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  • 1
    Electronic Resource
    Electronic Resource
    Identification of anion and cation pathways in the inner mitochondrial membrane by patch clamping of mouse liver mitoplasts (1991)
    Springer
    The journal of membrane biology 124 (1991), S. 151-158 
    Details
    ISSN: 1432-1424
    Keywords: ion transport ; inner mitochondrial membrane channel ; propranolol ; amiodarone ; patch clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Alkalinization of the matrix side of the mitochondrial inner membrane by pH shifts from 6.8 to 8.3 caused a reversible increase in current of 3.2±0.2 pA (mean±se,n=21) at±40 mV measured using patch-clamp techniques. The current increase was reversed in a graded fashion by the addition of Mg2+ in 0.15m KCl corresponds to approximately 15 pS. Reversal potentials derived from whole patch currents indicated that the inner mitochondrial membrane was primarily cation selective at pH 6.8 with aP k/P Cl=32 (n=6). Treatment with alkaline pH (8.3) increased the current and anion permeability (P K/P Cl=16,n=6). The membrane becomes completely cation selective when low concentrations (12 μm) of the drug propranolol are added. The amphiphilic drugs amiodarone (4 μm), propranolol (70 μm) and quinine (0.6mm) blocked almost all of the current. The pH-dependent current was also inhibited by tributyltin. These results are consistent with the presence of two pathways in the inner mitochondrial membrane. One is cation selective and generally open and the other is anion selective and induced by alkaline pH. The alkaline pH-activated channel likely corresponds to the inner membrane anion channel postulated by others from suspension studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870459
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  • 2
    Electronic Resource
    Electronic Resource
    MCC and PSC, the Putative Protein Import Channels of Mitochondria (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 47-54 
    Details
    ISSN: 1573-6881
    Keywords: Protein import ; mitochondria ; MCC ; PSC ; import pore ; protein-translocating channels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract All but a small fraction of the hundreds of proteins in a mitochondrion are synthesized in thecytoplasm and imported into the organelle. Water-filled channels are integral to the process oftranslocating proteins since channels can provide an aqueous pathway through the hydrophobicenvironment of the membrane. The MCC (multiple conductance channel) and PSC(peptide-sensitive channel) are two high-conductance channels previously identified inelectrophysiological studies of mitochondrial membranes. MCC and PSC are the putative pores of the importcomplexes of the inner and outer membranes, respectively. The genetic, biochemical, andbiophysical evidence regarding these assignments are summarized herein. These findingssupport the identification of MCC and PSC as the protein import channels of mitochondria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005560328334
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  • 3
    Electronic Resource
    Electronic Resource
    Perspectives on the mitochondrial multiple conductance channel (1996)
    Springer
    Journal of bioenergetics and biomembranes 28 (1996), S. 115-123 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; multiple conductance channel ; mitochondrial megachannel ; permeability transition ; protein import ; peptide-sensitive channel ; intracellular channel ; patch clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract A multiple conductance channel (MCC) with a peak conductance of over 1 nS is recorded from mitoplasts (mitochondria with the inner membrane exposed) using patch-clamp techniques. MCC shares many general characteristics with other intracellular megachannels, many of which are weakly selective, voltage-dependent, and calcium sensitive. A role in protein import is suggested by the transient blockade of MCC by peptides responsible for targeting mitochondrial precursor proteins. MCC is compared with the peptide-sensitive channel of the outer membrane because of similarities in targeting peptide blockade. The pharmacology and regulation of MCC by physiological effectors are reviewed and compared with the properties of the pore hypothesized to be responsible for the mitochondrial inner membrane permeability transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02110641
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  • 4
    Electronic Resource
    Electronic Resource
    The Mitochondrial Protein Import Pathway: Are Precursors Imported through Membrane Channels? (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 3-10 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; MCC ; PSC ; import pathway ; membrane channels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Mitochondrial biogenesis requires the import of hundreds of different proteins from the cytosol. Protein import into mitochondria is a multistep pathway that includes recognition of precursor proteins by machinery both in the cytoplasm and on the mitochondrial surface, translocation of the precursor across one or both mitochondrial membranes, and folding of the protein after its import into the organelle. Over the past several years, many components of the import machinery have been identified using both biochemical and genetic methods. Recently, significant progress has been made determining the function of some of these import proteins. One purpose of this minireview is to summarize our current understanding of the import pathway, and to introduce the topics of the minireviews that will follow. The other goal of this minireview is to discuss recent findings suggesting that proteins are translocated across both the mitochondrial inner and outer membranes through aqueous channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022470303365
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  • 5
    Electronic Resource
    Electronic Resource
    Properties of channels in the mitochondrial outer membrane (1989)
    Springer
    Journal of bioenergetics and biomembranes 21 (1989), S. 451-459 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondrial outer membrane ; mitochondrial channels ; patch clamping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Patch-clamping studies with native outer mitochondrial membranes show a complex behavior. In the range of potentials in which the polarity of the pipette is positive, the behavior resembles that of VDAC incorporated into bilayers. Accordingly, there is a decrease in conductance with voltage. An involvement of VDAC is also supported by responses of the patches to the presence of polyanion or treatment with succinic anhydride, both of which affect VDAC. In contrast, in the negative range of potential, the conductance of the patches generally increases with the magnitude of the voltage. The increase in conductance shows a biphasic time course which is consistent with a model in which channels are first activated (first phase) and then assembled into larger high-conductance channels (second phase). A variety of experiments support the notion that an assembly takes place. The time course of the conductance increase is consistent with formation of the second-phase channels from 6±1 subunits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00762517
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  • 6
    Electronic Resource
    Electronic Resource
    Mitochondrial channel activity studied by patch-clamping mitoplasts (1989)
    Springer
    Journal of bioenergetics and biomembranes 21 (1989), S. 497-506 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondrial channels ; inner mitochondrial membrane ; channels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Patch-clamping mitoplasts, we have observed a complex pattern of conductance transitions. This report discusses primarily the 45, 120–150, 350, and 1,000 pS transitions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00762521
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  • 7
    Electronic Resource
    Electronic Resource
    Modulation of inner mitochondrial membrane channel activity (1992)
    Springer
    Journal of bioenergetics and biomembranes 24 (1992), S. 99-110 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; channels ; mitochondrial inner membrane ; pharmacology ; patch clamp ; inner membrane anion channel ; permeability transition pore
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Three classes of inner mitochondrial membrane (IMM) channel activities have been defined by direct measurement of conductance levels in membranes with patch clamp techniques in 150 mM K Cl. The “107 pS activity” is slightly anion selective and voltage dependent (open with matrix positive potentials). “Multiple conductance channel” (MCC) activity includes several levels from about 40 to over 1000 pS and can be activated by voltage or Ca2+. MCC may be responsible for the Ca2+-induced permeability transition observed with mitochondrial suspensions. A “low conductance channel” (LCC) is activated by alkaline pH and inhibited by Mg2+. LCC has a unit conductance of about 15 pS and may correspond to the inner membrane anion channel, IMAC, which was proposed from results obtained from suspension studies. All of the IMM channels defined thus far appear to be highly regulated and have a low open probability under physiological conditions. A summary of what is known about IMM channel regulation and pharmacology is presented and possible physiological roles of these channels are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00769536
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  • 8
    Electronic Resource
    Electronic Resource
    Voltage activation of heart inner mitochondrial membrane channels (1992)
    Springer
    Journal of bioenergetics and biomembranes 24 (1992), S. 119-124 
    Details
    ISSN: 1573-6881
    Keywords: Inner mitochondrial membrane ; channels ; voltage activation ; assembly ; cyclosporin ; patch-clamp ; permeability transition pore
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The patch clamp records obtained from mitoplast membranes prepared in the presence of a calcium chelator generally lack channel activity. However, multiconductance channel (MCC) activity can be induced by membrane potentials above ±60mV [Kinnallyet al., Biochem. Biophys. Res. Commun. 176, 1183–1188 (1991)]. Once activated, the MCC activity persists at all voltages. The present report characterizes the activation by voltage of multiconductance channels of rat heart inner mitochondrial membranes using patch-clamping. In some membrane patches, the size of single current transitions progressively increases with time upon application of voltage. The inhibitor cyclosporin has also been found to decrease channel conductance in steps. The results suggest that voltage-induced effects which are inhibited by cyclosporin Aare likely to involve either an increase in effective pore diameter or the assembly of low-conductance units. In activated patches, we have found at high membrane potentials (e.g., 130 mV) changes in conductance as high as 5 nS occurring in large steps (up to 2.7 nS). These were generally preceded by a smaller transition. Similar results were obtained less frequently at lower voltages. These results can be explained on the assumption that once assembled the channels may act in unison.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00769538
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of Carbonyl Cyanide Phenylhydrazones on Two Mitochondrial Ion Channel Activities (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 223-231 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; uncouplers ; channels ; patch-clamp ; MCC ; mCS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The respiratory uncouplers carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) and carbonyl cyanide m-chlorophenylhydrazone (CCCP) affect the activities of two mitochondrial ion channels from mouse liver. At micromolar concentrations, the phenylhydrazones block the voltage-dependent 100-pS channel, mCS, and induce the multiple-conductance-level channel, MCC. The binding site(s) involved in perturbation of channel activities are probably distinct from the sites involved in uncoupling of oxidative phosphorylation which occurs at nanomolar concentrations of the phenylhydrazones. The effects of FCCP and CCCP on the mitochondrial ion channels could be partially reversed by washing with fresh media and were always reversed by perfusion with dithiothreitol. These results indicate that the effects of the phenylhydrazones on mitochondrial ion channels may be related to the ability of these compounds to act as sulfhydryl reagents and not to their protonophoric and uncoupling activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022453809357
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  • 10
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    A fluorescence assay for peptide translocation into mitochondria (2007)
    Elsevier
    Details
    Publication Date: 2007-03-01
    Print ISSN: 0003-2697
    Electronic ISSN: 1096-0309
    Topics: Biology , Chemistry and Pharmacology
    Published by Elsevier
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