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)

A manyfold increase in phosphorylation of cardiac sarcoplasmic reticulum (SR) was seen when SR was incubated in the presence of a bovine cardiac cyclic AMP-dependent protein kinase and cyclic AMP. This phosphoprotein had stability characteristics of a phosphoester in which the phosphate is incorporated largely into serine, and its formation did not required calcium ions, unlike the formation of acyl phosphoprotein intermediate of calcium-transport ATPase which is present within the same membrane. When examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the protein kinase-catalyzed phosphorylation occurred at a 22,000-dalton component of the cardiac sarcoplasmic reticulum. This 22,000-dalton protein has been named "phospholamban" (lambda alpha mu beta alpha nu epsilon iota nu = to receive), based on its ability to receive phosphate from ATP. Phosphorylation of phospholamban by cyclic AMP-dependent protein kinase was associated with the stimulation of calcium transport by the cardiac sarcoplasmic reticulum. This stimulation was accompanied by an increase in the calcium-activated ATPase activity, indicating that the overall rate of calcium transport rather than its efficiency is enhanced by protein kinase. The 22,000-dalton phopholamban was susceptible to trypsin. Brief digestion with trypsin in the presence of 1 M sucrose prevented subsequent phosphorylation of phospholamban, while leaving the calcium pump apparently intact. Incubation of trypsin-treated sarcoplasmic reticulum with cyclic AMP-depentent protein kinase did not result in the stimulation of calcium transport. These results may suggest that phospholamban is a modulator of the calcium pump of the cardiac sarcoplasmic reticulum.
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PMID:Regulation of calcium transport in cardiac sarcoplasmic reticulum by cyclic AMP-dependent protein kinase. 17 97

Cytochromes a, b and c, and their quantitative distribution in the cells, were studied by means of differential spectra in obligate methane oxidizing bacteria, Methylosinus trichosporium with the serine pathway of methane carbon assimilation and Methylomonas agile with the ribulose phosphate pathway of methane carbon assimilation, and different types of topography of intracytoplasmic membranes. The membranes are involved in processes of coupled respiration which was confirmed by cytochemical reactions employed for studying the terminal step of the electron transport chain and Mg2+-stimulated ATPase.
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PMID:[Localization of energy generators in methane oxidizing bacteria]. 18

Synthetic polypeptides were employed as substrates in kinetic analyses of the reaction mechanism for the catalytic subunit of a cyclic AMP-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) from calf thymus. This enzyme preparation was shown to catalyze the transfer of phosphate from ATP to histone H1 from calf thymus, as well as to two synthetic polypeptides, Arg-Lys-Ala-Ser-Gly-Pro (H1-6) and Arg-Arg-Lys-Ala-Ser-Gly-Pro (H1-7), corresponding to the amino acid sequence about serine-38 in calf H1. A related, basic heptapeptide corresponding to a sequence from pig liver pyruvate kinase, Leu-Arg-Arg-Ala-Ser-Leu-Gly (K), was also a substrate. The stoichiometry of peptide phosphorylation was established in each case as the transfer of 1 mol of phosphate from the gamma position of MgATP to the serine hydroxyl of 1 mol of the peptide. Steady-state, initial-velocity, kinetic parameters were determined for each substrate, using various concentrations of ATP. Under the conditions used, all synthetic peptides reacted with greater maximum velocities than whole histone H1. Nevertheless, the K(m) for H1, 54 muM, was lower than the K(m) values of the synthetic substrates. The most efficient substrate was peptide K, which had a V(max) of 50.6 mumol/min per mg of kinase and a K(m) of 63 muM. In the absence of peptide substrate no ATPase activity was detectable at a sensitivity of 0.05% of the rate of peptide phosphorylation, suggesting that ATP is not cleaved to form an unstable phosphoenzyme complex. The data are consistent with a sequential reaction mechanism involving a ternary complex between enzyme, polypeptide substrate, and ATP.
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PMID:Studies on the mechanism of phosphorylation of synthetic polypeptides by a calf thymus cyclic AMP-dependent protein kinase. 20 Sep 11

Thermoplasma acidophilum, a mycoplasma-like organism, grows optimally at 56 degrees C and pH2. The low temperature extreme of growth is 37 degrees C. The plasma membrane of cells grown at 37 degrees C was isolated and characterized physicobiochemically. Membrane lipids which comprise 25% of the membrane dry weight consist mainly of two repetitively methyl-branched C40 side chains that were ether-linked to two glycerol molecules. The lipid structures were elucidated by combined gas chromatography-mass spectroscopy, direct probe mass spectroscopy and 13C NMR. 37 degrees C-grown cells contained lipids with 42% more pentane cyclization than the 56 degrees C-grown cells. In 37 degrees C-grown cells, phospholipid and serine content decreased by about 10% each, carbohydrate content increased by 5%. EPR studies demonstrated an increase in membrane lipid fluidity of 37 degrees C-grown cells with an upper transition temperature at 35 degrees C which was shifted down by 10 degrees C compared with cells grown at 56 degrees C. Membrane-bound ATPase activities also indicated similar changes upon adaptation. There is a close correlation between membrane fluidity and physiological functioning of this membrane-bound enzyme.
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PMID:Structure of membrane lipids and physico-biochemical properties of the plasma membrane from Thermoplasma acidophilum, adapted to growth at 37 degrees C. 22 Oct 32

The molecular mechanisms involved in the inactivation of (Na+ + K+)-stimulated ATPase of Yoshida sarcoma cells by a cytotoxic protein (P6) from cobra venom have been examined. The overall data obtained using purified (Na+ + K+)-stimulated ATPase of Yoshida sarcoma cells suggest that cytotoxin P6 combines with phosphatidyl serine and a glycolipid which are closely associated with (Na+ + K+)-stimulated ATPase which in turn may lead to the inactivation of the enzyme in this cell system.
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PMID:Inactivation of membrane-bound (Na+ +K+)-ATPase of Yoshida sarcoma cells and cobra venom cytotoxin complex with the glycolipid components of the enzyme system. 22 83

The ATP-energy transducing system in membranes of Escherichia coli is inhibited by dicyclohexylcarbodiimide. The protein component of this complex with which carbodiimides covalently react to inhibit function was previously identified by labeling wild type and dicyclohexylcarbodiimide-resistant mutants with dicyclohexyl[14C]carbodiimide (Fillingame, R. H. (1975) J. Bacteriol. 124, 870-883). This specific carbodiimide-reactive protein has now been purified. The protein was extracted from the membrane with chloroform:methanol and chromatographed on DEAE-cellulose and hydroxypropyl Spehadex G-50 in this sulvent mixture. The resultant 700-fold purification yielded a protein that was homogeneous on dodecyl sulfate-acrylamide gel electrophoresis and virtually free of phospholipid. It remained soluble in neutral chloroform:methanol throughout the purification procedure. The amino acid composition of the purified protein was extraordinary in that only 16% of the amino acids present could be considered polar. Histidine, serine, cysteine, and tryptophan were not found. Abnormally high contents of methionine, glycine, alanine, and leucine were present. One mole of lysine and threonine were found/mole of dicyclohexyl[14C]carbodiimide bound. The minimum molecular weight based on the amino acid composition was 8400. The specific carbodiimide-reactive protein has also been purified without prior modification by dicyclohexylcarbodiimide. The unmodified protein eluted from DEAE-cellulose at a higher salt concentration than the dicyclohexylcarbodiimide-modified form, which suggested that the reaction with the carbodiimide neutralized the negative charge. Only one-third of the total carbodiimide-reactive protein in the membrane was modified by dicyclohexylcarbodiimide under conditions which maximally inhibited adenosine triphosphatase activity. These results rais the possibility that the carbodiimide-reactive protein may be present as an oligomer in the energy-transducing complex. The purification of the unmodified carbodiimide-reactive protein should permit assessment of tis biological function, particularly its role in the protein-translocation process that is catalyzed by this energy-transducing complex.
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PMID:Purification of the carbodiimide-reactive protein component of the ATP energy-transducing system of Escherichia coli. 78 71

We describe the effects of various cardioactive compounds on the Ca++ activation of force production and ATPase activity in isolated contractile structures from mammalian heart and, in some cases, skeletal muscle. We show that: 1) the Ca++ sensitizing activity of APP 201-533 does not discriminate between cardiac and skeletal muscle and is, therefore, not based on interaction with cardiac troponin I phosphorylation at serine 20. 2) compounds like trifluoperazine or bepridil, both known to interact with calmodulin, increase the Ca++ sensitivity of the contractile structures of the heart, in high concentrations, as expected from the high natural abundance of troponin C. 3) DPI 201-106 interacts with calmodulin (and presumably with the structurally closely related troponin C) in the microM concentration range. Its high Ca(++)-sensitizing potency in skinned cardiac muscle and a certain sensitivity of this effect to the detergent Triton X-100 suggest accumulation of the hydrophobic compound in the myofibrillar protein lattice.
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PMID:On the role of Ca++ binding proteins as possible targets for Ca++ sensitizing agents. 129 Mar 6

A Crithidia fasciculata 83-kDa protein purified during a separate study of C. fasciculata trypanothione synthetase was shown to have ATPase activity and to belong to the hsp90 family of stress proteins. Because no ATPase activity has previously been reported for the hsp90 class, ATP utilization by C. fasciculata hsp83 was characterized: this hsp83 has an ATPase kcat of 150 min-1 and a Km of 60 microM, whereas the homologous mammalian hsp90 binds ATP but has no ATPase activity. Crithidia fasciculata hsp83 undergoes autophosphorylation on serine and threonine at a rate constant of 3.3 x 10(-3) min-1. Similar analysis was performed on recombinant Trypanosoma cruzi hsp83, and comparable ATPase parameters were obtained (kcat = 100 min-1, Km = 80 microM, kautophosphorylation = 6.3 x 10(-3) min-1). The phosphoenzyme is neither on the ATPase hydrolytic pathway nor does it affect ATPase catalytic efficiency. Both C. fasciculata and T. cruzi hsp83 show up to fivefold stimulation of ATPase activity by peptides of 6-24 amino acids.
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PMID:83-kilodalton heat shock proteins of trypanosomes are potent peptide-stimulated ATPases. 130 85

The cardiac glycoside ouabain inhibits Na,K-ATPase by binding to the alpha subunit. In a highly ouabain resistant clone from the MDCK cell line, we have found two alleles of the alpha subunit in which the cysteine, present in the wild-type first transmembrane segment, is replaced by a tyrosine (Y) or a phenylalanine (F). We have studied the kinetics of ouabain inhibition by measuring the current generated by the Na,K-pump in Xenopus oocytes injected with wild-type and mutated alpha 1 and wild-type beta 1 subunit cRNAs. When these mutations, alpha 1C113Y and alpha 1C113F [according to the published sequence [Verrey et al. (1989) Am. J. Physiol., 256, F1034] were introduced in the alpha 1 subunit of the Na,K-ATPase from Xenopus laevis, the inhibition constant (Ki) of ouabain increased greater than 1000-fold compared with wild-type. A more conservative mutation, serine alpha 1C113S did not change the Ki. We observed that the decreased affinity for ouabain was mainly due to a faster dissociation, but probably also to a slower association. Thus we propose that an amino acid residue of the first transmembrane segment located deep in the plasma membrane participates in the structure and the function of the ouabain binding site.
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PMID:Mutation of a cysteine in the first transmembrane segment of Na,K-ATPase alpha subunit confers ouabain resistance. 131 69

A partial purification of the Epstein-Barr-virus nuclear antigen 2A (EBNA 2A) protein from the Epstein-Barr-virus-infected lymphoblastoid cell line, Cherry, has been designed. The main purification step was immunoaffinity chromatography, based on the mAb, 115E, directed towards the carboxy terminus of EBNA 2A. This was followed by chromatography over a Blue Sepharose column. According to silver-stained SDS/PAGE, EBNA 2A was estimated to be 20% pure. The purified fractions contained an ATPase activity that was inhibited by the mAb 115E. Immunopurification of six EBNA-2A-positive cell lines and their negative counterpart showed that only fractions from EBNA-2A-positive lines contained ATPase activity. In gel-filtration experiments EBNA 2A eluted as a 75-kDa protein in conjunction with an ATPase activity. The EBNA 2A protein was covalently labeled by the ATP analog [14C]5'-[p-(fluorosulfonyl)benzoyl]adenosine. The ATPase activity was found to be optimal in the presence of 0.25 mM MgCl2 or CaCl2, whereas, in the presence of MnCl2 and ZnCl2, the activity was only about 50% of the control. High concentrations of Na2VO3 and heparin do not interfere with the activity, while 2.5 mM NaF or 0.5 M NaCl give a 50% reduction of the activity. The Km for ATP and for GTP was 13 microM and 11 microM, respectively, and the Vmax for ATP was about six-times higher than with GTP as substrate. Other low-molecular-mass non-protein phosphate esters, such as phosphoserine or phosphothreonine inhibited the ATPase activity with a Ki of 18 and 32 microM, respectively. Phosphotyrosine had a Ki of 480 microM. Serine, threonine and tyrosine had no inhibitory effect on the ATPase activity.
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PMID:Biochemical characterization of Epstein-Barr virus nuclear antigen 2A and an associated ATPase activity. 132 Oct 48


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