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)

The retinal pigment epithelium (RPE) is able to perform a variety of functions because of its high degree of plasma membrane polarity. Some aspects of this polarity such as the localization of the majority of Na-K ATPase to the apical membrane distinguish the RPE from kidney cells and most other transporting epithelia. The polarized budding of enveloped viruses such as vesicular stomatitis and influenza from the basolateral and apical membrane, respectively, has been used to study mechanisms underlying the domain-specific sorting of membrane proteins in cultured epithelial cell lines. These processes also serve as a useful index of the degree of polarization in epithelial cell cultures. Viral budding from apical and basolateral RPE membranes was used in this study to determine whether the sorting of viral envelope membrane proteins by the RPE is reversed in polarity from that of kidney cells and, if so, whether this might predict a fundamental difference in membrane protein sorting for RPE. The results clearly indicate that the polarity of viral membrane sorting and subsequent viral budding is the same in RPE as in other polarized epithelial cell lines examined to date.
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PMID:Polarized budding of vesicular stomatitis and influenza virus from cultured human and bovine retinal pigment epithelium. 133 32

The effect of erythropoietin (Ep), a glycoprotein hormone, has been studied on lipid peroxidation induced by Cu2+ and ascorbate in vitro, Mg2+ ATPase activity and spectrin of RBC membrane. Our present investigation reveals that Cu2+ and ascorbic acid increases lipid peroxidation of RBC membrane significantly. It has further been observed that under the same experimental condition spectrin, a major cytoskeleton membrane protein, and Mg(2+)-ATPase activity of RBC membrane decrease significantly. However, exogenous administration of Ep completely restores lipid peroxidation and Mg(2+)-ATPase activity and partially recovers spectrin of RBC membrane.
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PMID:Effect of Cu(2+)-ascorbic acid on lipid peroxidation, Mg(2+)-ATPase activity and spectrin of RBC membrane and reversal by erythropoietin. 133 13

Membrane Ca(2+)-ATPase activity was stimulated in vitro separately by T4 (10(-10) M) and by epinephrine (10(-6) M). In the presence of a fixed concentration of T4, additions of 10(-8) and 10(-6) M epinephrine reduced the T4 effect on the enzyme. beta-Adrenergic blockade with propranolol (10(-6) M) prevented stimulation by epinephrine of Ca(2+)-ATPase activity, but did not prevent the suppressive action of epinephrine on T4-stimulable Ca(2+)-ATPase. In contrast, alpha 1-adrenergic blockade with unlabelled prazosin restored the effect of T4 on Ca(2+)-ATPase activity in the presence of epinephrine. Like propranolol, prazosin prevented enhancement of enzyme activity by epinephrine in the absence of thyroid hormone. Neither prazosin nor propranolol had any effect on the stimulation by T4 of red cell Ca(2+)-ATPase in the absence of epinephrine. Analysis of radiolabelled prazosin binding to human red cell membranes revealed the presence of a single class of high-affinity binding sites (Kd, 1.2 x 10(-8) M; Bmax, 847 fmol/mg membrane protein). Thus, the human erythrocyte membrane contains alpha 1-adrenergic receptor sites that are capable of regulating Ca(2+)-ATPase activity.
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PMID:The alpha 1-adrenergic receptor in human erythrocyte membranes mediates interaction in vitro of epinephrine and thyroid hormone at the membrane Ca(2+)-ATPase. 133 72

The effect of large and small doses of rabbit antibodies specific to plasma membranes of the rat testicle cells has been studied in the experiments on Wistar rats of three age groups (preadolescent--aged 20 days, puberal--aged 5-7 months and old--aged 24-26 months). It is stated that incubation of plasma membranes by IgG fraction isolated from antimembrane testicular serum (IgG-ATCSm) in a large dose (43 g of protein G per 125 g of protein of membrane fraction) caused statistically reliable inhibition of Na+, K(+)-ATPase activity in the membranes of testicle cells of puberal and old rats. Preadolescent rats exhibit only a tendency to decrease the activity of this enzyme. Incubation of plasma membranes of testicle cells in rats of different age by small doses of IgG-ATCSm (0.43 g of protein G per 125 g of membrane protein) induced a statistically reliable increase of Na+, K(+)-ATPase activity in puberal and old animals and its slight increase in preadolescent rats. The IgG fraction isolated from normal rabbit serum (IgG-NRS) exerted a less pronounced effect on Na+, K(+)-ATPase activity parallel with retention of a tendency to a decrease of activity under the influence of large doses of the drug and to an increase with introduction of small doses.
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PMID:[The effect of antimembrane testicular antibodies on Na+, K(+)-ATPase activity in the testicles of rats of different ages]. 133 19

In vitro studies of multidrug-resistant cell lines have shown that a membrane protein, the P-glycoprotein, is responsible for resistance to a wide range of structurally and functionally dissimilar anti-cancer drugs. The amino-acid sequence of P-glycoprotein (Pgp) indicates two consensus sequences for ATP binding and the purified protein has been reported to possess a low level of ATPase activity. As part of our goal to further characterize the ATPase activity of P-glycoprotein, we have developed a procedure for rapid partial purification of the protein in a highly active form. Plasma membrane vesicles from multidrug-resistant CHRC5 Chinese hamster ovary cells were subjected to a two-step procedure involving selective extraction with different concentrations of the zwitterionic detergent CHAPS. The resulting extract was enriched in P-glycoprotein (around 30% pure) and displayed an ATPase activity (specific activity 543 nmol mg-1 min-1) that was not found in a similar preparation from drug-sensitive cells. The ATPase specific activity was over 10-fold higher than that previously reported for immunoprecipitated Pgp and 280-fold higher than that of immunoaffinity-purified Pgp. This ATPase activity could be distinguished from that of other ion-motive ATPases and membrane-associated phosphatases and is, thus, proposed to be directly attributable to P-glycoprotein. Optimal P-glycoprotein ATPase activity required Mg2+ at an ATP: Mg2+ molar ratio of 0.75:1 and the apparent Km for ATP was 0.88 mM. P-Glycoprotein ATPase could be completely inhibited by vanadate and by the sulfhydryl-modifying reagents N-ethylmaleimide, HgCl2 and p-chloromercuribenzenesulfonate. Certain drugs and chemosensitizers, including colchicine, progesterone, nifedipine, verapamil and trifluoperazine, produced up to 50% activation of P-glycoprotein ATPase activity.
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PMID:ATPase activity of partially purified P-glycoprotein from multidrug-resistant Chinese hamster ovary cells. 135 66

Although there is extensive data available on Ca2+ effects in normal tissues, comparatively little is known about its effects or regulation in tumor cells. The present studies were undertaken to investigate whether various extracellular calcium concentrations could modulate the expression of the tumor-associated antigen (TAA) recognized by monoclonal antibody (MAb) 44-3A6. It is highly expressed by the human lung adenocarcinoma cell line A549 and has been shown to be a 40-kD integral plasma membrane protein. Treatment of the A549 cell line with various concentrations of exogenous calcium showed a dose-dependent rise in the internal free calcium levels up to 2.4-2.9 mM (external calcium treatment). At higher concentrations, the internal calcium level showed a decline, indicating a higher calcium efflux. The calmodulin-dependent Ca(2+)-ATPase enzyme involved in calcium homeostasis was assayed under these same conditions. The enzyme activity increased with increasing external calcium concentrations showing a 5-fold increase in cells treated with 4.05 mM calcium. These data suggest that as the internal calcium approaches toxic levels, the Ca(2+)-regulated ATPase activity increases to reduce the calcium overload within the cell. Employing Western blot analysis and immunoperoxidase staining studies, this report shows that the antigen recognized by MAb 44-3A5 on A549 cells increased with an increase in calcium concentration. Evidence that this antigen is phosphorylated is presented using Western blot analysis of a radiolabeled antigen-enriched plasma membrane fraction. The previously reported subcellular localization, and now the phosphorylation and responsiveness to calcium by this TAA, gives it the properties predicted to be seen in a calcium 'pump-like' molecule. Thus, these studies support the hypothesis that this TAA may be important in intracellular calcium concentration control or that it is regulated via some calcium-mediated process.
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PMID:Changes in the expression of the tumor-associated antigen recognized by monoclonal antibody 44-3A6 in A549 cells due to calcium. 138 56

The hydrophobic, photoactivatable probe TID [3-trifluoromethyl-3-(m-[125I]iodophenyl)diazirine] was used to label the plasma membrane H(+)-ATPase from Saccharomyces cerevisiae. The H(+)-ATPase accounted for 43% of the total label associated with plasma membrane protein and incorporated 0.3 mol of [125I]TID per mol of 100 kDa polypeptide. The H(+)-ATPase was purified by octyl glucoside extraction and glycerol gradient centrifugation, and was cleaved by either cyanogen bromide digestion or limited tryptic proteolysis to isolate labeled fragments. Cyanogen bromide digestion resulted in numerous labeled fragments of mass less than 21 kDa. Seven fragments suitable for microsequence analysis were obtained by electrotransfer to poly(vinylidene difluoride) membranes. Five different regions of amino-acid sequence were identified, including fragments predicted to encompass both membrane-spanning and cytoplasmic protein structure domains. Most of the labeling of the cytoplasmic domain was concentrated in a region comprising amino acids 347 to 529. This catalytic region contains the site of phosphorylation and was previously suggested to be hydrophobic in character (Goffeau, A. and De Meis, L. (1990) J. Biol. 265, 15503-15505). Complementary labeling information was obtained from an analysis of limited tryptic fragments enriched for hydrophobic character. Six principal labeled fragments, of 29.6, 20.6, 16, 13.1, 11.4 and 9.7 kDa, were obtained. These fragments were found to comprise most of the putative transmembrane region and a portion of the cytoplasmic region that overlapped with the highly labeled active site-containing cyanogen bromide fragment. Overall, the extensive labeling of protein structure domains known to lie outside the bilayer suggests that [125I]TID labeling patterns cannot be unambiguously interpreted for the purpose of discerning membrane-embedded protein structure domains. It is proposed that caution should be applied in the interpretation of [125I]TID labeling patterns of the yeast plasma membrane H(+)-ATPase and that new and diverse approaches should be developed to provide a more definitive topology model.
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PMID:Assessing hydrophobic regions of the plasma membrane H(+)-ATPase from Saccharomyces cerevisiae. 139 Aug 24

The mediatophore is a presynaptic membrane protein that has been shown to translocate acetylcholine (ACh) under calcium stimulation when reconstituted into artificial membranes. The mediatophore subunit, a 15-kDa proteolipid, presents a very high sequence homology with the N,N'-dicyclohexylcarbodiimide (DCCD)-binding proteolipid subunit of the vacuolar-type H(+)-ATPase. This prompted us to study the effect of DCCD, a potent blocker of proton translocation, on calcium-dependent ACh release. The present work shows that DCCD has no effect on ACh translocation either from Torpedo synaptosomes or from proteoliposomes reconstituted with purified mediatophore. However, using [14C]DCCD, we were able to demonstrate that the drug does bind to the 15-kDa proteolipid subunit of the mediatophore. These results suggest that although the 15-kDa proteolipid subunits of the mediatophore and the vacuolar H(+)-ATPase may be identical, different domains of these proteins are involved in proton translocation and calcium-dependent ACh release and that the two proteins have a different membrane organization.
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PMID:Effect of N,N'-dicyclohexylcarbodiimide on acetylcholine release from Torpedo synaptosomes and proteoliposomes reconstituted with the proteolipid mediatophore. 140 80

The export of proOmpA, the precursor of outer membrane protein A from Escherichia coli, requires preprotein translocase, which is comprised of SecA, SecY/E, and acidic phospholipids. Previous studies of proOmpA translocation intermediates (Schiebel, E., Driessen, A. J. M., Hartl, F.-U., and Wickner, W. (1991) Cell 64, 927-939) suggested that the "slippage" of the translocating polypeptide chain and the high level of ATP hydrolysis, characteristic of the "translocation ATPase," were part of a futile cycle. To examine the role of the mature domain of proOmpA in its translocation-dependent ATP hydrolysis, we used chemical cleavage to generate NH2-terminal fragments of this preprotein. Each fragment contained the 21-residue leader region and either 53 or 228 residues of the mature domain (preproteins P74 and P249, respectively). As observed with full-length proOmpA, the translocation of each fragment requires ATP and both the SecA and SecY/E domains of translocase and is stimulated by the transmembrane proton electrochemical gradient. The apparent maximal velocities of P74 and proOmpA translocation are similar. While the translocation of P74 and of proOmpA show the same apparent Km for ATP, far less ATP is hydrolyzed during the translocation of P74. Thus, the mature carboxyl-terminal domain of proOmpA has a major role in supporting the translocation ATPase.
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PMID:The role of the mature domain of proOmpA in the translocation ATPase reaction. 146 25

The vacuolar ATPase of the yeast Saccharomyces cerevisiae acidifies the vacuolar lumen and generates an electrochemical gradient across the vacuole membrane. We have investigated the role of compartment acidification of the vacuolar system in the sorting of vacuolar proteins. Strains with chromosomal disruptions of genes (delta vat) encoding the A (69 x 10(3) M(r)), B (57 x 10(3) M(r)) or c (16 x 10(3) M(r)) subunits of the vacuolar ATPase accumulate and secrete precursor forms of the soluble vacuolar hydrolases carboxypeptidase Y and proteinase A. A kinetic analysis suggests that these precursor proteins accumulate in, and are secreted from, the Golgi complex or post-Golgi vesicles. In addition, subcellular fractionation shows that vacuolar hydrolase-invertase hybrid proteins are inefficiently localized to the vacuole in delta vat strains. This result suggests that the vat mutations cause a steady-state defect in vacuolar protein sorting. The vat mutations also affect the sorting of vacuolar membrane proteins. Precursor forms of alkaline phosphatase are accumulated in vat mutant cells, but to a lesser extent than is seen for the soluble vacuolar hydrolases. This finding, coupled with the insensitivity of alkaline phosphatase to the ATPase inhibitor bafilomycin A1, suggests that vacuolar membrane protein sorting is less sensitive to changes in lumenal pH when compared with the targeting of soluble vacuolar proteins. These results indicate that acidification of the vacuolar system is important for efficient sorting of soluble proteins to the vacuole.
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PMID:Mutations in the yeast vacuolar ATPase result in the mislocalization of vacuolar proteins. 149 Dec 35


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