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)

We examined the effect of cGMP on Na+/Ca2+ exchange in rat aortic smooth muscle cells (VSMCs) in primary culture. The intracellular Ca2+ concentration [( Ca2+]i) was raised by adding ionomycin to VSMCs incubated at high extracellular pH (pH0) (pH0 = 8.8) and high extracellular Mg2+ (Mg2+0) (Mg2+0 = 20 mM), conditions that inhibit activity of the sarcolemmal Ca2+ pump. 45Ca2+ efflux observed under these conditions was mostly extracellular Na+ (Na+0)-dependent and thus presumably catalyzed by the Na+/Ca2+ exchanger. Brief treatment of VSMCs with 8-bromo-cGMP or atrial natriuretic peptide increased this Na+0-dependent 45Ca2+ efflux by about 50%. The 8-bromo-cGMP treatment did not significantly influence total cell Na+, membrane potential, and cell pH. Conversely, when VSMCs were loaded with Na+ and then exposed to a Na+0-free medium, the rate of 45Ca2+ uptake into VSMCs increased as cell Na+ increased. Prior treatment of VSMCs with 8-bromo-cGMP accelerated 45Ca2+ uptake by up to 60% without influencing Na+ loading itself. Treatment of VSMCs with 25 microM 2,5-di-(tert-butyl)-1,4-benzohydroquinone, an inhibitor of the sarcoplasmic reticulum Ca(2+)-ATPase, induced a transient elevation of [Ca2+]i. 8-Bromo-cGMP stimulated the rate of recovery phase of this Ca2+ transient measured in the high pHo/high Mg2+o medium. All these results indicate that cGMP stimulates Na+/Ca2+ exchange in VSMCs.
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PMID:Cyclic GMP stimulates Na+/Ca2+ exchange in vascular smooth muscle cells in primary culture. 164 93

Organotin compounds have been shown to interfere with cardiovascular system. We have studied the in vitro and in vivo effects of tributyltin bromide (TBT), triethyltin bromide (TET) and trimethyltin chloride (TMT) on the cardiac SR Ca2+ pump, as well as on protein phosphorylation of SR proteins, in order to understand the relative potency of these tin compounds. All the three tin compounds inhibited cardiac SR 45Ca uptake and Ca(2+)-ATPase in vitro in a concentration-dependent manner. The order of potency for Ca(2+)-ATPase as determined by IC50, is TBT (2 microM) greater than TET (63 microM) greater than TMT (280 microM). For 45Ca uptake, it followed the same order i.e., TBT (0.35 microM) greater than TET (10 microM) greater than TMT (440 microM). In agreement with the in vitro results, both SR Ca(2+)-ATPase and 45Ca uptake were significantly inhibited in rats treated with these tin compounds, indicating that these tin compounds inhibit cardiac SR Ca2+ transport. cAMP significantly elevated (70-80%) the 32P-binding to SR proteins in vitro in the absence of any organotin. In the presence of organotins, cAMP-stimulated 32P-binding to proteins was significantly reduced, but the decrease was concentration dependent only at lower concentrations. The order of potency is TBT greater than TET greater than TMT. In agreement with in vitro studies, cAMP-dependent 32P bound to proteins was significantly reduced in rats treated with TBT, TET and TMT. SDS-polyacrylamide gel electrophoresis of the cardiac SR revealed at least 30 Coomassie blue stainable bands ranging from 9 to 120 kDa.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inhibition of Ca2+ transport associated with cAMP-dependent protein phosphorylation in rat cardiac sarcoplasmic reticulum by triorganotins. 165 51

Triorganotins have been reported to affect heme metabolism as well as the cardiovascular system. Our recent studies indicated that these organotins inhibit cardiac sarcoplasmic reticulum Ca(2+)-transport and cAMP-stimulated phosphorylation of specific proteins involved in Ca2+ transport, suggesting their interference with cardiac adrenergic function. The present study determines the effect of three organotins--tributyltin bromide (TBT), triethyltin bromide (TET) and trimethyltin chloride (TMT)--on rat cardiac ATPases and catecholamine binding, since these phenomena are involved in cardiac function. Cardiac membrane fraction was prepared from heart ventricles of male Sprague-Dawley rats. All three organotins inhibited cardiac Na+,K(+)-ATPase, [3H]ouabain binding, K(+)-activated p-nitrophenyl phosphatase (K(+)-PNPPase) and oligomycin-sensitive (OS) and oligomycin-insensitive (OI) Mg(2+)-ATPase in a concentration-dependent manner. K(+)-PNPPase was less sensitive to these triorganotins when compared to Na+K(+)-ATPase, suggesting that triorganotins affect the Na(+)-pump activity by acting on the Na(+)-dependent phosphorylation process. OS Mg(2+)-ATPase was more sensitive to these organotins when compared to OI Mg(2+)-ATPase, confirming their potent effect on the enzymes of oxidative phosphorylation. The order of potency is TBT greater than TET greater than TMT. TET and TMT, but not TBT, inhibited [3H]norepinephrine and [3H]dopamine binding to cardiac membranes in a concentration-dependent manner, the effect being more with TET. These results suggest that triorganotins inhibit sodium pump activity as well as ATP synthesis. Since Na+,K(+)-ATPase is involved in the active transport of catecholamines, triorganotins not only inhibited the catecholamine transport but also to some extent affected catecholamine binding, thus interfering with cardiac function.
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PMID:Triorganotin inhibition of rat cardiac adenosine triphosphatases and catecholamine binding. 166 43

The uptakes of gamma-aminobutyrate (GABA) and L-glutamate into synaptic vesicles isolated from rat brain were compared with respect to the effects of 4-acetamido-4'-isothiocyanostilbene-2,2'- disulphonic acid (SITS), 4,4'-di-isothiocyanostilbene-2,2'-disulphonic acid (DIDS) and 5-nitro-2-(3-phenylpropylamino)benzoic acid (N144), agents known to block anion channels. The uptake of glutamate was inhibited by low micromolar concentrations of SITS, DIDS and N144. GABA uptake was much less sensitive to these agents than was glutamate uptake. SITS and N144 inhibited the vacuolar H(+)-ATPase of synaptic vesicles to a smaller extent than the glutamate uptake. The uptake of GABA was not affected by the permeant anions Cl- and Br-, whereas the uptake of glutamate was highly stimulated by low concentrations of these ions. The uptakes of both glutamate and GABA were inhibited by similar, but not identical, concentrations of the lipophilic anion SCN-.
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PMID:Transport of gamma-aminobutyrate and L-glutamate into synaptic vesicles. Effect of different inhibitors on the vesicular uptake of neurotransmitters and on the Mg2(+)-ATPase. 167 66

Detergent-solubilization of hog gastric microsomal membrane proteins followed by affinity chromatography using wheat germ agglutinin or Ricinus communis I agglutinin resulted in the isolation of five glycoproteins with the apparent molecular masses on sodium dodecyl sulfate polyacrylamide gels of (in kDa): 60-80 (two glycoproteins sharing this molecular mass); 125-150; and 190-210. In the nonionic detergent Nonidet P-40 (NP-40), the 94 kDa H+/K(+)-ATPase was recovered exclusively in the lectin-binding fraction; however, in the cationic detergent dodecyltrimethylammonium bromide, most of the ATPase was recovered in the nonbinding fraction. Detection of glycoproteins either by periodic acid-dansyl hydrazine staining of carbohydrate in polyacrylamide gels or by Western blots probed with lectins indicated that the majority of the ATPase molecules are not glycosylated. In addition, in the absence of microsomal glycoproteins, the NP-40-solubilized ATPase does not bind to a lectin column. Taken together, these results suggest that the recovery of NP-40-solubilized ATPase in the lectin-binding fraction is due to its noncovalent interaction with a gastric microsomal glycoprotein. Immunoprecipitation of the ATPase from NP-40-solubilized microsomal membrane proteins resulted in the co-precipitation of a single 60-80 kDa glycoprotein. Characterization of the 60-80 kDa glycoprotein associated with the ATPase revealed that: it is a transmembrane protein; it has an apparent core molecular mass of 32 kDa; and, it has five asparagine-linked oligosaccharide chains. Given its similarity to the glycosylated beta-subunit of the Na+/K(+)-ATPase, this 60-80 kDa gastric microsomal glycoprotein is suggested to be a beta-subunit of the H+/K(+)-ATPase.
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PMID:Isolation and characterization of gastric microsomal glycoproteins. Evidence for a glycosylated beta-subunit of the H+/K(+)-ATPase. 169 26

We prepared proton-transporting membrane vesicles from the avian osteoclast's ruffled membrane, a specialized region of the cell surface that acidifies the bone resorption space. We demonstrated a unique conductive Cl- permeability that is charge coupled to the vesicle H(+)-ATPase and is required for acidification. Ion replacement indicated an anion selectivity of Br- approximately Cl- greater than SO4(2-) greater than NO3- approximately SCN- in supporting acidification. The anion channel blocker 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (10 microM) was a competitive inhibitor of acidification and raised the Michaelis constant for ATP of the proton pump approximately 11-fold in 120 mM KCl. Inhibition was reversed by valinomycin, which provides an alternate path for charge neutralization. The Cl- dependence of acidification was nonlinear and yielded a Hill coefficient of 3-4, showing that it is distinct from a linear Cl- dependence reported for acidification of renal cortical endosomes. The K+ ionophore valinomycin augmented H+ transport in K2SO4, and not in KCl. Dependence of Cl- transport on membrane potential was confirmed by direct measurement of 36Cl- transport. We uncoupled charge transport from proton transport with a large excess of ammonia, which had no effect on 36Cl- accumulation in vesicles, and by measuring 36Cl- accumulation in response to a membrane diffusion potential, produced with a [K+] gradient and valinomycin in the absence of ATP. These experiments demonstrate that the electrogenic proton pump of the osteoclast ruffled membrane is charge coupled to a passive Cl- permeability in the same membrane.
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PMID:Passive chloride permeability charge coupled to H(+)-ATPase of avian osteoclast ruffled membrane. 182 26

The interaction of myotoxin alpha with intact sarcoplasmic reticulum (SR) components was investigated, and two SR proteins were identified that associated with myotoxin a. One of the proteins has an apparent molecular weight similar to the Ca(2+)-ATPase, the major SR protein responsible for calcium loading. Ca(2+)-ATPase was purified, and its interaction with myotoxin a was studied. Evidence for specific binding of myotoxin a to Ca(2+)-ATPase was established by isolating chemically cross-linked myotoxin a-Ca(2+)-ATPase complexes and further proving their association with anti-myotoxin a antibodies. The binding region of myotoxin a was further delineated by cleaving the protein with cyanogen bromide (CNBr) into two fragments, a larger N-terminal fragment of 28 residues and a smaller C-terminal fragment of 14 residues. Competition experiments with 125I-myotoxin a showed that the C-terminal fragment competed better against 125I-myotoxin a than the N-terminal fragment for SR protein binding. Two overlapping peptides covering the sequence of the N-terminal fragment were synthesized to clarify the interaction of the N-terminal fragment of myotoxin a with SR proteins. A 16-residue peptide corresponding to residues 1-16 competed strongly with 125I-myotoxin a, while a second peptide (residues 13-28) did not.
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PMID:Binding of myotoxin a to sarcoplasmic reticulum Ca(2+)-ATPase: a structural study. 183 Oct 48

We have studied the mechanism by which liver Golgi apparatus maintains the acidity of its contents, using a subcellular fraction from rat liver highly enriched in Golgi marker enzymes. Proton accumulation (measured by quenching of acridine-orange fluorescence) and anion-dependent ATPase were characterized and compared. Maximal ATPase and proton accumulation required ATP; GTP and other nucleotides gave 10% to 30% of maximal activity. Among anions, Cl- and Br- approximately doubled the activities; others were much less effective. Half-maximal increase of ATPase and H+ uptake required 55 mmol/L and 27 mmol/L Cl-, respectively. In predominantly chloride media, SCN- and NO3- markedly inhibited H+ uptake. Nitrate competitively inhibited both the chloride-dependent ATPase (apparent Ki 6 mmol/L) and proton uptake (apparent Ki 2 mmol/L). Nitrate and SCN- also inhibited uptake of 36Cl. Replacing K+ with Na+ had no effect on the initial rate of proton uptake but somewhat reduced the steady state attained. Replacement of K+ with NH4+ and choline reduced proton uptake without affecting ATPase. The ATPase and H+ uptake were supported equally well by Mg2+ or Mn2+. The ATPase was competitively inhibited by 4-acetamido-4'-isothiocyano-stilbene-2,2'-disulfonic acid (apparent Ki 39 mumol/L). Other agents inhibiting both H+ uptake and ATPase were N-ethylmaleimide, N,N'-dicyclohexylcarbodiimide, chlorpromazine, diethylstilbestrol, Zn2+, Co2+ and Cu2+. In the Cl- medium, accumulated protons were released by ionophores at the relative rates, monensin = nigericin greater than valinomycin greater than carbonyl cyanide mchlorophenylhydrazone; the last of these also reduced ATPase activity. In the absence of Cl-, monensin and valinomycin both stimulated the ATPase. These results show a close association between ATPase activity and acidification of liver Golgi vesicles. They support a role for Cl- that depends on its uptake as a counter ion for H+ and suggest that it may also stimulate proton transport by a more direct effect on a component of the transport system.
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PMID:Proton accumulation and ATPase activity in Golgi apparatus-enriched vesicles from rat liver. 184 95

An efflux of potassium ions was demonstrated in mutants of yeast cells lacking a functional high affinity carrier system for monovalent cations. This efflux showed the following characteristics: (a) It was stimulated by the presence of a substrate, either glucose or ethanol. (b) It was stimulated by several cationic organic molecules, such as ethidium bromide, dihydrostreptomycin, diethylaminoethyldextran, and also by trivalent cations, such as Al3+ and lanthanides; this stimulation also depended on the presence of a substrate. (c) K+ efflux was decreased in yeast mutants with decreased ATPase activity, which generated a lower membrane potential. (d) Although the efflux appeared to be of an electrogenic nature, producing hyperpolarization of cells, it was accompanied by the efflux of phosphate, probably as an anion partially compensating for the large amount of cations leaving the cell. (e) K+ efflux was also accompanied by an uptake of protons. (f) The efflux appeared more clearly in cells grown in YPD medium, and not in more complex media nor in the same YPD medium if supplemented with Ca2+ or Mg2+. Efflux of monovalent cations produced by Tb3+ and organic cationic agents was also demonstrated in wild type strains. This efflux system appears to be, at least partially, electrogenic, but seems to be also an exchange system for protons and to function as a symport with phosphate; it may be involved in the regulation of the internal pH of the cell, and appears to be regulated by its link to the energetic status of the cell, probably through the membrane potential.
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PMID:An energy-dependent efflux system for potassium ions in yeast. 191 32

Caldesmon is a major actin-binding protein identified in smooth muscle and many non-muscle cells. It also interacts with calmodulin and a number of other acidic proteins. We have shown previously that the polypeptide stretch from Val629 to Ser666 near the C terminus contains a calmodulin binding site (Wang, C.-L. A., Wang, L.-W. C., Xu, S., Lu, R. C., Saavedra-Alanis, V., and Bryan, J. (1991) J. Biol. Chem. 266, 9166-9172). On the other hand, Bartegi et al. (Bartegi, A., Fattoum, A., Derancourt, J., and Kassab, R. (1990) J. Biol. Chem. 265, 15231-15238) reported a cyanogen bromide fragment beginning at Trp659 which is also capable of binding both calmodulin and actin. A comparison of the overlapping sequence between these two peptides suggests that this calmodulin binding site is localized in a 7-residue segment, 659Trp-Glu-Lys-Gly-Asn-Val-Phe665. We have chemically synthesized an 18-residue peptide (GS17C, from Gly651 to Ser667 with an added cysteine at the C terminus) that contains this segment. This peptide was purified by high performance liquid chromatography and labeled with fluorescent probes at the terminal cysteine residue. We found that GS17C indeed binds calmodulin in a Ca(2+)-dependent manner (Kd = 8 x 10(-7) M) and appears to compete with caldesmon. Interestingly, this synthetic peptide also co-sediments with F-actin, binding to actin being displaceable by calmodulin, as in the case of the native caldesmon. But GS17C does not have any effect on the actomyosin ATPase activity, indicating that this peptide segment does not contain the inhibitory region.
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PMID:A calmodulin-binding peptide of caldesmon. 193 4


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