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)

Na+, K+-ATPase is a heterodimeric enzyme responsible for the active maintenance of sodium and potassium gradients across the plasma membrane. Recently, cDNAs for several tissue-specific isoforms of the larger catalytic alpha-subunit and the smaller beta-subunit have been cloned. We have hybridized rat brain and human kidney cDNA probes, as well as human genomic isoform-specific DNA fragments, to Southern filters containing panels of rodent X human somatic cell hybrid lines. The results obtained have allowed us to assign the loci for the ubiquitously expressed alpha-chain (ATP1A1) to human chromosome 1, region 1p21----cen, and for the alpha 2 isoform that predominates in neural and muscle tissues (ATP1A2) to chromosome 1, region cen----q32. A common PstI RFLP was detected with the ATP1A2 probe. The alpha 3 gene, which is expressed primarily in neural tissues (ATP1A3), was assigned to human chromosome 19. A fourth alpha gene of unknown function (alpha D) that was isolated by molecular cloning (ATP1AL1) was mapped to chromosome 13. Although evidence to date had suggested a single gene for the beta-subunit, we found hybridizing restriction fragments derived from two different human chromosomes. On the basis of knowledge of conserved linkage groups on human and murine chromosomes, we propose that the coding gene ATP 1B is located on the long arm of human chromosome 1 and that the sequence on human chromosome 4 (ATP 1BL1) is either a related gene or a pseudogene.
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PMID:Chromosomal localization of human Na+, K+-ATPase alpha- and beta-subunit genes. 284 49

Chromaffin granule membranes were incubated in the presence of low ATP concentrations, at low temperature. A phosphorylated compound was rapidly formed which was stable in 10% trichloroacetic acid at 0 degree C. The lability of this compound in the presence of hydroxylamine or hot trichloroacetic acid indicated an acylphosphate, i.e., an ATPase phosphointermediate. Vanadate but not N-ethylmaleimide inhibited the formation of this derivative. Since the ATP-dependent generation of a transmembrane potential in chromaffin granule vesicles by the H+-pump was inhibited by N-ethylmaleimide but not by vanadate, the acylphosphate should not be associated with the H+-pump, i.e. ATPase I. We suggest that it is associated with ATPase II, an ATPase of unknown function present in chromaffin granule membrane preparations. This hypothesis is supported by the fact that ATPase II is vanadate sensitive and has a molecular mass of 140 kDa, properties similar to those of the phosphorylated intermediate.
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PMID:The acylphosphate present in chromaffin granule membrane preparations is not associated with the proton-pump. 287 89

The unc (or atp) operon of Escherichia coli comprises eight genes encoding the known subunits of the proton-translocating ATP synthase (H+-ATPase) plus a ninth gene (uncI) of unknown function. The subunit stoichiometry of the H+-ATPase (alpha 3 beta 3 gamma 1 delta 1 epsilon 1 a1b2c10-15) requires that the respective unc genes be expressed at different rates. This review discusses the experimental methods applied to determining how differential synthesis is achieved, and evaluates the results obtained. It has been found that the primary level of control is translational initiation. The translational efficiencies of the unc genes are determined by primary and secondary mRNA structures within their respective translational initiation regions. The respective rates of translation are matched to the subunit requirements of H+-ATPase assembly. Finally, points of uncertainty remain and experimental strategies which will be important in future work are discussed.
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PMID:Expression of the unc genes in Escherichia coli. 289 71

Enhanced fluorescence of the ATP analogue 2',3'-O-(2,4,6-trinitrocyclohexyldienylidine)adenosine 5'-triphosphate (TNP-ATP), bound to the Ca2+-ATPase of skeletal muscle sarcoplasmic reticulum, is closely related to phosphoenzyme levels (Bishop, J. E., Johnson, J. D., and Berman, M. C. (1984) J. Biol. Chem. 259, 15163-15171) and has an emission maximum consistent with decreased polarity of the TNP-ATP-binding site. The phosphoenzyme conformation responsible for increased nucleotide-binding site hydrophobicity has been studied by redistribution of phosphoenzyme intermediates following specific thiol group modification. N-Ethylmaleimide, in the presence of 50 microM Ca2+, 1 mM adenyl-5'-yl imidodiphosphate, pH 7.0, at 25 degrees C for 30 min, selectively modified the SH group essential for phosphoenzyme decomposition, which resulted in decreased ATPase activity, Ca2+ uptake, and a decrease in ATP-induced TNP-ATP fluorescence. Phosphorylated (Ca2+, Mg2+)-ATPase levels from [gamma-32P] ATP remained relatively unaffected (3.1 nmol/mg), but the ADP-insensitive fraction decreased from 56 to 15%. Phosphoenzyme levels from 32Pi were also decreased to the same extent as turnover, with equivalent loss of Pi-induced TNP-ATP fluorescence. The E1 to E2 transition, as monitored by the change in intrinsic tryptophan fluorescence, was unaffected. Modification of thiol groups of unknown function did not modify turnover-induced TNP-ATP fluorescence. It is concluded that the ADP-insensitive phosphoenzyme, E2-P, is responsible for enhanced TNP-ATP fluorescence. This suggests that the conformational transition, 2Ca2+outE1 approximately P----2Ca2+inE2-P, is associated with altered properties of the noncatalytic, or regulatory, nucleotide-binding site.
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PMID:Phosphoenzyme conformational states and nucleotide-binding site hydrophobicity following thiol modification of the Ca2+-ATPase of sarcoplasmic reticulum from skeletal muscle. 295 14

A plasma membrane-enriched fraction from rat myometrium shows ATP-Mg2+-dependent active calcium uptake which is independent of the presence of oxalate and is abolished by the Ca2+ ionophore A23187. Ca2+ loaded into vesicles via the ATP-dependent Ca2+ uptake was released by extravesicular Na+. This showed that the Na+/Ca2+ exchange and the Ca2+ uptake were both occurring in plasma membrane vesicles. In a medium containing KCl, vanadate readily inhibited the Ca2+ uptake (K1/2 5 microM); when sucrose replaced KCl, 400 microM-vanadate was required for half inhibition. Only a slight stimulation of the calcium pump by calmodulin was observed in untreated membrane vesicles. Extraction of endogenous calmodulin from the membranes by EGTA decreased the activity and Ca2+ affinity of the calcium pump; both activity and affinity were fully restored by adding back calmodulin or by limited proteolysis. A monoclonal antibody (JA3) directed against the human erythrocyte Ca2+ pump reacted with the 140 kDa Ca2+-pump protein of the myometrial plasma membrane. The Ca2+-ATPase activity of these membranes is not specific for ATP, and is not inhibited by mercurial agents, whereas Ca2+ uptake has the opposite properties. Ca2+-ATPase activity is also over 100 times that of calcium transport; it appears that the ATPase responsible for transport is largely masked by the presence of another Ca2+-ATPase of unknown function. Measurements of total Ca2+-ATPase activity are, therefore, probably not directly relevant to the question of intracellular Ca2+ control.
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PMID:Characteristics of the Ca2+ pump and Ca2+-ATPase in the plasma membrane of rat myometrium. 297 50

Sodium plus potassium activated adenosinetriphosphatase [(Na,K)ATPase] is composed of a catalytic subunit (alpha) and a glycoprotein subunit (beta) of unknown function. A method has been developed to label the beta subunit of purified dog kidney (Na,K)ATPase with fluorescent probes. The method consists of oxidation of beta-subunit oligosaccharides, reaction of the resulting aldehydes with fluorescent hydrazides, and reduction of the hydrazones and unreacted aldehydes with NaBH4. Two oxidation methods were compared. Simultaneous treatment with neuraminidase and galactose oxidase did not inhibit significantly (Na,K)ATPase activity and allowed insertion of up to 11 mol of probe per mol of beta. In contrast, oxidation of (Na,K)ATPase oligosaccharides with periodate resulted in 50-80% inhibition of the (Na,K)ATPase activity with low or undetectable labeling. Eleven commercial probes and two novel hydrazides were tested for labeling of (Na,K)ATPase treated with galactose oxidase and neuraminidase. Eight probes did not label (Na,-K)ATPase but labeled red cell ghosts oxidized with periodate. Four probes labeled beta specifically but either adsorbed to the membrane tightly, or cross-linked the beta subunits, or formed unstable adducts. Lucifer yellow CH labeled beta specifically without membrane adsorption. Labeling stoichiometries from 1 to 11 mol of lucifer yellow CH per mol of beta were obtained without inhibition of (Na,K)ATPase activity and without significant alteration of the anthroylouabain binding capacity or its association and dissociation kinetics. Anthroylouabain specifically bound to the lucifer-labeled (Na,K)ATPase had a decreased quantum yield, probably due to resonance energy transfer. This suggests that the sites of lucifer attachment on beta are within energy transfer distance from the cardiac glycoside site on alpha.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Labeling of the glycoprotein subunit of (Na,K)ATPase with fluorescent probes. 298 55

The sodium/potassium-dependent ATPase [(Na+ + K+)ATPase], which establishes and maintains the Na+ and K+ gradients across the plasma membrane of animal cells, consists of two subunits, alpha and beta. Complementary DNA clones encoding the catalytic (alpha) subunit of sheep kidney and Torpedo californica electroplax enzymes have previously been isolated and characterized. However, there is little information concerning the primary structure of the beta-subunit, a glycoprotein of unknown function and relative molecular mass (Mr) approximately 55,000 (ref. 3). Here we describe the isolation and characterization of a cDNA clone containing the entire coding region of the beta-subunit of the sheep kidney (Na+ + K+)ATPase. We also discuss structural aspects of the protein and present evidence for a possible evolutionary relationship with the KdpC subunit of the Escherichia coli K+-ATPase.
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PMID:Amino-acid sequence of the beta-subunit of the (Na+ + K+)ATPase deduced from a cDNA. 301 56

(Na,K)-ATPase, the enzyme responsible for active transport of Na and K across the plasma membranes of animal cells, consists of a catalytic subunit (alpha) and a glycoprotein subunit (beta) with unknown function. We have determined the distance between fluorescent probes directed to specific sites on the alpha- and beta-subunits and ligand-induced changes in the fluorescence of a probe specifically attached to the beta-subunit. The cardiac glycoside site on the alpha-subunit was labeled with anthroylouabain [Fortes, P. A. G. (1977) Biochemistry 16, 531-540]. The oligosaccharides on the beta-subunit were labeled with lucifer yellow carbohydrazide [Lee, J. A., & Fortes, P. A. G. (1985) Biochemistry 24, 322-330]. Resonance energy transfer from anthroylouabain to lucifer yellow was measured by steady-state and time-resolved fluorescence spectroscopy. The distance between these probes was determined from the efficiency of energy transfer. The average distance between anthroylouabain and lucifer yellow was 47 A and was independent of the number of acceptor molecules attached to the beta-subunit. The measured distance corresponds to the distance between the cardiac glycoside site and the center of the labeled oligosaccharides on the beta-subunit within one alpha beta dimer. The distance was the same (47 A) when anthroylouabain was bound with ATP or Pi as phosphorylating ligands but increased to 49 A in the presence of vanadate. The change in average distance provides quantitative evidence of a conformational difference between the complexes of cardiac glycosides with (Na,K)-ATPase induced by phosphorylating ligands or by vanadate.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Spatial relationship and conformational changes between the cardiac glycoside site and beta-subunit oligosaccharides in sodium plus potassium activated adenosinetriphosphatase. 302 71

We have investigated the localization of a set of intrinsic ATPase activities associated with purified synaptic plasma membranes and consisting of (a) a Mg2+-ATPase; (b) an ATPase active at high concentrations of Ca2+ in the absence of Mg2+ (CaH-ATPase); (c) a Ca2+ requiring Mg2+-dependent ATPase (Ca + Mg)-ATPase, stimulated by calmodulin (Ca-CaM-ATPase); (d) a Ca2+-dependent ATPase stimulated by dopamine (DA-ATPase); and (e) the ouabain-sensitive (Na + K)-ATPase. The following results were obtained: (1) All ATPases are largely confined to the presynaptic membrane; (2) the DA-, (Ca + Mg)-, (Ca-CaM)-, and (Na + K)-ATPases are oriented with their ATP hydrolysis sites facing the synaptoplasm; (3) the Mg- and CaH-ATPases are oriented with their ATP hydrolysis sites on the junctional side of the presynaptic membrane and are therefore classified as ecto-ATPases of as yet unknown function.
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PMID:Localization of endogenous ATPases at the nerve terminal. 629 99

A vesicular fraction isolated from bovine aorta and enriched in fragmented sarcoplasmic reticulum (FSR) exhibited active calcium transport and ATPase activity. By use of a hypotonic NaHCO3 extraction solution, an active preparation was isolated that retained activity for up to 4 days. A small but significant (P less than 0.05) Ca2+-stimulated, Mg2+-dependent ATPase associated with calcium transport was demonstrated with a specific activity of 0.33 mumol inorganic phosphate (Pi).mg-1.min-1. The basal Mg2+ ATPase demonstrated Michaelis-Menten kinetics [Km(Mg2+-ATP) = 0.44 +/- 0.01 X 10(-3) M; Vmax = 2.22 +/- 0.01 mumolPi.mg-1.min-1]. The Ca2+-stimulated, Mg2+-ATPase demonstrated apparent substrate inhibition (Ks approximately 10 mM) with no evidence for end-product (ADP) or excess added Ca2+ contributing to this inhibition. Oxalate-supported active calcium uptake velocities also exhibited quantitatively similar substrate inhibition. These results suggest that FSR from vascular smooth muscle contains either two enzymes or one enzyme with two isomeric forms, one of which is associated with the calcium uptake activity of this structure and the other of unknown function.
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PMID:Influence of ATP on sarcoplasmic reticulum function of vascular smooth muscle. 646 Dec 58


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