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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The soluble form of mitochondrial adenosine triphosphatase was purified in an electrophoretically and immunologically pure form from sweet potato root tissue. The enzyme consisted of six kinds of subunits with different molecular weights (52,500, 51,500, 35,500, 26,000, 23,000, and 12,000), and its molecular weight was about 370,000. Adenosine triphosphatase associated with the submitochondrial particles was oligomycin-sensitive and heat-labile, whereas the soluble form of the enzyme was oligomycin-insensitive and cold-labile. The enzyme in either the membrane-bound or the soluble form showed negative cooperativity. Both experiments with polyacrylamide gel electrophoresis and immunological methods suggest that some of the subunits, probably those with molecular weights of 52,500 and 51,500, are dissociated from the enzyme protein during storage of the enzyme preparations.
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PMID:Purification and characterization of the soluble form of mitochondrial adenosine triphosphatase from sweet potato. 622 90

Electron spin resonance, enzymatic, and SDS-polyacrylamide gel electrophoretic investigations of erythrocyte membranes from patients with Alzheimer's disease were performed. Alterations in the physical state of membrane proteins in Alzheimer's disease erythrocytes were found by spin labeling studies. However, no alterations in membrane lipid fluidity or in the activities of membrane-bound sodium plus potassium-stimulated, magnesium-dependent adenosine triphosphatase or acetylcholinesterase could be demonstrated. Also, no changes in staining profiles of AD erythrocyte membrane proteins subjected to electrophoresis were observed. The altered conformation and/or organization of extraneural membrane proteins in Alzheimer's disease suggests the possibility that this disorder may have more widespread membrane involvement than was originally thought.
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PMID:Spin label and biochemical studies of erythrocyte membranes in Alzheimer's disease. 624 87

Sodium and potassium ion-activated adenosine triphosphatase is known to be composed of at least two different polypeptides, alpha and beta. When a detergent-treated supernatant preparation of the enzyme is reacted with the cross-linking reagent, cupric phenanthroline, a single, covalent heterodimer is formed. This product is formed from one of each of the two polypeptides. The remaining, unreacted alpha and beta chains maintain a constant ratio to each other throughout the reaction. The same heterodimer is formed in membrane-bound enzyme when reacted with several other cross-linking reagents. The protein mass ratio between the chains in the native enzyme, determined by two methods, is 2.15 +/- 0.16. Using this value and a value of 121,000 +/- 6,000 for the molecular weight of the larger polypeptide, a molecular weight of 56,000 +/- 7,000 can be calculated for the protein portion of the smaller polypeptide. Upon removal of a substantial portion of the carbohydrate from the smaller polypeptide, a change in its electrophoretic mobility is observed, while that of the larger polypeptide remains unaffected. The apparent length of this unglycosylated small chain is 450 residues, corresponding to a molecular weight of 51,000. Taken together, these results demonstrated that the two polypeptides of the (Na+ + K+)-ATPase exist in an equimolar, noncovalent association in the native enzyme, and that the protein molecular weight of the minimum asymmetric unit is 177,000 +/- 13,000, Previous results which address the question of the quaternary structure of the ATPase are re-examined in light of these determinations.
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PMID:Stoichiometry and molecular weight of the minimum asymmetric unit of canine renal sodium and potassium ion-activated adenosine triphosphatase. 624 16

Previous studies in our laboratory had demonstrated alterations in the physical state of membrane proteins in erythrocytes in Huntington's disease. In order to assess the specificity of our findings, the results of electron spin resonance studies of protein and lipid components, scanning electron-microscopic studies, enzymatic analyses of membrane-bound sodium plus potassium stimulated, magnesium-dependent adenosine triphosphatase and protein kinase, and cell deformability studies of erythrocyte membranes have been performed in the neurological disorders, Huntington's disease, Friedreich's ataxia, Alzheimer's disease, amyotrophic lateral sclerosis, and myotonic and Duchenne muscular dystrophy. Comparison of the results revealed that alterations in the biophysical and biochemical states of erythrocyte membranes in each disorder are specific to the particular disease state with the exception of those in Friedreich's ataxia and Alzheimer's disease. In the latter instance, the clinical and pathological alterations suggest that these two diseases have different primary defects. Our studies suggest that the molecular basis of each disease is different. In addition, the results suggest that biophysical and biochemical investigations of extraneural tissue in Huntington's disease and other neurological disordes have the potential of clarifying the molecular mechanisms by which these diseases arise.
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PMID:Specificity of biophysical and biochemical alterations in erythrocyte membranes in neurological disorders--Huntington's disease, Friedreich's ataxia, Alzheimer's disease, amyotrophic lateral sclerosis, and myotonic and duchenne muscular dystrophy. 625 Nov 75

Preparations of isolated brush border plasma membrane of Hymenolepis diminuta and H. microstoma possess the following enzymatic activities: alkaline phosphohydrolase (E.C. 3.1.3.1); Type I phosphodiesterase (E.E. 3.1.4.1); ribonuclease (E.C. 3.1.4.22); adenosine triphosphatase (E.C. 3.6.1.3); and 5'-nucleotidase (E.C. 3.1.3.5). The following enzymatic activities could not be demonstrated in either membrane preparation: Type II phosphodiesterase (E.C. 3.1.4.18); cyclic adenosine-3', 5'-monophosphate phosphodiesterase (E.C. 3.1.4.17); leucine aminopeptidase (E.C. 3.4.11.1); maltase (alpha-glucosidase; E.C. 3.2.1.20); and lactase (beta-galactosidase; E.C. 3.2.1.23). These data generally agree with those of previous studies in which similar membrane-bound enzymes were demonstrated in intact (living) worms.
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PMID:A comparison of membrane-bound enzymes of the isolated brush border plasma membranes of the cestodes of Hymenolepis diminuta and H. microstoma. 628 Jan 22

Adenosine triphosphatase activity of U. urealyticum is an integral membrane-bound protein which cannot be detached from the membrane by mild treatment with EDTA in low-ionic strength media nor by ionic detergents which rapidly inactivated the enzyme. The enzyme was Mg++ dependent; Mn++ and Co++ could replace Mg++ to some extent. A slight stimulatory effect was also exerted by sodium and lithium. The enzyme showed a nucleotide triphosphatase activity, but ADP was hydrolyzed at close to 40% the rate of ATP and other nucleotide monophosphatase were hydrolyzed at a very slow rate. Oubain and oligomycin did not inhibit the adenosine triphosphatase activity, whereas DCCD, NBD-Cl and several sulfhydryl-blocking reagents strongly reduced its activity. The enzyme could not be stimulated by trypsin pretreatment. It seems that the complex enzyme is tightly linked to the lipid bilayer of the membrane and differs in many aspects from the F0-F1 (Mg++, Ca++)-ATPase of bacteria.
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PMID:Adenosine triphosphatase activity of Ureaplasma urealyticum. 628 75

The existence of conformers of the sodium- and potassium-dependent adenosine triphosphatase has been known for some time, yet their structures remain poorly characterized. In this study, circular dichroism spectroscopy was utilized to assess the secondary structural composition of the enzyme, particularly with regard to the E1 and E2 states that are associated with the presence of Na+ and K+, respectively. Parallel experiments were performed in which highly purified Na/K-ATPase from guinea pig kidney outer medulla was incubated with various cations and then examined by CD. The spectra were corrected for optical effects which arise due to the particulate nature of the membrane-bound protein, and then fit to reference data derived from a set of proteins with known secondary structures. In the peptide backbone region of the spectrum (190-240 nm), significant differences between the E1 and E2 conformers were detected and quantified in terms of the proportions of secondary structures present. An extensive conformational change rather than a small local perturbation must be responsible for the differences observed.
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PMID:Secondary structural composition of the Na/K-ATPase E1 and E2 conformers. 632 76

Light- and electron-microscopic histochemical procedures were used to show the distribution of the membrane-bound enzymes alkaline phosphatase (Alp), adenosine triphosphatase (ATPase), and 5'-nucleotidase (5'-nuc) in the livers of lamprey, Petromyzon marinus, throughout the life cycle. In larvae, the three enzymes are located at the biliary pole on the canalicular membranes of microvilli. At metamorphosis the enzymes become localized at all lateral cell surfaces of hepatocytes as bile canaliculi degenerate in the programmed regression of the entire biliary tree. This latter pattern of enzyme distribution persists during the parasitic adult phase but no activity is evident in individuals in the spawning migration. As the timing of the relocalization of enzymatic activity correlates well with a build-up of bile products and iron during metamorphosis, it is suggested that the lateral surface may be the new site for transport of these products.
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PMID:Relocalization of membrane enzymes accompanies biliary atresia in lamprey liver. 632 18

Vanadyl, the tetravalent state of vanadium and a divalent cation, VO2+, was a relatively powerful inhibitor of highly purified membrane-bound sodium and potassium ion transport adenosine triphosphatase. The sensitivity of the ATPase activity to vanadyl characteristically correlated positively with the specific activity of the enzyme preparation. Inhibition ranged from nearly complete inhibition at less than 5 microM vanadyl for some of the purest fractions (specific activity approximately 45 mumol/min/mg of protein) to no observable inhibition at 300 microM vanadyl in one crude preparation of the enzyme with a specific activity of 10 mumol/min/mg of protein. The level of free vanadyl was reduced by incubation with these membranes, but this reduction was not sufficient to account for the low sensitivity to vanadyl observed in crude preparations. A reduction in specific activity by partial inactivation of a sensitive preparation by treatment with FeCl3 and ascorbate reduced its sensitivity to vanadyl. Anionic ligands of the enzyme, vanadate or ATP, increased the rate of recovery from inhibition after chelation of free vanadyl. At pH 6.1, the inhibition was characteristically fully reversible (t1/2 approximately 10 min), whereas at pH 8.1 it was stable for hours. The degree and stability of enzyme inhibition by vanadyl increased for several hours during incubation of the vanadyl-enzyme mixture, and at pH 6.1 the properties of the inhibitor itself also changed with time. Preincubation of the ion at that pH for 5 h before addition of the enzyme produced a more stable inhibition. The time- and pH-dependent changes in the degree and stability of enzyme inhibition probably relate to the complex chemistry of the vanadyl ion in solution.
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PMID:Inhibition of (Na,K)-ATPase by tetravalent vanadium. 632 13

Tight divalent metal binding sites in the beef heart mitochondrial adenosine triphosphatase were studied using the procedure of reconstitution of soluble F1 with F1-depleted membranes (SU particles). Soluble F1 has been shown previously to contain two tight-binding site for Mg. Both of these sites were present on membrane-bound enzyme. Co and Mn, substituted at the second of the two Mg-binding sites on soluble F1, became incorporated with F1 into membrane-bound enzyme. Use of radioactive Co and Mn showed that they behaved differently during short bursts of succinate oxidation or ATP hydrolysis. Co remained stably bound, whereas Mn was released to the extent of 55-80%. The results extend previous work to show that the membrane proton-ATPase is an Mg-metalloenzyme containing a structural Mg site and a second Mg site possibly involved in catalysis. The conversion of 2-Mg F1 to 1-Mg F1 during purification and storage is shown to be due to use of ammonium sulfate precipitation, and the dependence of reuptake of Mg (1-Mg F1 leads to 2-Mg F1) on nucleotides is described.
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PMID:Divalent metals in beef heart mitochondrial adenosine triphosphatase. Demonstration of the metals in membrane-bound enzyme and studies of the interconversion of the "1-Mg" and "2-Mg" forms of the enzyme. 645 21


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