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  • 1
    Electronic Resource
    Electronic Resource
    Evolution of the 14-3-3 Protein Family: Does the Large Number of Isoforms in Multicellular Organisms Reflect Functional Specificity? (2000)
    Springer
    Journal of molecular evolution 51 (2000), S. 446-458 
    Details
    ISSN: 1432-1432
    Keywords: Key words: 14-3-3 — Isoforms — Functional specificity — Affinity — H+ATPase — Phylogeny — Surface plasmon resonance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. 14-3-3 proteins constitute a family of eukaryotic proteins that are key regulators of a large number of processes ranging from mitosis to apoptosis. 14-3-3s function as dimers and bind to particular motifs in their target proteins. To date, 14-3-3s have been implicated in regulation or stabilization of more than 35 different proteins. This number is probably only a fraction of the number of proteins that 14-3-3s bind to, as reports of new target proteins have become more frequent. An examination of 14-3-3 entries in the public databases reveals 153 isoforms, including alleloforms, reported in 48 different species. The number of isoforms range from 2, in the unicellular organism Saccharomyces cerevisiae, to 12 in the multicellular organism Arabidopsis thaliana. A phylogenetic analysis reveals that there are four major evolutionary lineages: Viridiplantae (plants), Fungi, Alveolata, and Metazoa (animals). A close examination of the aligned amino acid sequences identifies conserved amino acid residues and regions of importance for monomer stabilization, dimer formation, target protein binding, and the nuclear export function. Given the fact that 53% of the protein is conserved, including all amino acid residues in the target binding groove of the 14-3-3 monomer, one might expect little to no isoform specificity for target protein binding. However, using surface plasmon resonance we show that there are large differences in affinity between nine 14-3-3 isoforms of A. thaliana and a target peptide representing a novel binding motif present in the C terminus of the plant plasma membrane H+ATPase. Thus, our data suggest that one reason for the large number of isoforms found in multicellular organisms is isoform-specific functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002390010107
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  • 2
    Electronic Resource
    Electronic Resource
    A genetic analysis of the role of calcineurin and calmodulin in Ca++-dependent improvement of NaCl tolerance of Saccharomyces cerevisiae (1996)
    Springer
    Current genetics 30 (1996), S. 476-484 
    Details
    ISSN: 1432-0983
    Keywords: Key words Calcineurin  ;  Calmodulin  ;  Saccharomyces cerevisiae  ;  Salt tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mutants of Saccharomyces cerevisiae lacking activity of the Ca2+/calmodulin-dependent protein phosphatase calcineurin, show sensitivity to high concentrations of sodium that is partly reversed by the external supply of Ca2+. On long-time exposure to NaCl stress the mutants display an increased intracellular Na+/K+ ratio which is partially corrected by the addition of Ca2+, improving the sodium efflux of not only calcineurin-defective cells but also wild-type cells. We also demonstrate that the NaCl sensitivity of cmd mutants, expressing modified forms of calmodulin that do not bind Ca2+, is strongly reversed by the addition of Ca2+. This effect is highly dependent on calcineurin, since the NaCl tolerance of a cmd1-3 strain, carrying an additional mutation in calcineurin, is only slightly assisted by Ca2+. A striking characteristic of the loss of function of calcineurin is a several-fold increased content of intracellular Ca2+, localized mainly in subcellular compartment(s). If the compartmentalized Ca2+ pool is brought back to normal levels by an additional inactivating mutation of the vacuolar Ca2+-transporting ATPase, such double mutants do not significantly improve their tolerance to NaCl.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002940050159
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  • 3
    Electronic Resource
    Electronic Resource
    Activation of 1,3-β-glucan synthase by Ca2+, spermine and cellobiose. – Localization of activator sites using inside-out plasma membrane vesicles (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 77 (1989), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The plant plasma membrane contains a 1,3-β-glucan synthase (EC 2.4.1.34) which has its active site on the cytoplasmic side of the membrane, while the product, the cell wall component callose, is deposited on the apoplastic side of the membrane. This enzyme should therefore be an integral, transmembrane protein. The activity of the enzyme is stimulated by Ca2+, polyamines, and polyols. Using sealed, inside-out (cytoplasmic side out) plasma membrane vesicles from sugar beet (Beta vulgaris L.) leaves, which permits the activity to be measured without solubilization of the membrane, we have localized the activator sites for Ca2+, spermine, and cellobiose to the cytoplasmic side of the plasma membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1989.tb04969.x
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  • 4
    Electronic Resource
    Electronic Resource
    Cytochromes of plant plasma membranes. Characterization by absorbance difference spectrophotometry and redox titration (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 76 (1989), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The cytochrome composition of plasma membranes (PM) obtained by phase partitioning of microsomal fractions from spinach leaves (Spinacea oleracea L. cv. Medania), cauliflower inflorescences (Brassica oleracea L.), sugar beer leaves (Beta vulgaris L.) and barley (Hordeum vulgare L. cv. Kristina) roots and leaves was characterized by absorbance difference spectrophotometry at different reducing conditions at 20 and – 196°C, by redox titration, and by heme staining of polypeptide bands after lithium dodecyl sulfate polyacrylamide gel electrophoresis (LDS-PAGE). The location of the α-bands in the difference spectra and the loss of heme after treatment with LDS indicated that predominantly cytochromes of the b-type were present in all species tested. The total concentration of cytochrome was ca 0.35 nmol (mg protein)−1. The main component (ca 70% of total) was completely reduced by ascorbate and partly by NADH and had a midpoint potential of ca 150 mV. At – 196°C, ascorbate reduction revealed a symmetrical α-band at ca 557 nm with PM from spinach leaves, cauliflower and sugar beet leaves, but with barley root and leaf PM ascorbate reduction resulted in an asymmetrical α-band (shoulder at 552, maximum at 559 nm). In the dithionite-reduced minus ascorbate-reduced spectrum at –196°C a split α-band (552 + 558 nm) was seen with PM from all species. This minor component had a midpoint potential of ca – 50 mV and is probably identical to cytochrome b5, the presence of which would explain the relatively high NADH-cytochrome c reductase activities observed with plant PM. With PM from cauliflower, CO-difference spectra indicated that cytochromes P-420 and P-450 were present at concentrations up to 0.06 and 0.03 nmol (mg protein)−1, respectively. Visualization of cytochromes by heme staining after LDS-PAGE was complicated by endogenous peroxidase activity and by loss of heme during solubilisation. A presumptive b-cytochrome (heme-stained band at 94 kDa) was only detected with barley leaf PM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1989.tb05621.x
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  • 5
    Electronic Resource
    Electronic Resource
    Isolation and polypeptide composition of l,3-ß-glucan synthase from plasma membranes of Brassica oleracea (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 81 (1991), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The l,3-ß-glucan synthase (callose synthase, EC 2.4.1.34) was solubilized from cauliflower (Brassica oleracea L.) plasma membranes with digitonin, and partially purified by ion exchange chromatography and gel filtration [fast protein liquid chromatography (FPLC)] using 3-[(cholamidopropyl)dimethylammonio]-1-propane-sulfonate (CHAPS) in the elution buffers. These initial steps were necessary to obtain specific precipitation of the enzyme during product entrapment, the final purification step. Five polypeptides of 32, 35, 57, 65 and 66 kDa were highly enriched in the final preparation and are thus likely components of the callose synthase complex. The purified enzyme was activated by Ca2+, spermine and cellobiose in the same way as the enzyme in situ, indicating that no essential subunits were missing. The polyglucan produced by the purified enzyme contained mainly 1,3-linked glucose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1991.tb08734.x
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  • 6
    Electronic Resource
    Electronic Resource
    NAD(P)H oxidase and peroxidase activities in purified plasma membranes from cauliflower inflorescences (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 71 (1987), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: An NAD(P)H oxidase activity stimulated by phenolic compounds has been investigated in purified plasma membranes (pm) and in an intracellular membrane (icm) fraction depleted in plasma membranes, both obtained from a microsomal fraction from cauliflower inflorescences (Brassica oleracea L.). The phenolic compounds salicylhydroxamic acid (SHAM), ferulic acid, coniferyl alcohol, n-propyl gallate, naringenin, kaempferol and caffeic acid all strongly stimulated the activity. Peroxidase (EC 1.11.1.7), or a peroxidase-like enzyme, was responsible for the NAD(P)H oxidase activity, which proceeded through a free-radical chain reaction and was inhibited by catalase (EC 1.11.1.6), superoxide dismutase (EC 1.15.1.1) and KCN. Most of the total activity was soluble; however, the membrane-bound activity was highly enriched in the pm compared to the icm. The catalase activity was 6 times higher in the icm-fraction than in the pm-fraction, but this was not the reason for the much lower phenol-stimulated NADH oxidase activity in the icm. Peroxidase activity measured with o-dianisidine and H2O2 had about the same specific activities in the pm-and icm-fractions.Neither the phenol-stimulated NADH oxidase nor the peroxidase activity could be washed away from the pm even by 0.7 M NaCl, indicating that these activities are truly membrane-bound. SHAM as well as the other phenolic compounds capable of stimulating the NADH oxidase reaction were potent inhibitors of blue light-induced cytochrome b-reduction in the pm fraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1987.tb04610.x
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  • 7
    Electronic Resource
    Electronic Resource
    Rapid purification of the plasma membrane H+-ATPase in its non-activated form using FPLC (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 92 (1994), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The plasma membrane H-ATPase (EC 3.1.6.35) was solubilized from isolated spinach (Spinacia oleracea) leaf plasma membranes using the detergent dodecyl-β-d-maltoside and subsequently purified to near homogeneity by ion exchange chromatography (FPLC). The enzyme purified in the presence of glycerol and ATP showed no loss in activity during 8 h on ice nor upon freezing at -80°C and thawing, and the recovery was up to 75%. Addition of a phospholipid mixture only marginally increased the activity, whereas addition of lysophosphalidylcholine (lyso-PC) resulted in a 2-fold increase in activity and a decrease in Km lor ATP from ca 300 μM to 100 μM. The membrane-bound and the purified H-ATPases showed very similar properties, also in their responses to lyso-PC. which is believed to activate the enzyme by displacement of its C-terminal inhibitory domain. Taken together, the data indicate that the H-ATPase is purified in a non-activated form suitable for regulatory studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb08826.x
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  • 8
    Electronic Resource
    Electronic Resource
    Biosynthesis of aromatic amino acids by highly purified spinach chloroplasts – Compartmentation and regulation of the reactions (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 68 (1986), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The ability of chloroplasts to synthesize aromatic amino acids from CO2 was investigated using highly purified, intact spinach (Spinacia oleracea L. cv. Viking II) chloroplasts and 14CO2. Incorporation of 14C into aromatic amino acids was very low, however, and this was assumed to be due to lack of phosphoenolpyruvate (PEP), one of the substrates for the shikimate/arogenate pathway leading to aromatic amino acids in chloroplasts. Therefore, the glycolytic enzymes phosphoglycerate mutase (EC 2.7.5.3) and enolase (EC 4.2.1.11) were added to the 14CO2 fixation medium in order to convert labelled 3-phosphoglycerate exported from the intact chloroplasts to 2-phosphoglycerate and PEP. In this way a part of the glycolytic pathway was reconstituted outside the chloroplasts to substitute for the cytoplasm lost on isolation. The presence of both enzymes in the medium increased incorporation of 14C into Tyr and Phe more than ten-fold and incorporation into Trp about two-fold, while total 13CO2 fixation rates were not affected. Our results suggest that chloroplasts do not contain phosphoglycerate mutase or enolase, and that, in vivo, PEP is synthesized in the cytoplasm and imported to the chloroplast stroma for the biosynthesis of aromatic amino acids. The biosynthesis of all three aromatic amino acids was under feedback control. Using expected physiological concentrations (below 100 μM), each of the aromatic amino acids exerted a strict feedback inhibition of its own biosynthesis only.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1986.tb03410.x
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  • 9
    Electronic Resource
    Electronic Resource
    Preparation and polypeptide composition of chlorophyll-free plasma membranes from leaves of light-grown spinach and barley (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 62 (1984), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Chlorophyf l-free preparations of plasma membranes from leaves of barley (Hordeum vulgare L. cv. Kristina) and spinach (Spinada oleracea L. cv. Viking II) were obtained by partition in an aqueous dextran-polyethylene glycol two-phase system. CJlu-can synthetase II (EC 2.4,1.34), a marker for the plasma membrane, was highly enriched in both preparations. Silicotungstic acid, a specific stain for the plasma membrane, indicated a purity close to 100% for the barley preparation. Both plasma membrane preparations contained a light-reducible b-cytochrome, as shown by low temperature spectroscopy. The plasma membranes had a tow protein content compared to the bulk of intracellular membranes. The polypeptide composition of the barley and spinach plasma membranes showed striking similarities, with.the most prominent polypeptides in the 49-58 kdalton region, and some further prominent bands in the 30 kcialton region. Some high molecular weight polypeptides in the 73-110 kdalton region were also typical for the plasma membranes compared to the microsomal fractions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1984.tb02791.x
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  • 10
    Electronic Resource
    Electronic Resource
    On the presence of inside-out plasma membrane vesicles and vanadate-inhibited K+,Mg2+-ATPase in microsomal fractions from wheat and maize roots (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 77 (1989), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We have estimated the amount of inside-out plasma membrane (PM) vesicles in microsomal fractions from wheat (Triticum aestivum L. cv. Drabant) and maize (Zea mays L.) roots; non-latent activities of the PM markers vanadate-inhibited K+, Mg2+-ATPase (ΔVO4-ATPase) and glucan synthase II (GS II, EC 2.4.1.34) were used as markers for inside-out PM vesicles, latent activities as markers for right-side-out PM vesicles, and specific staining with silicotungstic acid (STA) as a general marker for the PM. Separation of presumptive inside-out PM vesicles from right-side-out ones was achieved by counter-current-distribution (CCD) in an aqueous polymer two-phase system. Most of the GS II activity was latent and was found in material partitioning into the upper phase; a distribution which correlated well with that of STA-stained vesicles. Thus, most of the PM vesicles had a right-side-out orientation. ΔVO4-ATPase, on the other hand, had a dual distribution (particularly pronounced in wheat) and was recovered both in material partitioning into the lower phase and into the upper phase. This indicates that ΔVO4-ATPase activity was present also in membranes other than the PM. Additional evidence for this interpretation came from sucrose gradient centrifugation of wheat root material. This produced two peaks of ΔVO4-ATPase activity with the membranes partitioning into the lower phase, none of which coincided with the peak obtained with right-side-out PM vesicles. Taken together, these results indicate that only very few inside-out PM vesicles are present in the microsomal fraction, and that ΔVO4-ATPase as a marker for the PM, in contrast to GS II, may give quite misleading results with some plant materials. This stresses the need to use well-defined preparations of scaled, inside-out PM vesicles in solute uptake studies. The distribution of Ca2+-inhibited ATPase, on the other hand, agreed well with those of GS II and STA-stained vesicles both after CCD and sucrose gradient centrifugation, which suggests that Ca2+ inhibition may be a more specific property of the PM H+-ATPase than vanadate inhibition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1989.tb05971.x
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