Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Plasma membranes were isolated using the aqueous polymer two-phase partition method from the algae Chara corallina and Chara longifolia, algae which differ in their ability to grow in saline environments. Enrichment of plasma membrane and depletion of tonoplast relative to the microsomal fraction was monitored using phosphohydrolase assays and cross-reactions to antibodies raised against higher plant transporters. Antibodies to the vacuolar ATPase and pyrophosphatase cross-reacted with epitopes in the microsomal fraction, but showed little affinity for the plasma membrane fraction. Pyrophosphatase activity also declined in the plasma membrane fraction relative to the microsomal fraction. The V-type H(+)-ATPase activity, sensitive to nitrate or bafilomycin, was low in both fractions, though the cross-reaction to the antibody was reduced in the plasma membrane fraction. By contrast, the antibody recognition of a P-type H(+)-ATPase amino acid sequence from Arabidopsis did not occur strongly in the anticipated 90-100 kDa range. While there was enhanced recognition of a polypeptide at around 140 kDa in the plasma membrane fraction, salt treatment of Chara longifolia resulted in plasma membrane fractions with reduced amounts of this epitope, but no change in vanadate-sensitive ATPase activity, suggesting that it does not represent the only P-type ATPase. Microsomal membranes from salt-adapted C. longifolia have higher reactivity with the antibody to the tonoplast ATPase.
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PMID:Plasma membrane isolation from freshwater and salt-tolerant species of Chara: antibody cross-reactions and phosphohydrolase activities. 1153

The plant vacuolar proton pump can be subjected to reversible redox regulation in vitro. The redox-dependent activity change involves disulfide bridge formation not only in Vatp A, as reported for bovine V-ATPase, but also in the stalk subunit Vatp E. Microsomal membranes isolated from barley leaves were analysed for their activity of bafilomycin-sensitive ATP hydrolysis and proton pumping using quinacrine fluorescence quenching in vesicle preparations. ATP hydrolysis and proton pumping activity were inhibited by H2O2. H2O2-deactivated ATPase was reactivated by cysteine and glutathione. The glutathione concentration needed for half maximal reactivation was 1 mmol l-1. The activity loss was accompanied by shifts in electrophoretic mobility of Vatp A and E which were reversed upon reductive reactivation. The redox-dependent shift was also seen with recombinant Vatp E, and was absent following site-directed mutagenesis of either of the two cys residues conserved throughout all plant Vatp E sequences. V-ATPase was also inhibited by oxidized thioredoxin. These results support the hypothesis that tuning of vacuolar ATPase activity can be mediated by redox control depending on the metabolic requirements.
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PMID:Reversible redox control of plant vacuolar H+-ATPase activity is related to disulfide bridge formation in subunit E as well as subunit A. 1169 86

It was recently shown that vacuolar ATPase and mitochondrial F1F0-ATPase activities are induced by aluminum (Al) in an Al-resistant cultivar of wheat, suggesting that induction of these enzymes could be an adaptive trait involved in Al resistance. To test this hypothesis, we used the Saccharomyces cerevisiae model system. In yeast, unlike wheat, the activity, transcript and protein levels of mitochondrial F1F0-ATPase, but not vacuolar ATPase, are induced by Al, while plasma membrane P-ATPase activity is inhibited. However, yeast vacuolar ATPase mutant strains are hypersensitive to Al, while F1F0-ATPase mutant strains exhibit wild-type growth. These data suggest that vacuolar ATPase activity is involved in Al resistance, with ATP required for this activity supplied by mitochondrial F1F0-ATPase or fermentation.
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PMID:Vacuolar H+-ATPase, but not mitochondrial F1F0-ATPase, is required for aluminum resistance in Saccharomyces cerevisiae. 1175 Aug 8

The proton-translocating vacuolar ATPase (V-ATPase) acidifies the endocytic network of eukaryotic cells. Although all eukaryotic cell types require low to moderate levels of V-ATPase, some proton-secreting cells express amplified levels for use in specialized membrane domains. To characterize genetic elements required for this heightened expression, we studied transcription and stability of mRNA encoding the V-ATPase c subunit in a low expressing fibroblast cell line (NIH 3T3) and a high expressing macrophage cell line (RAW 264.7). Isolation of the promoter and mapping of the transcriptional start site indicated that the c subunit promoter is TATA-less and initiates transcription at a single site. Promoter activity was regulated through the same transcription factor binding sites in both cell types, which showed no discernible difference in rates of c subunit transcription. In contrast, c subunit transcripts showed markedly greater stability in RAW cells than in 3T3 cells, as did other constitutively expressed V-ATPase subunit transcripts. Only the B and 'a' subunits, which are expressed in multiple isoforms, were not regulated solely by mRNA stability. These results suggest that overall expression levels of the V-ATPase are set primarily by regulation of mRNA stability and that transcriptional mechanisms determine subunit composition in varying cell types.
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PMID:Regulation of enhanced vacuolar H+-ATPase expression in macrophages. 1178 55

Salt tolerance in Saccharomyces cerevisiae is a complex trait, involving regulation of membrane polarization, Na(+) efflux and sequestration of Na(+) in the vacuole. Since transmembrane transport energized by H(+)-adenosine triphosphatases (ATPases) is common to all of these tolerance mechanisms, the objective of this study was to characterize the responses of the plasma membrane H(+)-ATPase, vacuolar H(+)-ATPase and mitochondrial F(1)F(0)-ATPase to NaCl stress. We hypothesized that since the vacuolar ATPase is responsible for generating the proton motive force required for import of cations (such as Na(+)) into the vacuole, strains lacking this activity should be hypersensitive to NaCl. We found that strains lacking vacuolar ATPase activity were in fact hypersensitive to NaCl, while strains lacking ATP synthase were not. This effect was specific to the ionic component of NaCl stress, since the mutant strains were indistinguishable from wild-type and complemented strains in the presence of sorbitol.
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PMID:Vacuolar H(+)-ATPase, but not mitochondrial F(1)F(0)-ATPase, is required for NaCl tolerance in Saccharomyces cerevisiae. 1195 41

The vacuolar ATPase (V-ATPase) is a multisubunit enzyme that facilitates the acidification of intracellular compartments in eukaryotic cells and plays an important role in receptor-mediated endocytosis, intracellular trafficking processes, and protein degradation. In this study we show that the C-terminal fragment of 350 residues of the regulatory subunit H (V1H) of the V-ATPase shares structural and functional homologies with the beta-chains of adaptor protein complexes. Moreover, the fragment is similar to a region in the beta-subunit of COPI coatomer complexes, which suggests the existence of a shared domain in these three different families of proteins. For beta-adaptins, this fragment binds to cytoplasmic di-leucine-based sorting motifs such as in HIV-1 Nef that mediate endocytic trafficking. Expression of this fragment in cells blocks the internalization of transmembrane proteins, which depend on di-leucine-based motifs, whereas mutation of the consensus sequence GEY only partly diminishes the recognition of the sorting motif. Based on recent structural analysis, our results suggest that the di-leucine-binding domain consists of a HEAT or ARM repeat protein fold.
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PMID:Subunit H of the V-ATPase involved in endocytosis shows homology to beta-adaptins. 1205 68

At the onset of nutrient limitation, the yeast Saccharomyces cerevisiae synthesizes glycogen to serve as a carbon and energy reserve. We undertook a systematic survey for the genes that affect glycogen accumulation by taking advantage of the strain deletion set generated by the Saccharomyces Genome Deletion Project. The strain collection analyzed contained some 4600 diploid homozygous null deletants, representing approximately 88% of all viable haploid disruptants. We identified 324 strains with low and 242 with elevated glycogen stores, accounting for 12.4% of the genes analyzed. The screen was validated by the identification of many of the genes known already to influence glycogen accumulation. Many of the mutants could be placed into coherent families. For example, 195 or 60% of the hypoaccumulators carry mutations linked to respiratory function, a class of mutants well known to be defective in glycogen storage. The second largest group consists of approximately 60 genes involved in vesicular trafficking and vacuolar function, including genes encoding 13 of 17 proteins involved in the structure or assembly of the vacuolar ATPase. These data are consistent with our recent findings that the process of autophagy has a significant impact on glycogen storage (Wang, Z., Wilson, W. A., Fujino, M. A., and Roach, P. J. (2001) Antagonistic controls of autophagy and glycogen accumulation by Snf1p, the yeast homolog of AMP-activated protein kinase, and the cyclin-dependent kinase Pho85p. Mol. Cell. Biol. 21, 5742-5752). Autophagy delivers glycogen to the vacuole, and we propose that the impaired vacuolar function associated with ATPase mutants (vma10 or vma22) results in reduced degradation and subsequent hyperaccumulation of glycogen.
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PMID:Systematic identification of the genes affecting glycogen storage in the yeast Saccharomyces cerevisiae: implication of the vacuole as a determinant of glycogen level. 1209 23

Changes in the properties of extractable vacuolar H+-pumping pyrophosphatase (V-PPase) and vacuolar ATPase activities in chilling-sensitive seedlings of mung bean (Vigna radiata) were investigated. Following chilling at 4[deg]C for 48 h, both hydrolytic and proton-pumping activities of the V-PPase increased 1.5- to 2-fold over controls and remained elevated even after 72 h at low temperatures. Vacuolar ATPase levels did not change significantly throughout the chilling regime. However a large increase in alcohol dehydrogenase activity during chilling suggests a shift toward fermentative metabolism, which can be expected to decrease ATPase activity in situ. Western blotting of vacuolar membrane-enriched fractions from control and treated plants has confirmed that the changes in V-PPase activity are mirrored by increases in the amount of pump protein. Results suggest a specific role for the V-PPase in protecting chill-sensitive plants from the injurious effects of low temperatures via the maintenance of the proton gradient across the vacuolar membrane.
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PMID:Chill-Induced Changes in the Activity and Abundance of the Vacuolar Proton-Pumping Pyrophosphatase from Mung Bean Hypocotyls. 1222 20

The yeast vacuolar ATPase (V-ATPase) contains three proteolipid subunits: c (Vma3p), c' (Vma11p), and c" (Vma16p). Each subunit contains a buried glutamate residue that is essential for function, and these subunits are not able to substitute for each other in supporting activity. Subunits c and c' each contain four putative transmembrane segments (TM1-4), whereas subunit c" is predicted to contain five. To determine whether TM1 of subunit c" serves an essential function, a deletion mutant of Vma16p was constructed lacking TM1 (Vma16p-Delta TM1). Although this construct does not complement the loss of Vma3p or Vma11p, it does complement the loss of full-length Vma16p. Vacuoles isolated from the strain expressing Vma16p-Delta TM1 showed V-ATPase activity and proton transport greater than 80% relative to wild type and displayed wild type levels of subunits A and a, suggesting normal assembly of the V-ATPase complex. These results suggest that TM1 of Vma16p is dispensable for both activity and assembly of the V-ATPase. To obtain information about the topology of Vma16p, labeling of single cysteine-containing mutants using the membrane-permeable reagent 3-(N-maleimidylpropionyl)biocytin (MPB) and the -impermeable reagent 4-acetamido-4'-maleimidylstilbene-2,2'-disulfonic acid (AMS) was tested. Both the Cys-less form of Vma16p and eight single cysteine-containing mutants retained greater than 80% of wild type levels of activity. Of the eight mutants tested, two (S5C and S178C) were labeled by MPB. MPB-labeling of S5C was blocked by AMS in intact vacuoles, whereas S178C was blocked by AMS only in the presence of permeabilizing concentrations of detergent. In addition, a hemagglutinin epitope tag introduced into the C terminus of Vma16p was recognized by an anti-hemagglutinin antibody in intact vacuolar membranes, suggesting a cytoplasmic orientation for the C terminus. These results suggest that subunit c" contains four rather than five transmembrane segments with both the N and C terminus on the cytoplasmic side of the membrane.
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PMID:The first putative transmembrane segment of subunit c" (Vma16p) of the yeast V-ATPase is not necessary for function. 1248 75

Glial cell line-derived neurotrophic factor (GDNF) was reported to be effective for treating subjects with neurodegenerative diseases such as Parkinson's disease. In search of finding a compound which promotes GDNF secretion, we found that concanamycin A (ConA), a vacuolar ATPase (V-type ATPase) inhibitor purified from Streptomyces diastatochromogens, enhanced GDNF secretion from glioma cells. The rat glioma cell line, C6, and the human glioma cell lines, U87MG and T98G, abundantly expressed GDNF mRNA, and secreted GDNF into culture media, and this event was potently enhanced by a Ca(2+) ionophore and by phorbol ester, as noted in other cells. ConA concentration dependently and potently increased GDNF release from C6, U87MG and T98G cells into culture media. In addition, ConA enhanced GDNF secretion from astrocyte primary cultures prepared from the human fetus with the same potency seen in glioma cell lines. Likewise, another V-type ATPase inhibitor, bafilomycinA1 facilitated GDNF release from C6, U87MG and T98G glioma cells, in a concentration-dependent manner. The potencies of these V-type ATPase inhibitors in enhancing GDNF secretion were consistent with those which inhibited V-type ATPase activity. These results suggest that blockade of V-type ATPase potently stimulates the secretion of GDNF from glial cells. The V-type ATPase inhibitors may be beneficial to use for the treatment of diseases in which increase in GDNF could be effective.
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PMID:Increase in secretion of glial cell line-derived neurotrophic factor from glial cell lines by inhibitors of vacuolar ATPase. 1254 48


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