ with a patch clamp electrode. Anion channels were found in both cases, although their behavior and regulation are different. In mammalian mitochondria, the principal channel is of around 100 pS conductance and opens mainly under depolarized membrane potentials. As no physiological compound able to alter its peculiar voltage dependence has yet been found, it is proposed that this channel may serve as a safeguard mechanism for recharging the mitochondrial membrane potential. Two other anion channels, each with a distinct conductance (one of approx. 45 pS, the second of at least a tenfold higher value) and kinetics are harbored in the yeast inner membrane. Matrix ATP was found to interact with both, but with a different mechanism. It is proposed that the 45 pS channel may be involved in the homeostatic mechanism of mitochondrial volume.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02110642
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  • 2
    Electronic Resource
    Electronic Resource
    Steady-State Proton Translocation in Bovine Heart Mitochondrial bc 1 Complex Reconstituted into Liposomes (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 81-87 
    Details
    ISSN: 1573-6881
    Keywords: bc 1 complex ; mitochondria ; cytochromes ; transmembrane pH difference ; H+/e − ratio ; decoupling ; azide ; arachidonate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The effect of different anions on the steady-state proton translocation in bovine bc 1 complex reconstituted in liposomes was studied. The H+/e − ratio for vectorial proton translocation is at the steady state definitely lower than that measured at level flow, (0.3 vs. 1.0). The presence of azide or arachidonate at micro- and submicromolar concentrations, respectively, gave a substantial reactivation of the proton pumping activity at the steady state, without any appreciable effect on respiration-dependent transmembrane pH difference. Addition of azide to turning-over bc 1 vesicles also caused a transition of b cytochromes toward oxidation. The results are discussed in terms of possible involvement of an acidic residue in the protonation of the semiquinone/quinol couple at the N side of the membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022467923837
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  • 3
    Electronic Resource
    Electronic Resource
    Nuclear Control of Respiratory Chain Expression in Mammalian Cells (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 109-119 
    Details
    ISSN: 1573-6881
    Keywords: ETS domain ; gene expression ; mammalian cells ; mitochondria ; nuclear respiratory factors ; oxidative phosphorylation ; regulation ; respiratory chain ; transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The majority of gene products required for mitochondrial respiratory function are encoded in the nuclear genome. These include most of the respiratory subunits and all of the proteins that regulate the mitochondrial genetic system. One approach to understanding nucleo-mitochondrial interactions in mammalian cells is to identify the nuclear transcription factors that are common to the expression of these gene products. This has led to the purification and molecular cloning of nuclear respiratory factors, NRF-1 and NRF-2. The DNA binding and transcriptional specificities of these proteins have implicated them in the expression of many respiratory subunits along with key components of the mitochondrial transcription, replication, and heme biosynthetic machinery. In addition, tissue-specific transcription factors have been linked to the coordinate synthesis of contractile proteins and muscle-specific respiratory subunits whereas other more ubiquitous factors may have a dual function in nuclear and mitochondrial gene activation. These findings provide a framework for further investigations of the nuclear genetic mechanisms that integrate the expression of the respiratory apparatus with that of other cellular systems during growth and development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022681828846
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  • 4
    Electronic Resource
    Electronic Resource
    Cardiolipin Remodeling in a Chinese Hamster Lung Fibroblast Cell Line Deficient in Oxidative Energy Production (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 291-298 
    Details
    ISSN: 1573-6881
    Keywords: Cardiolipin metabolism ; CCL16-B2 cells ; mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The metabolism of cardiolipin was investigated in a Chinese hamster lung fibroblast cell line CCL16-B2 deficient in oxidative energy metabolism and its parental cell line CCL16-B1. Mitochondrial enzyme activities involved in de novo cardiolipin biosynthesis were elevated in CCL16-B2 cells compared with CCL16-B1 cells, indicating initially an elevation in cardiolipin biosynthesis. Content of all phospholipids, including cardiolipin and its precursors, and high energy nucleotides were unaltered in CCL 16-B2 cells compared to CCL 16-B1 cells. When cells were incubated with [1,3-3H]glycerol for up to 4 h radioactivity incorporated into cardiolipin in CCL16-B2 cells did not differ compared with CCL16-B1 cells. In contrast, radioactivity incorporated into phosphatidylglycerol, the immediate precursor of cardiolipin, was elevated over 2-fold in CCL16-B2 cells compared with CCL16-B1 cells. Analysis of the fatty acid molecular species in cardiolipin revealed alterations in the level of unsaturated but not saturated fatty acids in B2 compared with B1 cells. In vivo cardiolipin remodeling, that is, the deacylation of cardiolipin to monolysocardiolipin followed by reacylation back to cardiolipin, with [1-14C]palmitate and [l-14C]oleate and in vitro mitochondrial phospholipid remodeling with [1-14C]linoleate were altered in CCL16-B2 cells compared to CCL16-B1 cells. Since both the appropriate content and molecular composition of cardiolipin is required for optimum mitochondrial oxidative phosphorylation, we suggest that the difference in CL molecular species composition observed in CCL16-B2 cells, mediated by alterations in in vivo cardiolipin remodeling, may be one of the underlying mechanisms for the reduction in oxidative energy production in CCL16-B2 cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022418328922
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  • 5
    Electronic Resource
    Electronic Resource
    On the Structure and Gating Mechanism of the Mitochondrial Channel, VDAC (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 525-531 
    Details
    ISSN: 1573-6881
    Keywords: Porin ; ion channel ; mitochondria ; VDAC ; electron microscopy ; sequence analysis ; β-barrel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract There is considerable evidence that the voltage-gated mitochondrial channel VDAC forms a β-barrel pore. Inferences about the number and tilt of β-strands can be drawn from comparisons with bacterial β-barrel pores whose structures have been determined by x-ray crystallography. A structural model for VDAC is proposed (based on sequence analysis and electron crystallography) in which the open state is like that of bacterial porins with several important differences. Because VDAC does not occur as close-packed trimers, there are probably fewer interpore contacts than in the bacterial porins. VDAC also appears to lack a large, fixed intraluminal segment and may not have as extensive a region of uniformly 35°-tilted β-strands as do the bacterial porins. These structural differences would be expected to render VDAC's β-barrel less stable than its bacterial counterparts, making major conformational changes like those associated with gating more energetically feasible. A possible gating mechanism is suggested in which movement of the N-terminal α-helix out of the lumen wall triggers larger-scale structural changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022489832594
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  • 6
    Electronic Resource
    Electronic Resource
    Localization at Complex I and Mechanism of the Higher Free Radical Production of Brain Nonsynaptic Mitochondria in the Short-Lived Rat Than in the Longevous Pigeon (1998)
    Springer
    Journal of bioenergetics and biomembranes 30 (1998), S. 235-243 
    Details
    ISSN: 1573-6881
    Keywords: Aging ; hydrogen peroxide ; mitochondria ; longevity ; bird
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Free radical production and leak of brain nonsynaptic mitochondria were higher with pyruvate/malate than with succinate in rats and pigeons. Rotenone, antimycin A, and myxothiazol maximally stimulated free radical production with pyruvate/malate but not with succinate. Simultaneous treatment with myxothiazol plus antimycin A did not decrease the stimulated rate of free radical production brought about independently by any of these two inhibitors with pyruvate/malate. Thenoyltrifluoroacetone did not increase free radical production with succinate. No free radical production was detected at Complex IV. Free radical production and leak with pyruvate/malate were higher in the rat (maximum longevity 4 years) than in the pigeon (maximum longevity 35 years). These differences between species disappeared in the presence of rotenone. The results localize the main free radical production site of nonsynaptic brain mitochondria at Complex I. They also suggest that the low free radical production of pigeon brain mitochondria is due to a low degree of reduction of Complex I in the steady state in this highly longevous species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020592719405
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetics of the Reconstituted Tricarboxylate Carrier from Eel Liver Mitochondria (1998)
    Springer
    Journal of bioenergetics and biomembranes 30 (1998), S. 555-563 
    Details
    ISSN: 1573-6881
    Keywords: Tricarboxylate carrier ; mitochondria ; transport ; liposomes ; kinetics ; reconstitution ; eel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The tricarboxylate carrier from eel liver mitochondria was purified by chromatography on hydroxyapatite and Matrix Gel Blue B and reconstituted into liposomes by removal of the detergent with Amberlite. Optimal transport activity was obtained by using a phospholipid concentration of 11.5 mg/ml, a Triton X-114/phospholipid ratio of 0.9, and ten passages through the same Amberlite column. The activity of the carrier was influenced by the phospholipid composition of the liposomes, being increased by cardiolipin and phosphatidylethanolamine and decreased by phosphatidylinositol. The reconstituted tricarboxylate carrier catalyzed a first-order reaction of citrate/citrate or citrate/malate exchange. The maximum transport rate of external [14C]citrate was 9.0 mmol/min per g of tricarboxylate carrier protein at 25°C and this value was virtually independent of the type of substrate present in the external or internal space of the liposomes. The half-saturation constant (K m) was 62 μM for citrate and 541 μM for malate. The activation energy of the citrate/citrate exchange reaction was 74 kJ/mol from 5 to 19°C and 31 kJ/mol from 19 to 35°C. The rate of the exchange had an external pH optimum of 8.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020532500749
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  • 8
    Electronic Resource
    Electronic Resource
    Reconstitution of the Mitochondrial ATP-Dependent Potassium Channel into Bilayer Lipid Membrane1 (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 159-163 
    Details
    ISSN: 1573-6881
    Keywords: KATP-channel ; solubilization ; mitochondria ; bilayer lipid membrane ; reconstruction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Electrical properties and regulation of the mitochondrialATP-dependent potassium channel were studied. The channel protein wassolubilized from the mitochondrial membrane using an ethanol/water mixture.Reconstituted into a bilayer lipid membrane BLM), the protein formed aslightly voltage-dependent channel with a conductance of 10 pS in 100 mM KCl.Often, several channels worked simultaneously (clusters) when many channelswere incorporated into the BLM. The elementary channel and the clusters wereboth highly potassium selective. At concentrations of 1 to 10 μM, ATPfavors channel opening, while channels become closed at 1–3 mM ATP. GDP(0.5 mM) reactivated the ATP-closed channels without affecting the untreatedchannels. The sulfhydryl-reducing agent ditiothreitol increased the openprobability at concentrations of 1 to 3 mM, but damaged the selectivity ofthe channel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005408029549
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  • 9
    Electronic Resource
    Electronic Resource
    A History of the First Uncoupling Protein, UCP1 (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 399-406 
    Details
    ISSN: 1573-6881
    Keywords: Brown adipose tissue ; mitochondria ; uncoupling protein ; UCP1 ; transport ; nucleotide ; fatty acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The lack of energy conservation in brown adipose tissue mitochondria when prepared byconventional methods was established in the 1960s and was correlated with the thermogenicfunction of the tissue. In order to observe energy conservation, two requirements had to bemet: the removal of the endogenous fatty acids and the addition of a purine nucleotide. Thesetwo factors have been the essential tools that led to the discovery of the energy dissipationpathway, the uncoupling protein UCP1. The activity is regulated by these two ligands. Purinenucleotides bind from the cytosolic side of the protein and inhibit transport. Fatty acids actas seconds messengers of noradrenaline and increase the proton conductance. This reviewpresents a historical perspective of the steps that led to the discovery of UCP1, its regulation,and our current view on its mechanism of transport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005436121005
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  • 10
    Electronic Resource
    Electronic Resource
    The Mechanisms of Fatty Acid-Induced Proton Permeability of the Inner Mitochondrial Membrane (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 447-455 
    Details
    ISSN: 1573-6881
    Keywords: Fatty acid ; uncoupling ; proton permeability ; adenine nucleotide translocase ; dicarboxylate carrier, glutamate/aspartate carrier ; permeability transition pore ; mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Nonesterified long-chain fatty acids have long been known as uncouplers of oxidativephosphorylation. They are efficient protonophores in the inner mitochondrial membrane but not so inartificial phospholipid membranes. In the un-ionized form, they undergo a rapid spontaneoustransbilayer movement (flip-flop). However, the transbilayer passage of the dissociated(anionic) form is hindered by the negatively charged hydrophilic carboxylic group. In theinner mitochondrial membrane, the transfer of fatty acid anions is mediated by the adeninenucleotide translocase, the dicarboxylate carrier, and the glutamate/aspartate carrier. As a result,the passage of protons and electric charges is a concerted effect of the spontaneous flip-flopof the undissociated (protonated) form in one direction and carrier-facilitated transfer of theionized (deprotonated) form in the other direction. In addition, fatty acids also promote openingof the mitochondrial permeability transition pore, presumably due to their interaction with oneof its constituents, the adenine nucleotide translocase, thus forming an additional route fordissipation of the proton gradient. Structural prerequisites for these proton-conductingmechanisms are (1) a weakly ionized carboxylic group and (2) a hydrocarbon chain of appropriatelength without substituents limiting its mobility and hydrophobicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005444322823
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  • 11
    Electronic Resource
    Electronic Resource
    Proton/electron stoichiometry of mitochondrialbc 1 complex. Influence of pH and transmembrane δpH (1995)
    Springer
    Journal of bioenergetics and biomembranes 27 (1995), S. 101-108 
    Details
    ISSN: 1573-6881
    Keywords: bc 1 complex ; mitochondria ; transmembrane pH difference ; cytochromes ; H +/e − stoichiometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The effect of pH and transmembrane δpH on the efficiency of the proton pump of the mitochondrialbc 1 complex bothin situ and in the reconstituted state was studied. In both cases the H+/e − ratio for vectorial proton translocation by thebc 1 complex respiring at the steady state, under conditions in which the transmembrane pH difference (δpH) represents the only component of the proton motive force (δp), was significantly lower than that measured under level flow conditions. The latter amounts, at neutral pH, to 1 (2 including the scalar H+ release). In the reconstituted system steady-state δpH was modulated by changing the intravesicular buffer as well as the intra/extra-liposomal pH. Under these conditions the H+/e− ratio varied inversely with the δpH. The data presented show that δpH exerts a critical control on the proton pump of thebc 1 complex. Increasing the external pH above neutrality caused a decrease of the level flowH +/e − ratio. This effect is explained in terms of proton/electron linkage inb cytochromes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02110337
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  • 12
    Electronic Resource
    Electronic Resource
    Glycine decarboxylase: Protein chemistry and molecular biology of the major protein in leaf mitochondria (1995)
    Springer
    Journal of bioenergetics and biomembranes 27 (1995), S. 407-414 
    Details
    ISSN: 1573-6881
    Keywords: Glycine decarboxylase ; mitochondria ; photorespiration ; gene expression ; light control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The four component proteins of the glycine decarboxylase multienzyme complex (the P-, H-, T-, and L-proteins) comprise over one-third of the soluble proteins in mitochondria isolated from the leaves of C3 plants. Together with serine hydroxymethyltransferase, glycine decarboxylase converts glycine to serine and is the site of photorespiratory CO2 and NH3 release. The component proteins of the complex are encoded on nuclear genes with N-terminal presequences that target them to the mitochondria. The isolated complex readily dissociates into its component proteins and reassociates into the intact complexin vitro. Because of the intimate association between photosynthesis and photorespiration, the proteins of the complex are present at higher levels in leaves in the light. The expression of these genes is controlled at the transcriptional level and the kinetics of expression are closely related to those of the small subunit of Rubisco. Deletion analysis of fusions between the promoter of the H-protein of the complex and the reporter gene β-glucuronidase in transgenic tobacco has identified a region responsible for the tissue specificity and light dependence of gene expression. Gel shift experiments show that a nuclear protein in leaves binds to this region. Glycine decarboxylase has proven to be an excellent system for studying problems in plant biochemistry ranging from protein-protein interactions to control of gene expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02110003
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  • 13
    Electronic Resource
    Electronic Resource
    URF13, a ligand-gated, pore-forming receptor for T-toxin in the inner membrane ofcms-T mitochondria (1995)
    Springer
    Journal of bioenergetics and biomembranes 27 (1995), S. 437-445 
    Details
    ISSN: 1573-6881
    Keywords: Maize ; mitochondria ; cytoplasmic male sterility ; URF13 ; T-urf13 ; T-toxin ; pathogenesis ; pore-forming receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract URF13 is the product of a mitochondrial-encoded gene (T-urfl3) found only in maize plants containing the Texas male-sterile cytoplasm (cms-T), and it is thought to be responsible for both cytoplasmic male sterility and the susceptibility ofcms-T maize to the fungal pathogensBipolaris maydis race T andPhyllosticta maydis. Mitochondria isolated fromcms-T maize are uniquely sensitive to pathotoxins (T-toxin) produced by these fungi and to methomyl (a commercial insecticide). URF13 acts as a receptor that specifically binds T-toxin to produce hydrophilic pores in the inner mitochondrial membrane. When expressed inEscherichia coli cells, URF13 also forms hydrophilic pores in the plasma membrane if exposed to T-toxin or methomyl. Topological studies established that URF13 contains three membrane-spanning α-helices, two of which are amphipathic and can contribute to pore formation. Chemical crosslinking of URF13 was used to demonstrate the existence of URF13 oligomers incms-T mitochondria andE. coli cells. The ability of the carboxylate-specific reagent,N,N∼-dicyclohexycarbodiimide, to cross-link URF13 was used in conjunction with site-directed mutagenesis to establish that the URF13 tetramer has a central core consisting of a four-α-helical bundle which undergoes a conformational change after interaction with T-toxin or methomyl. Overall, the experimental evidence indicates that URF13 functions as a ligand-gated, pore-forming T-toxin receptor incms-T mitochondria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02110006
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  • 14
    Electronic Resource
    Electronic Resource
    Structure-function relationships of the alternative oxidase of plant mitochondria: A model of the active site (1995)
    Springer
    Journal of bioenergetics and biomembranes 27 (1995), S. 367-377 
    Details
    ISSN: 1573-6881
    Keywords: Alternative oxidase ; sequence homology ; hydroxo-bridged di-iron center proteins ; mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract A major characteristic of plant mitochondria is the presence of a cyanide-insensitive alternative oxidase which catalyzes the reduction of oxygen to water. Current information on the properties of the oxidase is reviewed. Conserved amino acid motifs have been identified which suggest the presence of a hydroxo-bridged di-iron center in the active site of the alternative oxidase. On the basis of sequence comparison with other di-iron center proteins, a structural model for the active site of the alternative oxidase has been developed that has strong similarity to that of methane monoxygenase. Evidence is presented to suggest that the alternative oxidase of plant mitochondria is the newest member of the class II group of di-iron center proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02109999
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  • 15
    Electronic Resource
    Electronic Resource
    Functional molecular aspects of the NADH dehydrogenases of plant mitochondria (1995)
    Springer
    Journal of bioenergetics and biomembranes 27 (1995), S. 397-406 
    Details
    ISSN: 1573-6881
    Keywords: Plant ; respiration ; NADH dehydrogenases ; rotenone ; Complex I ; protein purification ; mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract There are multiple routes of NAD(P)H oxidation associated with the inner membrane of plant mitochondria. These are the phosphorylating NADH dehydrogenase, otherwise known as Complex I, and at least four other nonphosphorylating NAD(P)H dehydrogenases. Complex I has been isolated from beetroot, broad bean, and potato mitochondria. It has at least 32 polypeptides associated with it, contains FMN as its prosthetic group, and the purified enzyme is sensitive to inhibition by rotenone. In terms of subunit complexity it appears similar to the mammalian and fungal enzymes. Some polypeptides display antigenic similarity to subunits fromNeurospora crassa but little cross-reactivity to antisera raised against some beef heart complex I subunits. Plant complex I contains eight mitochondrial encoded subunits with the remainder being nuclear-encoded. Two of these mitochondrial-encoded subunits, nad7 and nad9, show homology to corresponding nuclear-encoded subunits inNeurospora crassa (49 and 30 kDa, respectively) and beef heart CI (49 and 31 kDa, respectively), suggesting a marked difference between the assembly of CI from plants and the fungal and mammalian enzymes. As well as complex I, plant mitochondria contain several type-II NAD(P)H dehydrogenases which mediate rotenone-insensitive oxidation of cytosolic and matrix NADH. We have isolated three of these dehydrogenases from beetroot mitochondria which are similar to enzymes isolated from potato mitochondria. Two of these enzymes are single polypeptides (32 and 55 kDa) and appear similar to those found in maize mitochondria, which have been localized to the outside of the inner membrane. The third enzyme appears to be a dimer comprised of two identical 43-kDa subunits. It is this enzyme that we believe contributes to rotenone-insensitive oxidation of matrix NADH. In addition to this type-II dehydrogenases, several observations suggest the presence of a smaller form of CI present in plant mitochondria which is insensitive to rotenone inhibition. We propose that this represents the peripheral arm of CI in plant mitochondria and may participate in nonphosphorylating matrix NADH oxidation.
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    URL: http://dx.doi.org/10.1007/BF02110002
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  • 16
    Electronic Resource
    Electronic Resource
    Hypothyroidism Leads to a Decreased Expression of Mitochondrial F0F1-ATP Synthase in Rat Liver (1998)
    Springer
    Journal of bioenergetics and biomembranes 30 (1998), S. 269-276 
    Details
    ISSN: 1573-6881
    Keywords: Hypothyroidism ; oxidative phophorylation ; mitochondria ; F0F1-ATP synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract In liver mitochondria isolated from hypothyroid rats, the rate of ATP synthesis is lower than in mitochondria from normal rats. Oligomycin-sensitive ATP hydrolase activity and passive proton permeability were significantly lower in submitochondrial particles from hypothyroid rats compared to those isolated from normal rats. In mitochondria from hypothyroid rats, the changes in catalytic activities of F0F1-ATP synthase are accompanied by a decrease in the amount of immunodetected β-F1, F01-PVP, and OSCP subunits of the complex. Northern blot hybridization shows a decrease in the relative cytosolic content of mRNA for β-F1 subunit in liver of hypothyroid rats. Administration of 3,5,3′-triodo-L-thyronine to the hypothyroid rats tends to remedy the functional and structural defects of F0F1-ATP synthase observed in the hypothyroid rats. The results obtained indicate that hypothyroidism leads to a decreased expression of F0F1-ATP synthase complex in liver mitochondria and this contributes to the decrease of the efficiency of oxidative phosphorylation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020548904384
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  • 17
    Electronic Resource
    Electronic Resource
    Mitochondrial Redox Signaling during Apoptosis (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 327-334 
    Details
    ISSN: 1573-6881
    Keywords: Apoptosis ; redox ; mitochondria ; E h ; ROS ; ASK-1 ; thioredoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The regulatory role of cellular redox state during apoptosis is still controversial. Early redoxsignaling can transduce divergent upstream signals to mitochondria and initiate apoptosis. Onthe other hand, release of mitochondrial cytochrome c triggers generation of reactive oxygenspecies (ROS) and renders apoptotic cells much more oxidized. Although the sequential caspaseactivation does not have apparent redox-sensitive components, redox signaling provides aseparate pathway that is parallel with the caspase cascade. The function of theapoptosis-associated redox change is uncertain. It could provide positive feedback mechanisms, such asactivating mitochondrial permeability transition and apoptosis signaling kinase (ASK-1). Sinceapoptotic cells are designated to be quickly eliminated, the dramatic cellular oxidation couldbe involved in the final degradation of apoptotic bodies and even the termination of theproteolytic activity after phagocytosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005423818280
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  • 18
    Electronic Resource
    Electronic Resource
    Mitochondrial Oxygen Radical Generation and Leak: Sites of Production in States 4 and 3, Organ Specificity, and Relation to Aging and Longevity (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 347-366 
    Details
    ISSN: 1573-6881
    Keywords: Free radicals ; H2O2 ; complex I ; heart ; brain ; free-radical leak ; complex III ; mitochondria ; aging ; longevity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Studies in heart and nonsynaptic brain mitochondria from two mammals and three birds showthat complex I generates oxygen radicals in heart and nonsynaptic brain mitochondria in States4 and 3, whereas complex III does it only in heart mitochondria and only in State 4. Theincrease in oxygen consumption during the State 4 to 3 transition is not accompanied by aproportional increase in oxygen radical generation. This will protect mitochondria and tissuesduring bursts of activity. Comparisons between young and old rodents do not show a consistentpattern of variation in mitochondrial oxygen radical production during aging. However, allthe interspecies comparisons performed to date between different mammals, and betweenmammals and birds, agree that animals with high maximum longevities have low rates ofmitochondrial oxygen radical production, irrespective of the value of their basal specificmetabolic rate. The sites and mechanisms allowing this, the recently described low degree ofmembrane fatty acid unsaturation of longevous animals, and their relation to longevity andaging are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005427919188
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  • 19
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    Anion Carriers in Fatty Acid-Mediated Physiological Uncoupling (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 431-445 
    Details
    ISSN: 1573-6881
    Keywords: Uncoupling ; thermoregulation ; mitochondria ; ATP/ADP antiporter ; aspartate/glutamate antiporter ; uncoupling proteins 1, 2, 3 ; plant uncoupling protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Physiological aspects of uncoupling of oxidation and phosphorylation are reviewed in thecontext of involvement of mitochondrial anion carriers. It is assumed that the carriers facilitateelectrophoretic translation of fatty acid anion, RCOO-, from the inner to the outer leaflet ofthe mitochondrial membrane, whereas back movement of the protonated fatty acid, RCOOH,from the outer to the inner leaflet represents flip-flop of RCOOH via the phospholipid bilayerof the membrane. The RCOO- transport seems to be catalyzed by the ATP/ADP and aspartate/glutamate antiporters, dicarboxylate carrier, and uncoupling proteins (UCP1, UCP2, UCP3L,UCP3s, and plant UCP). The fatty acid uncoupling is shown to be involved in thethermoregulatory heat production in animals and plants exposed to cold, as well as in performance ofrespiratory functions other than ATP synthesis, i.e., formation of useful substances,decomposition of unwanted substances, and antioxidant defense. Moreover, partial uncoupling might takepart in optimization of the rate of ATP synthesis in aerobic cells.
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    URL: http://dx.doi.org/10.1023/A:1005492205984
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    Mitochondrial Proton Leak and the Uncoupling Proteins (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 517-524 
    Details
    ISSN: 1573-6881
    Keywords: Proton leak ; uncoupling proteins ; UCP1 ; UCP2 ; UCP3 ; BMCP1 ; thermogenesis ; sequence homology ; mitochondria ; respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract An energetically significant leak of protons occurs across the mitochondrial inner membranesof eukaryotic cells. This seemingly wasteful proton leak accounts for at least 20% of thestandard metabolic rate of a rat. There is evidence that it makes a similar contribution tostandard metabolic rate in a lizard. Proton conductance of the mitochondrial inner membranecan be considered as having two components: a basal component present in all mitochondria,and an augmentative component, which may occur in tissues of mammals and perhaps ofsome other animals. The uncoupling protein of brown adipose tissue, UCP1, is a clear exampleof such an augmentative component. The newly discovered UCP1 homologs, UCP2, UCP3,and brain mitochondrial carrier protein 1 (BMCP1) may participate in the augmentativecomponent of proton leak. However, they do not appear to catalyze the basal leak, as this isobserved in mitochondria from cells which apparently lack these proteins. Whereas UCP1plays an important role in thermogenesis, the evidence that UCP2 and UCP3 do likewiseremains equivocal.
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    URL: http://dx.doi.org/10.1023/A:1005456725549
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    Inactivation of the Reconstituted Oxoglutarate Carrier from Bovine Heart Mitochondria by Pyridoxal 5′-Phosphate (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 535-541 
    Details
    ISSN: 1573-6881
    Keywords: Oxoglutarate carrier ; pyridoxal 5′-phosphate ; transport ; proteoliposomes ; mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The effect of pyridoxal 5′-phosphate and some other lysine reagents on the purified,reconstituted mitochondrial oxoglutarate transport protein has been investigated. The inhibition ofoxoglutarate/oxoglutarate exchange by pyridoxal 5′-phosphate can be reversed by passing theproteoliposomes through a Sephadex column but the reduction of the Schiff's base by sodiumborohydride yielded an irreversible inactivation of the oxoglutarate carrier protein. Pyridoxal5′-phosphate, which caused a time- and concentration-dependent inactivation of oxoglutaratetransport with an IC50 of 0.5 mM, competed with the substrate for binding to the oxoglutaratecarrier (K i = 0.4 mM). Kinetic analysis of oxoglutarate transport inhibition by pyridoxal5′-phosphate indicated that modification of a single amino acid residue/carrier molecule wassufficient for complete inhibition of oxoglutarate transport. After reduction with sodiumborohydride [3H]pyridoxal 5′-phosphate bound covalently to the oxoglutarate carrier. Incubation ofthe proteoliposomes with oxoglutarate or L-malate protected the carrier against inactivationand no radioactivity was found associated with the carrier protein. In contrast, glutarate andsubstrates of other mitochondrial carrier proteins were unable to protect the carrier. Mersalyl,which is a known sulfhydryl reagent, also failed to protect the oxoglutarate carrier againstinhibition by pyridoxal 5′-phosphate. These results indicate that pyridoxal 5′-phosphateinteracts with the oxoglutarate carrier at a site(s) (i.e., a lysine residue(s) and/or the amino-terminalglycine residue) which is essential for substrate translocation and may be localized at or nearthe substrate-binding site.
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    URL: http://dx.doi.org/10.1023/A:1026414826457
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    5-Aminolevulinate synthase and the first step of heme biosynthesis (1995)
    Springer
    Journal of bioenergetics and biomembranes 27 (1995), S. 151-159 
    Details
    ISSN: 1573-6881
    Keywords: Heme ; 5-aminolevulinate ; pyridoxal 5′-phosphate ; mitochondria ; heme metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract 5-Aminolevulinate synthase catalyzes the condensation of glycine and succinyl-CoA to yield 5-aminolevulinate. In animals, fungi, and some bacteria, 5-aminolevulinate synthase is the first enzyme of the heme biosynthetic pathway. Mutations on the human erythroid 5-aminolevulinate synthase, which is localized on the X-chromosome, have been associated with X-linked sideroblastic anemia. Recent biochemical and molecular biological developments provide important insights into the structure and function of this enzyme. In animals, two aminolevulinate synthase genes, one housekeeping and one erythroid-specific, have been identified. In addition, the isolation of 5-aminolevulinate synthase genomic and cDNA clones have permitted the development of expression systems, which have tremendously increased the yields of purified enzyme, facilitating structural and functional studies. A lysine residue has been identified as the residue involved in the Schiff base linkage of the pyridoxal 5′-phosphate cofactor, and the catalytic domain has been assigned to the C-terminus of the enzyme. A conserved glycine-rich motif, common to all aminolevulinate synthases, has been proposed to be at the pyridoxal 5′phosphate-binding site. A heme-regulatory motif, present in the presequences of 5-aminolevulinate synthase precursors, has been shown to mediate the inhibition of the mitochondrial import of the precursor proteins in the presence of heme. Finally, the regulatory mechanisms, exerted by an iron-responsive element binding protein, during the translation of erythroid 5-aminolevulinate synthase mRNA, are discussed in relation to heme biosynthesis.
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    URL: http://dx.doi.org/10.1007/BF02110030
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    The First Steps of Protein Import into Mitochondria (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 11-17 
    Details
    ISSN: 1573-6881
    Keywords: Protein targeting ; protein import ; mitochondria ; molecular chaperones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Protein import into mitochondria is initiated by the recognition and binding of precursor proteins by import components in the cytosol, on the mitochondrial surface, and in the mitochondrial outer membrane. Following their synthesis on cytoplasmic ribosomes, some precursor proteins interact with molecular chaperones in the cytosol which function in maintaining the precursor protein in an import-competent state and may also aid in the delivery of the precursor to the mitochondria. A multisubunit protein import receptor then recognises and binds precursor proteins before feeding them into the outer membrane import site. Some proteins are sorted from the import site into the outer membrane, but most precursor proteins travel through the outer membrane import site into the mitochondria, where the later steps of protein import take place.
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    URL: http://dx.doi.org/10.1023/A:1022451520203
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    Molecular Chaperones and Mitochondrial Protein Folding (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 35-43 
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    ISSN: 1573-6881
    Keywords: Chaperonins ; heat-shock proteins ; mitochondria ; molecular chaperones ; protein folding ; protein import
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Precursor proteins destined for the mitochondrial matrix traverse inner and outer organelle membranes in an extended conformation. Translocation events are therefore integrally coupled to the processes of protein unfolding in the cytosol and protein refolding in the matrix. To successfully import proteins from the cytoplasm into mitochondria, cells have recruited a variety of molecular chaperone systems and folding catalysts. Within the organelles, mitochondrial Hsp70 (mt-Hsp70) is a major player in this process and exerts multiple functions. First, mt-Hsp70 binds together with cohort proteins to incoming polypeptide chains, thus conferring unidirectionality on the translocation process, and then assists in their refolding. A subset of imported proteins requires additional assistance by chaperonins of the Hsp60/Hsp10 family. Protein folding occurs within the cavity of these cylindrical complexes. A productive interaction of precursor proteins with molecular chaperones in the matrix is not only crucial for correct refolding and assembly, but also for processing of presequences, intramitochondrial sorting, and degradation of proteins. This review focuses on the role of mt-Hsp70 and Hsp60/Hsp10 in protein folding in the mitochondrial matrix and discusses recent findings on their molecular mechanism of action.
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    URL: http://dx.doi.org/10.1023/A:1022407705182
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    Proton Pumping of Mitochondrial Complex I: Differential Activation by Analogs of Ubiquinone (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 71-80 
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    ISSN: 1573-6881
    Keywords: NADH: ubiquinone reductase ; ubiquinone ; proton pumping ; mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract As part of the ongoing studies aimed at elucidating the mechanism of the energy conserving function of mitochondrial complex I, NADH: ubiquinone (Q) reductase, we have investigated how short-chain Q analogs activate the proton pumping function of this complex. Using a pH-sensitive fluorescent dye we have monitored both the extent and initial velocity of proton pumping of complex I in submitochondrial particles. The results are consistent with two sites of interaction of Q analogs with complex I, each having different proton pumping capacity. One is the physiological site which leads to a rapid proton pumping and a stoichiometric consumption of NADH associated with the reduction of the most hydrophobic Q analogs. Of these, heptyl-Q appears to be the most efficient substrate in the assay of proton pumping. Q analogs with a short-chain of less than six carbons interact with a second site which drives a slow proton pumping activity associated with NADH oxidation that is overstoichiometric to the reduced quinone acceptor. This activity is also nonphysiological, since hydrophilic Q analogs show little or no respiratory control ratio of their NADH:Q reductase activity, contrary to hydrophobic Q analogs.
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    Homologous and Heterologous Interactions between Hexokinase and Mitochondrial Porin: Evolutionary Implications (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 97-102 
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    ISSN: 1573-6881
    Keywords: Hexokinase ; binding to mitochondria ; mitochondria ; binding of hexokinase to ; Porin ; VDAC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Binding of the Type I isozyme of mammalian hexokinase to mitochondria is mediated by the porin present in the outer mitochondrial membrane. Type I hexokinase from rat brain is avidly bound by rat liver mitochondria while, under the same conditions, there is no significant binding to mitochondria from S. cerevisiae. Previously published work demonstrates the lack of significant interaction of yeast hexokinase with mitochondria from either liver or yeast. Thus, structural features required for the interaction of porin and hexokinase must have emerged during evolution of the mammalian forms of these proteins. If these structural features serve no functional role other than facilitating this interaction of hexokinase with mitochondria, it seems likely that they evolved in synchrony since operation of selective pressures on the hexokinase–mitochondrial interaction would require the simultaneous presence of hexokinase and porin capable of at least minimal interaction, and be responsive to changes in either partner that affected this interaction. Recent studies have indicated that a second type of binding site, which may or may not involve porin, is present on mammalian mitochondria. There are also reports of hexokinase binding to mitochondria in plant tissues, but the nature of the binding site remains undefined.
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    ADP-Regulation of Mitochondrial Free Radical Production Is Different with Complex I- or Complex II-Linked Substrates: Implications for the Exercise Paradox and Brain Hypermetabolism (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 241-249 
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    ISSN: 1573-6881
    Keywords: ADP ; mitochondria ; free radical production ; brain ; heart ; exercise ; hypermetabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract In agreement with classic studies, succinate-supplemented rat and pigeon heart and nonsynaptic brain mitochondrial free radical production is stopped by ADP additions causing the stimulation of respiration from State 4 to State 3. Nevertheless, with Complex I-linked substrates, mitochondria produce free radicals in State 3 at rates similar or somewhat higher than during resting respiration. The absence of sharp increases in free radical production during intense respiration is possible due to strong decreases of free radical leak in State 3. The results indicate that Complex I is the main mitochondrial free radical generator in State 3, adding to its already known important generation of active oxygen species in State 4. The observed rate of mitochondrial free radical production with Complex I-linked substrates in the active State 3 can help to explain two paradoxes: (a) the lack of massive muscle oxidative damage and shortening of life span due to exercise, in spite of up to 23-fold increases of oxygen consumption together with the very low levels of antioxidants present in heart, skeletal muscle, and brain; (b) the presence of some degree of oxidative stress during exercise and hyperactivity in spite of the stop of mitochondrial free radical production by ADP with succinate as substrate.
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    Localized Firefly Luciferase Probes ATP at the Surface of Mitochondria (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 549-559 
    Details
    ISSN: 1573-6881
    Keywords: Luciferase ; localized probe ; heterogeneous coupled systems ; mitochondria ; hexokinase ; nucleotide concentration gradients ; cellular catalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The concentration of ATP generated by yeast mitochondria and consumed by yeast hexokinase was monitored using native firefly luciferase in solution, or recombinant luciferase localized at the surface of mitochondria. In the absence of hexokinase, both probes perform similarly in detecting exogenous or mitochondrially-generated ATP. The steady-state concentrations of ATP can be reduced in a dose-dependent manner by hexokinase. With hexokinase added in large excess, the localized probe reports substantial ATP concentrations while none is detectable by soluble luciferase. Thus, ATP accumulates near the membrane where it appears, relatively to solution, and vice versa for ADP. The extent of nucleotide gradients is shown to be correlated with the specific activity of oxidative phosphorylation and with the viscosity of the medium, but independent of the concentration of the organelles. A simple model involving diffusional restrictions is presented to describe this behavior. The metabolic and evolutionary implications of cellular catalysis limitation by physical processes are discussed.
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    Mitochondrial Ca2+ Transients in Cardiac Myocytes During the Excitation–Contraction Cycle: Effects of Pacing and Hormonal Stimulation (1998)
    Springer
    Journal of bioenergetics and biomembranes 30 (1998), S. 207-222 
    Details
    ISSN: 1573-6881
    Keywords: Calcium ; cardiac myocytes ; confocal microscopy ; Fluo 3 ; Indo 1 ; isoproterenol ; mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Using laser scanning confocal microscopy, our objective was to measure mitochondrial, nuclear, and cytosolic free ionized Ca2+ in adult rabbit cardiac myocytes loaded with Ca2+-indicating fluorophores. When myocytes were loaded with Fluo 3 at 37°C, the fluorophore was loaded extensively into the cytosol and nucleus, but poorly into mitochondria, and Fluo 3 fluorescence transients after field stimulation were confined to the cytosol and nucleus. In contrast, after loading at 4°C, Fluo 3 also entered mitochondria, and large transients of mitochondrial Fluo 3 fluorescence then occurred after stimulation. Isoproterenol (1 μM) increased the magnitude of Ca2+ transients and their subsequent rate of decay, an effect more marked in the cytosol and nucleus than in mitochondria. As pacing frequency was increased from 0.5 to 2 Hz, diastolic mitochondrial Ca2+ rose markedly in the absence but not in the presence of isoproterenol. Resting Ca2+ estimated by Indo 1 ratio imaging using UV/visible laser scanning confocal microscopy was about 200 nM in all compartments. During field stimulation, Ca2+ transiently increased to 671, 522, and 487 nM in cytosol, interfibrillar mitochondria, and perinuclear mitochondria, respectively. Isoproterenol increased these respective peak values to 1280, 750, and 573 nM. These results were consistent with those obtained in Fluo 3 experiments. We conclude that rapid mitochondrial Ca2+ transients occur during excitation–contraction coupling in adult rabbit cardiac myocytes, which may be important in matching mitochondrial metabolism to myocardial ATP demand during changes in cardiac output.
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    Electron Tomography of Mitochondria from Brown Adipocytes Reveals Crista Junctions (1998)
    Springer
    Journal of bioenergetics and biomembranes 30 (1998), S. 431-442 
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    ISSN: 1573-6881
    Keywords: BAT mitochondria ; brown adipocytes ; contact sites ; crista junctions ; cristae ; cristae structure ; electron microscopy ; electron microscope tomography ; mitochondria ; mitochondrial structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Electron microscope tomography was used to examine the membrane topology of brown adipose tissue (BAT) mitochondria prepared by cryofixation or chemical fixation techniques. These mitochondria contain an uncoupling protein which results in the conversion of energy from electron transport into heat. The three-dimensional reconstructions of BAT mitochondria provided a view of the inner mitochondrial membrane different in important features from descriptions found in the literature. The work reported here provides new insight into BAT mitochondria architecture by identifying crista junctions, including multiple junctions connecting a crista to the same side of the inner boundary membrane, in a class of mitochondria that have no tubular cristae, but only lamellar cristae. Crista junctions were defined previously as the tubular membranes of relatively uniform diameter that connect a crista membrane with the inner boundary membrane. We have also found that the cristae architecture of cryofixed mitochondria, including crista junctions, is similar to that found in chemically fixed mitochondria, suggesting that this architecture is not a fixation artifact. The stacks of lamellar cristae extended through more of the BAT mitochondrial volume than did the cristae we observed in neuronal mitochondria. Hence, the inner membrane surface area was larger in the former. In chemically fixed mitochondria, contact sites were easily visualized because the outer and inner boundary membranes were separated by an 8 nm space. However, in cryofixed mitochondria almost all the outer membrane was observed to be in close contact with the inner boundary membrane.
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    Subunit f of the Yeast Mitochondrial ATP Synthase: Topological and Functional Studies (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 85-94 
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    ISSN: 1573-6881
    Keywords: yeast ; mitochondria ; ATP synthase ; ATP17 gene ; subunit f ; orientation ; cross-linking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Modified versions of subunit f were produced by mutagenesis of theATP17 gene of Saccharomyces cerevisiae. A version of subunit f devoid of thelast 28 amino acid residues including the unique transmembranous domaincomplemented the oxidative phosphorylation of the null mutant. However, atwo-fold decrease in the specific ATP synthase activity was measured andattributed to a decrease in the stability of the mutant ATP synthase complexas shown by the low oligomycin-sensitive ATPase activity at alkaline pH. Themodification or not by non-permeant maleimide reagents of cysteine residuesintroduced at the N and C termini of subunit f indicated aNin-Cout orientation. From the C terminus of subunit fit was possible to cross-link subunit 4 (also called subunit b), which isanother component of the F0 sector and which also displays a shorthydrophilic segment exposed to the intermembrane space.
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    The Role of the Amino-Terminal β-Barrel Domain of the α and β Subunits in the Yeast F1-ATPase (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 95-104 
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    ISSN: 1573-6881
    Keywords: F1-ATPase ; β-barrel domain ; mitochondria ; assembly ; yeast ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The crystal structure of mitochondrial F1-ATPase indicatesthat the α and β subunits fold into a structure defined by threedomains: the top β-barrel domain, the middle nucleotide-binding domain,and the C-terminal α-helix bundle domain (Abraham et al.1994); Bianchet et al., 1998). The β-barrel domains of theα and β subunits form a crown structure at the top ofF1, which was suggested to stabilize it (Abraham et al.1994). In this study. the role of the β-barrel domain in the α andβ subunits of the yeast Saccharomyces cerevisiae F1,with regard to its folding and assembly, was investigated. The β-barreldomains of yeast F1 α and β subunits were expressedindividually and together in Escherichia coli. When expressedseperately, the β-barrel domain of the β subunit formed a largeaggregate structure, while the domain of the α subunit waspredominately a monomer or dimer. However, coexpression of the β-barreldomain of α subunit domain. Furthermore, the two domains copurified incomplexes with the major portion of the complex found in a small molecularweight form. These results indicate that the β-barrel domain of theα and β subunits interact specifically with each other and thatthese interactions prevent the aggregation of the β-barrel domain of theβ subunit. These results mimic in vivo results and suggest thatthe interactions of the β-barrel domains may be critical during thefolding and assembly of F1.
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    On the Role of the General Transcription Factor Sp1 in the Activation and Repression of Diverse Mammalian Oxidative Phosphorylation Genes* (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 129-135 
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    ISSN: 1573-6881
    Keywords: mitochondria ; promoter ; transcription regulation ; Sp1 ; repressor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract To gain insight into the role of the general transcription factor,Sp1, in the expression of nuclear genes involved in mitochondrial biogenesis,we investigated Sp1 activation of the adenine nucleotide translocator 2,cytochrome c1, F1-ATPase β subunit, and themitochondria transcription factor (mtTFA) promoters transfected intoDrosophila cell lines. The numbers and organization of GC elementsvary in the four promoters, but the magnitude of activation by coexpressedhuman Sp1 was similar. A feature common to the four promoters is the presenceof multiple, proximal Sp1-activating elements that account for 50% ormore of the transcription activation by Sp1. The distribution and function ofindividual distal Sp1 elements is less defined and appear to be morepromoter-specific. Finally, data from transfected Drosophila cellsprovide the first direct proof for the involvement of Sp1 in the negativeregulation of the ANT2 promoter and as a possible participant in repressionof the β-subunit promoter. The role of Sp1 in both the positive andnegative regulation of OXPHOS promoters is unique.
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    Activation and Deactivation of F0F1-ATPase in Yeast Mitochrondia (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 105-117 
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    ISSN: 1573-6881
    Keywords: mitochondria ; F0F1 ATPase ; ATP synthase ; ATP hydrolysis ; IF1 ; yeast ; regulation ; inactivation ; proton gradient ; detergent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The regulation of membrane-bound proton F0F1ATPase by the protonmotive force and nucleotides was studied in yeastmitochondria. Activation occurred in whole mitochondria and the ATPaseactivity was measured just after disrupting the membranes with Triton X-100.Deactivation occurred either in whole mitochondria uncoupled with FCCP, or indisrupted membranes. No effect of Triton X-100 on the ATPase was observed,except a slow reactivation observed only in the absence of MgADP. BothAMPPNP and ATP increased the ATPase deactivation rate, thus indicating thatoccupancy of nucleotidic sites by ATP is more decisive than catalyticturnover for this process. ADP was found to stimulate the energy-dependentATPase activation. ATPase deactivated at the same rate in uncoupled anddisrupted mitochondria. This suggests that deactivation is not controlled byrebinding of some soluble factor, like IF1, but rather by the conversion ofthe F1.IF1 complex into an inactive form.
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    Mutation of K234 and K236 in the Voltage-Dependent Anion Channel 1 Impairs Its Insertion into the Mitochondrial Outer Membrane (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 137-142 
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    ISSN: 1573-6881
    Keywords: VDAC1 ; mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Previous in vitro studies indicated that mutation of bothK234 and K236 to arginine, glutamine, or glutamic acid impaired the abilityof the voltage-dependent anion channel (VDAC1) to insert into the outermembrane of the mitochondria (Smith et al. 1995). These same mutantswere expressed in a strain of Saccharomyces cerevisiae with adisruption in the VDAC1 gene. The mutant VDAC1 forms were found in themitochondria suggesting that they were correctly sorted to the outermembrane. However, only very small amounts of the mutants were inserted intothe mitochondrial membranes. Mitochondria isolated from the strains expressingthe mutants were capable of catalyzing the translocation of both wild-typeVDAC1 and pre-alcohol dehydrogenase III indicating that the translocationapparatus was functional. These results confirm the previously drawnconclusion that K234 and K236 are part of a membrane insertion motif. Thefailure of the mutant VDAC1 forms to insert did not cause VDAC1 precursors toaccumulate in the soluble cell cytoplasm or in the microsomal fraction. Theapparent lack of a “precursor pool” suggested that apost-transcriptional control mechanism might limit the amounts of VDAC1precursors in the cell. Such a control mechanism is consistent with theobservation that the amount of VDAC1 was very similar after epichromosomal(gene in a 2u plasmid controlled by a Gal1 promoter) and chromosomalexpression (endogenous gene controlled by the endogenous promoter).
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    Mutations in the Voltage-Dependent Anion Channel of the Mitochondrial Outer Membrane Cause a Dominant Nonlethal Growth Impairment (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 143-151 
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    ISSN: 1573-6881
    Keywords: VDAC1 ; mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Point mutations at K234 and K236 in the yeast voltage-dependent anionchannel 1 (VDAC1) of the mitochondrial outer membrane have been shown tomarkedly impair the membrane insertion of this protein (Smith etal., 1995; Angeles et al., 1998). Mutants of this type wereexpressed in vivo in a strain of yeast with a disruption in theVDAC1 gene. Expression of the various VDAC1 forms was under the control of aGal1 promoter. Wild-type VDAC1 expression fully complemented the slow growthphenotype caused by the disruption. VDAC1 mutants in which K234 and K236 werereplaced by arginine, glutamate, or glutamine caused a more severe negativeeffect on growth. This effect appeared to be dominant since the mutant VDAC1forms suppressed growth in a yeast strain that retained its VDAC1 gene. Thisapparent dominant negative effect on growth did not seem to be specific forany stage of the cell cycle. However, the growth defect was not lethal as theaffected cells still could accumulate the vital stain, FUN1. Expression of amutant in which K234 had been replaced by glutamate had more serious negativegrowth effects than did a similar mutation at K236. Expression ofΔ71-116 VDAC1 complemented the VDAC1 disruption; however, expression ofthe same deletion mutant in which the lysines corresponding to K234 and K236were mutated to glutamate severely impaired growth. These results have shownthat a deficiency of lysine at positions 234 and 236 in VDAC1 causes anonlethal growth defect that is more severe than deletion of 45 amino acidsfrom VDAC1 or disruption of the VDAC1 gene. They also indicate that there is ahierarchy in the importance of these lysines with mutations at K234 being themore serious.
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    URL: http://dx.doi.org/10.1023/A:1005403928641
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    Mitochondrial Events in the Life and Death of Animal Cells: A Brief Overview (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 291-304 
    Details
    ISSN: 1573-6881
    Keywords: Cell death ; aging ; necrosis ; apoptosis ; mitochondria ; oxidative phosphorylation ; electron transport chain ; ATP synthase ; cytochrome c ; mitochondrial DNA ; reactive oxygen species (ROS)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Traditionally, mitochondria have been viewed as the “powerhouse” of the cell, i.e., the site of theoxidative phosphorylation machinery involved in ATP production. Consequently, much of theresearch conducted on mitochondria over the past 4 decades has focused on elucidating both thosemolecular events involved in ATP synthesis by oxidative phosphorylation and those involved inthe biogenesis of the oxidative phosphorylation machinery. While monumental achievements havebeen made, and continue to be made, in the study of these remarkable but extremely complexprocesses essential for the life of most animal cells, it has been only in recent years that a largebody of biological and biomedical scientists have come to recognize that mitochondria participatein other important processes. Two of these are cell death and aging which, not surprisingly, are relatedprocesses both involving, in part, the oxidative phosphorylation machinery. This new awareness hassparked a new and growing area of mitochondrial research, that has become of great interest to awide variety of scientists ranging from those involved in elucidating the role of mitochondria incell death and aging to those interested in either suppressing or facilitating these processes as itrelates to identifying new therapies or drugs for human disease. It is the purpose of this briefintroductory review to provide an overview of those mitochondrial events involved in the life anddeath of animal cells and to indicate how these events might relate to the human aging process.Much more is known, much remains controversial, and even more remains to be learned as indicatedin the excellent set of minireviews that follow.
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    URL: http://dx.doi.org/10.1023/A:1005453700533
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    Inhibitory Properties of Ruthenium Amine Complexes on Mitochondrial Calcium Uptake (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 551-557 
    Details
    ISSN: 1573-6881
    Keywords: Calcium uniporter inhibitors ; mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The recent finding that the inhibition of Ca2+-stimulated respiration by ruthenium red is mainlydue to a binuclear ruthenium complex (Ru360) present in the commercial samples of the classicalinhibitor ruthenium red (Ying et. al., 1991), showed that this complex is the more potent andspecific inhibitor of the mitochondrial calcium uniporter. This work was aimed to provideinsights into the mechanism by which Ru360 and other ruthenium-related compounds inhibitscalcium uptake. Ruthenium red and a synthesized analog (Rrphen) were compared with Ru360.The inhibition by this binuclear complex was noncompetitive, with a K i of 9.89 nM. Thenumber of specific binding sites for Ru360 was 6.2 pmol/mg protein. Ruthenium red and Ru360were mutually exclusive inhibitors. Bound La3+ was not displaced by Ru360. Rrphen was theleast effective for inhibiting calcium uptake. The results support the notion of a specific bindingsite in the uniporter for the polycationic complexes and a negative charged region from thephospholipids in the membrane, closely associated with the uniporter inhibitor-binding site.
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    URL: http://dx.doi.org/10.1023/A:1005464927366
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    A Connectionist Model of Left-Right Sound Discrimination by the Mauthner System (1999)
    Springer
    Journal of computational neuroscience 6 (1999), S. 121-144 
    Details
    ISSN: 1573-6873
    Keywords: Mauthner ; escape ; artificial neural networks ; connectionism ; acoustic ; localization ; auditory ; fish ; goldfish ; XNOR model ; phase model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine , Physics
    Notes: Abstract Artificial neural networks were used to explore the auditory function of the Mauthner system, the brainstem circuit in teleost fishes that initiates fast-start escape responses. The artificial neural networks were trained with backpropagation to assign connectivity and receptive fields in an architecture consistent with the known anatomy of the Mauthner system. Our first goal was to develop neurally specific hypotheses for how the Mauthner system discriminates right from left in the onset of a sound. Our model was consistent with the phase model for directional hearing underwater, the prevalent theory for sound source localization by fishes. Our second goal was to demonstrate how the neural mechanisms that permit sound localization according to the phase model can coexist with the mechanisms that permit the Mauthner system to discriminate between stimuli based on amplitude. Our results indicate possible computational roles for elements of the Mauthner system, which has provided us a theoretical context within which to consider past and future experiments on the cellular physiology. Thus, these findings demonstrate the potential significance of this approach in generating experimentally testable hypotheses for small systems of identified cells.
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    URL: http://dx.doi.org/10.1023/A:1008828501676
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    Structure and function of ferrochelatase (1995)
    Springer
    Journal of bioenergetics and biomembranes 27 (1995), S. 221-229 
    Details
    ISSN: 1573-6881
    Keywords: Heme ; porphyrin ; mitochondria ; iron-sulfur cluster ; heme metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Ferrochelatase is the terminal enzyme of the heme biosynthetic pathway in all cells. It catalyzes the insertion of ferrous iron into protoporphyrin IX, yielding heme. In eukaryotic cells, ferrochelatase is a mitochondrial inner membrane-associated protein with the active site facing the matrix. Decreased values of ferrochelatase activity in all tissues are a characteristic of patients with protoporphyria. Point-mutations in the ferrochelatase gene have been recently found to be associated with certain cases of erythropoietic protoporphyria. During the past four years, there have been considerable advances in different aspects related to structure and function of ferrochelatase. Genomic and cDNA clones for bacteria, yeast, barley, mouse, and human ferrochelatase have been isolated and sequenced. Functional expression of yeast ferrochelatase in yeast strains deficient in this enzyme, and expression inEscherichia coli and in baculovirusinfected insect cells of different ferrochelatase cDNAs have been accomplished. A recently identified (2Fe-2S) cluster appears to be a structural feature shared among mammalian ferrochelatases. Finally, functional studies of ferrochelatase site-directed mutants, in which key amino acids were replaced with residues identified in some cases of protoporphyria, will be summarized in the context of protein structure.
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    URL: http://dx.doi.org/10.1007/BF02110037
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    The irreversibility of inner mitochondrial membrane permeabilization by Ca2+ plus prooxidants is determined by the extent of membrane protein thiol cross-linking (1996)
    Springer
    Journal of bioenergetics and biomembranes 28 (1996), S. 523-529 
    Details
    ISSN: 1573-6881
    Keywords: Calcium ; cyclosporin A ; mitochondria ; mitochondrial permeability transition pore ; protein oxidation ; reactive oxygen species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract We have previously shown that mitochondrial membrane potential (δψ) drop promoted by prooxidants and Ca2+ can be reversed but not sustained by ethylene glycol-bis(β-aminoethylether)-N,N,N′,N′-tetraacetic acid (EGTA) unless dithiothreitol (DTT), a disulfide reductant, is also added [Valle, V. G. R., Fagian, M. M., Parentoni, L. S., Meinicke, A. R., and Vercesi, A. E. (1993).Arch. Biochem. Biophys. 307, 1–7]. In this study we show that catalase or ADP are also able to potentiate this EGTA effect. When EGTA is added long after (12 min) the completion of swelling or δψ elimination, no membrane resealing occurs unless the EGTA addition was preceded by the inclusion of DTT, ADP, or catalase soon after δψ was collapsed. Total δψ recovery by EGTA is obtained only in the presence of ADP. The sensitivity of the ADP effect to carboxyatractyloside strongly supports the involvement of the ADP/ATP carrier in this mechanism. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of solubilized membrane proteins shows that protein aggregation due to thiol cross-linkage formed during δψ drop continues even after δψ is already eliminated. Titration with 5,5′-dithio-bis(2-nitrobenzoic acid) supports the data indicating that the formation of protein aggregates is paralleled by a decrease in the content of membrane protein thiols. Since the presence of ADP and EGTA prevents the progress of protein aggregation, we conclude that this process is responsible for both increased permeability to larger molecules and the irreversibility of δΩ drop. The protective effect of catalase suggests that the continuous production of protein thiol cross-linking is mediated by mitochondrial generated reactive oxygen species.
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    URL: http://dx.doi.org/10.1007/BF02110442
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    Lineage-Specific Evolution of Echinoderm Mitochondrial ATP Synthase Subunit 8 (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 233-239 
    Details
    ISSN: 1573-6881
    Keywords: ATP synthase subunit 8 ; genes ; mammals ; mitochondria ; sea urchins ; sequences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Peculiar evolutionary properties of the subunit 8 of mitochondrial ATP synthase (ATPase8) are revealed by comparative analyses carried out between both closely and distantly related species of echinoderms. The analysis of nucleotide substitution in the three echinoids demonstrated a relaxation of amino acid functional constraints. The deduced protein sequences display a well conserved domain at the N-terminus, while the central part is very variable. At the C-terminus, the broad distribution of positively charged amino acids, which is typical of other organisms, is not conserved in the two different echinoderm classes of the sea urchins and of the sea stars. Instead, a motif of three amino acids, so far not described elsewhere, is conserved in sea urchins and is found to be very similar to the motif present in the sea stars. Our results indicate that the N-terminal region seems to follow the same evolutionary pattern in different organisms, while the maintenance of the C-terminal part in a phylum-specific manner may reflect the co-evolution of mitochondrial and nuclear genes.
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    URL: http://dx.doi.org/10.1023/A:1022406026196
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    Early Bioenergetic Changes in Hepatocarcinogenesis: Preneoplastic Phenotypes Mimic Responses to Insulin And Thyroid Hormone (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 303-313 
    Details
    ISSN: 1573-6881
    Keywords: Hepatic preneoplasia ; glycogenotic foci ; amphophilic foci ; mitochondria ; peroxisomes ; hepatocellular neoplasms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Biochemical and molecular biological approaches in situ have provided compelling evidence for early bioenergetic changes in hepatocarcinogenesis. Hepatocellular neoplasms regularly develop from preneoplastic foci of altered hepatocytes, irrespective of whether they are caused by chemicals, radiation, viruses, or transgenic oncogenes. Two striking early metabolic aberrations were discovered: (1) a focal excessive storage of glycogen (glycogenosis) leading via various intermediate stages to neoplasms, the malignant phenotype of which is poor in glycogen but rich in ribosomes (basophilic), and (2) an accumulation of mitochondria in so-called oncocytes and amphophilic cells, giving rise to well-differentiated neoplasms. The metabolic pattern of human and experimentally induced focal hepatic glycogenosis mimics the phenotype of hepatocytes exposed to insulin. The conversion of the highly differentiated glycogenotic hepatocytes to the poorly differentiated cancer cells is usually associated with a reduction in gluconeogenesis, an activation of the pentose phosphate pathway and glycolysis, and an ever increasing cell proliferation. The metabolic pattern of preneoplastic amphophilic cell populations has only been studied to a limited extent. The few available data suggest that thyromimetic effects of peroxisomal proliferators and hepadnaviral infection may be responsible for the emergence of the amphophilic cell lineage of hepatocarcinogenesis. The actions of both insulin and thyroid hormone are mediated by intracellular signal transduction. It is, thus, conceivable that the early changes in energy metabolism during hepatocarcinogenesis are the consequence of alterations in the complex network of signal transduction pathways, which may be caused by genetic as well as epigenetic primary lesions, and elicit adaptive metabolic changes eventually resulting in the malignant neoplastic phenotype.
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    URL: http://dx.doi.org/10.1023/A:1022438528634
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    Butylated hydroxytoluene and inorganic phosphate plus Ca2+ increase mitochondrial permeability via mutually exclusive mechanisms (1996)
    Springer
    Journal of bioenergetics and biomembranes 28 (1996), S. 199-206 
    Details
    ISSN: 1573-6881
    Keywords: Butylated hydroxytoluene ; mitochondria ; permeability transition ; phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Mitochondria undergo a permeability transition (PT), i.e., become nonselectively permeable to small solutes, in response to a wide range of conditions/compounds. In general, opening of the permeability transition pore (PTP) is Ca2+- and Pi-dependent and is blocked by cyclosporin A (CsA), trifluoperazine (TFP), ADP, and butylated hydroxytoluene (BHT). Gudz and coworkers have reported [7th European Bioenergetics Conference, EBEC Short Reports (1992)7, 125], however, that, under some conditions, BHT increases mitochondrial permeability via a process that may not share all of these characteristics. Specifically, they determined that the BHT-induced permeability transition was independent of Ca2+ and was insensitive to CsA. We have used mitochondrial swelling to compare in greater detail the changes in permeability induced by BHT and by Ca2+ plus Pi with the following results. (1) The dependence of permeability on BHT concentration is triphasic: there is a threshold BHT concentration (ca. 60 nmol BHT/ mg mitochondrial protein) below which no increase occurs; BHT enhances permeability in an intermediate concentration range; and at high BHT concentrations (〉 120 nmol/mg) permeability is again reduced. (2) The effects of BHT depend on the ratio of BHT to mitochondrial protein. (3) Concentrations of BHT too low to induce swelling block the PT induced by Ca2+ and Pi. (4) The dependence of the Ca2+-triggered PT on Pi concentration is biphasic. Below a threshold of 50–100 ΜM, no swelling occurs. Above this threshold swelling increases rapidly. (5) Pi levels too low to support the Ca2+-induced PT inhibit BHT-induced swelling. (6) Swelling induced by BHT can bestimulated by agents and treatments that block the PT induced by Ca2+ plus Pi. These data suggest that BHT and Ca2+ plus Pi, increase mitochondrial permeability via two mutually exclusive mechanisms.
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    URL: http://dx.doi.org/10.1007/BF02110651
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    Human Cytochrome c Oxidase: Structure, Function, and Deficiency (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 151-163 
    Details
    ISSN: 1573-6881
    Keywords: cytochrome c oxidase ; respiratory chain ; mitochondria ; assembly ; enzyme deficiency ; Leigh's syndrome ; mitochondrial myopathy (Saccharomyces cerevisiae, human)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract As the terminal component of the mitochondrial respiratory chain, cytochrome c oxidase plays a vital role in cellular energy transformation. Human cytochrome c oxidase is composed of 13 subunits. The three major subunits form the catalytic core and are encoded by mitochondrial DNA (mtDNA). The remaining subunits are nuclear-encoded. The primary sequence is known for all human subunits and the crystal structure of bovine heart cytochrome c oxidase has recently been reported. However, despite this wealth of structural information, the role of the nuclear-encoded subunits is still poorly understood. Yeast cytochrome c oxidase is a close model of its human counterpart and provides a means of studying the effects of mutations on the assembly, structure, stability and function of the enzyme complex. Defects in cytochrome c oxidase function are found in a clinically heterogeneous group of disorders. The molecular defects that underlie these diseases may arise from mutations of either the mitochondrial or the nuclear genomes or both. A significant number of cytochrome c oxidase deficiencies, often associated with other respiratory chain enzyme defects, are attributed to mutations of mtDNA. Mutations of mtDNA appear, nonetheless, uncommon in early childhood. Pedigree analysis and cell fusion experiments have demonstrated a nuclear involvement in some infantile cases but a specific nuclear genomic lesion has not yet been reported. Detailed analyses of the many steps involved in the biogenesis of cytochrome c oxidase, often pioneered in yeast, offer several starting points for further molecular characterizations of cytochrome c oxidase deficiencies observed in clinical practice.
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    The bifunctional cytochromec reductase/processing peptidase complex from plant mitochondria (1995)
    Springer
    Journal of bioenergetics and biomembranes 27 (1995), S. 423-436 
    Details
    ISSN: 1573-6881
    Keywords: Cytochromec reductase ; bc 1 complex ; respiratory chain ; mitochondrial processing peptidase ; protein import ; mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Cytochromec reductase from potato has been extensively studied with respect to its catalytic activities, its subunit composition, and the biogenesis of individual subunits. Molecular characterization of all 10 subunits revealed that the high-molecular-weight subunits exhibit striking homologies with the components of the general mitochondrial processing peptidase (MPP) from fungi and mammals. Some of the other subunits show differences in the structure of their targeting signals or in their molecular composition when compared to their counterparts from heterotrophic organisms. The proteolytic activity of MPP was found in the cytochromec reductase complexes from potato, spinach, and wheat, suggesting that the integration of the protease into this respiratory complex is a general feature of higher plants.
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    URL: http://dx.doi.org/10.1007/BF02110005
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    Cooperation of a “Reactive Oxygen Cycle” with The Q Cycle and The Proton Cycle in the Respiratory Chain—Superoxide Generating and Cycling Mechanisms in Mitochondria (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 367-376 
    Details
    ISSN: 1573-6881
    Keywords: Superoxide generation ; protonmotive force dependent ; protonophore ; proton leak ; heat production ; ROS cycle ; mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Based on our recent findings concerning the generating, partitioning, targeting, and functioningof superoxide in mitochondria, a hypothetical model involving a “reactive oxygen cycle” inthe respiratory chain has been proposed (Liu and Huang, 1991, 1996; Liu et al., 1996; Liu,1997, 1998) This model emphasizes that during State 4 respiration, an interaction between anelectron leak (a branch of electron transfer directly from the respiratory chain to form O•- 2,but not H2O) and a proton leak (a branch pathway which utilizes $$\Delta \mu _{{\text{H}}^{\text{ + }} } $$ to produce heat, butnot ATP) may take place in cooperation with the Q and proton cycles in mitochondria throughthe consumption of H+ by O•- 2 anions to form a protonated perhydroxyl radical, HO2, whichis directly permeable across the inner mitochondrial membrane and induces proton leakageand a decrease of $$\Delta \mu _{{\text{H}}^{\text{ + }} } $$ . O•- 2 generation in the mitochondrial respiratory chain and its cyclingacross the inner membrane may have the role of an endogenous protonophore in regulating andpartitioning energy transduction and heat production, as well as in pathogenesis of mitochondrialdiseases, aging, and apoptosis. The present article summarizes the supporting experimentalevidence obtained in this laboratory and presents a brief description of the theoretical basisof this model
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    URL: http://dx.doi.org/10.1023/A:1018650103259
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    Hexokinase Binding to Mitochondria: A Basis for Proliferative Energy Metabolism (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 331-338 
    Details
    ISSN: 1573-6881
    Keywords: Cancer ; proliferation ; Crabtree effect ; insulin action ; compartmentation ; aerobic glycolysis ; hexokinase ; mitochondria ; porin ; protein synthesis ; TCA cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Current thought is that proliferating cells undergo a shift from oxidative to glycolytic metabolism, where the energy requirements of the rapidly dividing cell are provided by ATP from glycolysis. Drawing on the hexokinase–mitochondrial acceptor theory of insulin action, this article presents evidence suggesting that the increased binding of hexokinase to porin on mitochondria of cancer cells not only accelerates glycolysis by providing hexokinase with better access to ATP, but also stimulates the TCA cycle by providing the mitochondrion with ADP that acts as an acceptor for phosphoryl groups. Furthermore, this acceleration of the TCA cycle stimulates protein synthesis via two mechanisms: first, by increasing ATP production, and second, by provision of certain amino acids required for protein synthesis, since the amino acids glutamate, alanine, and aspartate are either reduction products or partially oxidized products of the intermediates of glycolysis and the TCA cycle. The utilization of oxygen in the course of the TCA cycle turnover is relatively diminished even though TCA cycle intermediates are being consumed. With partial oxidation of TCA cycle intermediates into amino acids, there is necessarily a reduction in formation of CO2 from pyruvate, seen as a relative diminution in utilization of oxygen in relation to carbon utilization. This has been assumed to be an inhibition of oxygen uptake and therefore a diminution of TCA cycle activity. Therefore a switch from oxidative metabolism to glycolytic metabolism has been assumed (the Crabtree effect). By stimulating both ATP production and protein synthesis for the rapidly dividing cell, the binding of hexokinase to mitochondrial porin lies at the core of proliferative energy metabolism. This article further reviews literature on the binding of the isozymes of hexokinase to porin, and on the evolution of insulin, proposing that intracellular insulin-like proteins directly bind hexokinase to mitochondrial porin.
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    URL: http://dx.doi.org/10.1023/A:1022442629543
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    An alternative approach to electrochemistry (1995)
    Springer
    Journal of statistical physics 78 (1995), S. 513-529 
    Details
    ISSN: 1572-9613
    Keywords: Donnan potential ; electric potential ; electrochemical cell ; external electric work ; liquid junction potential ; mitochondria ; Onsager reciprocal relations ; operational quantities ; single-ion chemical potential ; state function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The concepts used conventionally in electrochemistry, single-ion chemical potential and electrostatic potential difference, are not obtainable from measurements in an inhomogeneous system. The use of nonoperational and mutually dependent forces in flux equations has impeded our understanding of electrochemical processes, and has led to wrong conclusions. The equation for entropy production is derived using only operationally defined quantities, chemical potentials of neutral components and the electric potential measured with reversible electrodes. The electric potential enters calculations as external electric work in the first law of thermodynamics. From entropy production, flux equations are obtained where the forces are operationally defined, measurable quantities. Three different problems from electrochemistry are discussed, the liquid junction potential, the Donnan potential, and energy coversion in mitochondria. The conventional method of calculations and the operational method are compared. The operational method permits more detailed calculations of emf, and an understanding of the process from a different approach.
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    URL: http://dx.doi.org/10.1007/BF02183362
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