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)

Studies of the effect of strophanthidin on H(+)-transporting ATPase, Ca(2+)-transporting ATPase and H+/K(+)-transporting ATPase activities are reported. Inhibition observations and kinetic results suggest the existence of a common digitalis aglycone binding site located on the extracellular surface of the enzyme, which is affected competitively by the binding of potassium to H(+)-transporting ATPase, Ca(2+)-transporting ATPase, as well as H+/K(+)-transporting ATPase and Na+/K(+)-transporting ATPase. This may lead to a better understanding of the mechanism of the pharmacological action of cardiac glycosides and imply the possibility that the positive inotropic effect may result from the inhibition of both Ca(2+)-transporting ATPase and Na+/K(+)-transporting ATPase.
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PMID:Inhibition of H(+)-transporting ATPase, Ca(2+)-transporting ATPase and H+/K(+)-transporting ATPase by strophanthidin. 132 54

Gd3+ ions were bound to the Ca(2+)-transport site of Ca(2+)-transporting ATPase of the sarcoplasmic reticulum (SR-ATPase) and their effect on the ESR spectrum of spin-probes, which were attached to specific sites on SR-ATPase and embedded in the membranous lipid at various depths from the surface of the membrane, was studied. Spin-labeled reagents, 1-oxyl-2,2-dimethyl-oxazolidine derivatives of maleimidoethyl-keto stearate, collectively abbreviated as MSL(m,n) were mainly used for labeling SR-ATPase. They have Cm- and Cn-hydrocarbon chains, respectively, on both sides of the spin label, of which the Cm-hydrocarbon chain is located distal to the carboxyl group of the keto stearate moiety. Paramagnetic interaction between Gd3+ and a spin probe was detected by measuring the decrease in the intensity of the ESR signal of the probe. Displacement of Gd3+ from the Ca(2+)-transport site by Ca2+, which had been confirmed previously by using fluorescently labeled SR-ATPase (described in the preceding article), led to a significant reversal of the paramagnetic effect of Gd3+ on MSL(12,3) and MSL(10,5) attached to SR-ATPase. On the other hand, the effect of Gd3+ was not reversed by Ca2+ when SR-ATPase labeled with MSL(1,14) or a spin-label specific for the cytoplasmic domain was used. These results led us to conclude that the Ca(2+)-transport site of SR-ATPase is located in the membranous region of the molecule, but that the site is not very far from the surface of the membrane of the sarcoplasmic reticulum.
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PMID:Location of the Ca(2+)-transport site of Ca(2+)-transporting ATPase of the sarcoplasmic reticulum as determined by analysis of paramagnetic interaction between Gd3+ ions bound at the transport site and membrane-embedded nitroxide spin probes. 166 2

Interaction of Ca2+ and Gd3+ ions with Ca(2+)-transporting ATPase of the sarcoplasmic reticulum (SR-ATPase) was analyzed. Binding of Ca2+ to the transport site caused an enhancement of intrinsic fluorescence of SR-ATPase. Gd3+ also induced fluorescence enhancement. However, the effects of Ca2+ and Gd3+ were additive rather than competitive, indicating that the Gd(3+)-binding site responsible for this enhancement is distinct from the Ca(2+)-transport site. Gd3+ ions at concentrations higher than 10 microM caused a marked fluorescence quenching, indicating an additional interaction at low-affinity binding sites. Interaction of Ca2+ with the transport site led to a quenching of fluorescence of N-(1-anilinonaphthyl-4)maleimide (ANM) covalently attached at SHN [as defined in Yasuoka-Yabe, K. & Kawakita, M. (1983) J. Biochem. 94, 665-675]. In this case the effects of Ca2+ and Gd3+ were mutually exclusive, indicating that Ca2+ and Gd3+ were competing for the same binding site (i.e. the transport site) to affect ANM fluorescence. Competition between Ca2+ and Gd3+ for the Ca(2+)-transport site was also demonstrated by direct measurement of Ca(2+)-binding using nitrocellulose membrane filters. Affinity of Gd3+ for the Ca(2+)-transport site was a little lower than that of Ca2+. Based on these results it was concluded that Gd3+ has at least three kinds of binding sites on SR-ATPase, namely the Ca(2+)-transport site, the Gd(3+)-specific high-affinity site, and a number of low-affinity sites.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Analysis of the binding sites of Gd3+ on Ca(2+)-transporting ATPase of the sarcoplasmic reticulum through its effects on fluorescence of tryptophan residues and a covalently attached fluorescent probe N-(1-anilinonaphthyl-4)maleimide. 183 18

In vitro examination of cardiac tissues isolated from septic and endotoxin-shocked animals has demonstrated intrinsic decreased contractile function and has suggested calcium-related dysfunction. Both the sarcolemma (SL) and sarcoplasmic reticulum (SR) membranes have important roles in regulating cardiac free Ca2+ concentration. Therefore, calcium fluxes were examined in well-characterized SL and SR fractions isolated from hearts of control and endotoxin-shocked guinea pigs. Calcium pump activity was similar in SL from control and shock animals. No intrinsic alteration in the rate of equilibrium calcium concentration of Na(+)-Ca2+ exchange was observed in SL from shock guinea pigs. The electrogenic nature of the exchange was maintained. Active Ca2+ transport, Ca2(+)-ATPase activity, and Ca2+ efflux were similar in SR from hearts of control and shock animals. Although no intrinsic calcium dysfunction was noted in the sarcolemma or sarcoplasmic reticulum from the shock animals, this does not preclude the possibility that some factor (humoral agent) or condition (acidosis) may alter calcium processing in these membranes in vivo.
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PMID:Calcium fluxes in cardiac sarcolemma and sarcoplasmic reticulum isolated from endotoxin-shocked guinea pigs. 219 Jul 13

The characteristics of the interaction between N-(3-pyrene)maleimide (PMI) and the sarcoplasmic reticulum (SR) membranes were investigated, and the sites of labeling with PMI on Ca(2+)-transporting ATPase were identified. PMI was dissolved in the membrane lipids before reacting with the ATPase protein. The measurement of resonance energy transfer from PMI to 1-(dimethylaminophenyl)-6-phenyl-1,3,5-hexatriene revealed that the pyrene moiety of PMI stayed in the lipid layer after it had been covalently attached to the ATPase molecule. PMI-labeled SR membranes at an average labeling density of 1 mol PMI/mol ATPase were digested with trypsin, and the labeled peptides were purified through a series of reversed-phase HPLC procedures on C18 and C4 columns. The amino acid analysis of the purified peptides revealed multiple cysteine residues mainly distributed over the C-terminal half of the cytoplasmic domain of the ATPase molecule as the targets of PMI. This implied that PMI molecules mediated cross-linking between the cytoplasmic domain of the ATPase molecule and the membranes. The distortion of the structure of the former due to this cross-linking may explain the uncoupling of ATP-splitting from Ca(2+)-transport caused by PMI.
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PMID:Sites of labeling with N-(3-pyrene)maleimide on Ca(2+)-transporting ATPase of the sarcoplasmic reticulum. 759 54

It is known that the light fraction of rabbit skeletal muscle sarcoplasmic reticulum vesicles can release Ca2+ from the intravesicular space, although the Ca(2+)-conductive channels are present only in the heavy fraction of sarcoplasmic reticulum vesicles. To study the possible pathways of the Ca2+ leakage from light vesicles we have used a short-term treatment for 4.5 min at 45 degrees C which quickly decreases the efficiency of Ca(2+)-transporting ATPase operation without any visible effects on the hydrolytic activity of the Ca(2+)-ATPase in the membranes. The treatment of the vesicles decreased the negative membrane surface potential created by the Ca(2+)-ATPase. Comparative titration of control and heat-treated preparations of light sarcoplasmic reticulum vesicles by K+, Na+, Mg2+, and Ca2+ revealed clear differences in their surface properties. The short-term heating resulted in release of Ca2+ from the vesicles previously loaded with 45Ca2+, which indicates an increase in passive membrane permeability to Ca2+. Study of Ca(2+)-ATPase protein arrangement in the membrane indicated that the heat treatment induced protein oligomerization and some of the Ca(2+)-ATPase molecules acquired intermolecular and intramolecular covalent bonds. From these data, we have concluded that the changes in the surface and structure properties of the vesicle membranes after the short-term heat treatment were the result of clustering of the Ca(2+)-ATPase molecules. This protein rearrangement may create channels for calcium leakage from light sarcoplasmic reticulum vesicles.
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PMID:Thermal uncoupling of the Ca(2+)-transporting ATPase in sarcoplasmic reticulum. Changes in surface properties of light vesicles. 792 55

Fluorescence energy transfer measurements have been carried out to estimate intramolecular distances between probes bound to Ca(2+)-transporting ATPase (Ca(2+)-ATPase) as well as distances between these probes and the phospholipid headgroup. The nucleotide binding site was monitored by using 1,N6-ethenoadenosine 5'-triphosphate, a fluorescent analogue of ATP, and also by labelling Lys515 with fluorescein 5'-isothiocyanate. Three different cysteine residues were individually labelled using the following probes: 5-[(2-iodoacetyl)aminoethyl]amino-naphthalene-1-sulfonic acid (I-AEDANS), 7-chloro-4-nitro-2,1,3-benzoxadiazole (NBD-Cl) and fluorescent maleimides. The surface of the membrane was labelled by reconstitution with fluorescent phospholipids (fluorescein and rhodamine derivatives). We found a distance of 4.1 nm from the nucleotide binding site to NBD (at Cys344), and the same distance to fluorescent maleimides (at Cys364). The AEDANS label (at Cys670,672) was found separated 3.5 nm from NBD, 4.4 nm from fluorescent maleimides, and 3.9 nm from the lipid matrix. The NBD label was 3.2 nm apart from fluorescent maleimides and 2.2 nm from the lipid matrix. Finally, fluorescent maleimides were found to be located 4.2 nm above the membrane surface. All these distances agree with a molecular model in which NBD is located in the stalk portion of the Ca(2+)-ATPase, near the surface of the membrane, and the rest of the probes are above it, in the globular domain of the protein.
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PMID:Intramolecular distances within the Ca(2+)-ATPase from sarcoplasmic reticulum as estimated through fluorescence energy transfer between probes. 822 16

The sarcoplasmic reticulum (SR) membranes of rabbit skeletal muscle were allowed to react with N-(3-pyrene)maleimide (PMI) at pH 7 at 30 degrees C. The Ca(2+)-transporting activity of the SR membranes was reduced to 20% when PMI was bound to the extent of 1 mol/mol of Ca(2+)-transporting ATPase. The ATPase and the E-P forming activities were not affected by the binding of PMI up to 2 mol/mol ATPase, indicating that PMI somehow uncoupled Ca(2+)-transport from ATP splitting. Permeability of the SR membranes to Ca2+ ions was increased in parallel with the loss of the Ca(2+)-transporting activity. Of several components of the SR membranes which are reactive with PMI, the ATPase protein was the only one whose modification by PMI was directly related to the loss of the Ca(2+)-transporting activity. Similar results were obtained with the light SR membrane fraction, which lacks the ryanodine receptor, a well-recognized Ca2+ channel. These results indicated that a Ca2+ channel that would have been latent or properly regulated in native ATPase somehow escaped from the normal control mechanism as a result of modification of its SH groups by PMI and went into runaway operation. The activated channel was specific for alkaline earth metal ions, so permeability to other solutes including Co2+, Ni2+, and sucrose remained unchanged after treatment with PMI.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Uncoupling of ATP splitting from Ca(2+)-transport in Ca(2+)-transporting ATPase of the sarcoplasmic reticulum as a result of modification by N-(3-pyrene)maleimide: activation of a channel with a specificity for alkaline earth metal ions. 826

We compared acceptor-protein specificities on the formation of ADP-ribose.acceptor adducts by arginine-specific ADP-ribosyltransferase (EC 2.4.2.31) purified from rabbit skeletal muscle sarcoplasmic reticulum (SR) with those of the enzyme purified from chicken peripheral polymorphonuclear cells (heterophils). Major differences are as follows: (1), p33 and beta/gamma-actin, preferential endogenous acceptor proteins for the modification by the heterophil enzyme (Mishima, K., Terashima, M., Obara, S., Yamada, K., Imai, K and Shimoyama, M. (1991) J. Biochem. 110, 388-394 and Terashima, M., Mishima, K., Yamada, K., Tsuchiya, M., Wakutani, T. and Shimoyama, M. (1992) Eur. J. Biochem. 204, 305-311) were not modified by the SR enzyme. (2), The modification of p33 by the heterophil enzyme was enhanced by addition of polyanions such as DNA while the protein did not function as acceptor for modification by the SR enzyme even in the presence of DNA. (3), To ADP-ribosylate endogenous substrate Ca(2+)-transporting ATPase (EC 3.6.1.38) of rabbit skeletal muscle SR, the SR ADP-ribosyltransferase required polycations such as poly(L-lysine), whereas the heterophil enzyme modified the ATPase in the absence of poly(L-lysine). These results suggest that vertebrate arginine-specific ADP-ribosyltransferase prefers its own acceptor protein for the modification. Some other properties of the SR and the heterophil ADP-ribosyltransferases were also compared.
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PMID:Comparison of acceptor protein specificities on the formation of ADP-ribose.acceptor adducts by arginine-specific ADP-ribosyltransferase from rabbit skeletal muscle sarcoplasmic reticulum with those of the enzyme from chicken peripheral polymorphonuclear cells. 843 75

The role played by the phosphorylation sites of calmodulin on its ability to activate the human erythrocyte Ca(2+)-transporting ATPase (Ca(2+)-ATPase) was evaluated. Phosphorylation of mammalian calmodulin on serine/threonine residues by casein kinase II decreased its affinity for Ca(2+)-ATPase by twofold. In contrast, tyrosine phosphorylation of mammalian calmodulin by the insulin-receptor kinase did not significantly alter calmodulin-stimulated Ca(2+)-ATPase activity. Two variant calmodulins, each containing only one tyrosine residue (the second Tyr is replaced by Phe) were also examined: [F138]calmodulin, a mutant containing tyrosine at position 99, and wheat germ calmodulin which has tyrosine at position 139. The concentrations of [F138]calmodulin and wheat germ calmodulin required for half-maximal activation of Ca(2+)-ATPase were tenfold and fourfold higher, respectively, than mammalian calmodulin. Phosphorylation at Tyr99 of [F138]calmodulin shifted its affinity for Ca(2+)-ATPase towards that of mammalian calmodulin. However, phosphorylation at Tyr139 of wheat germ calmodulin had essentially no effect on its interaction with Ca(2+)-ATPase. Thus, all of the observed effects of both phosphorylation and substitution of residues of calmodulin are on its affinity for Ca(2+)-ATPase, not on Vmax. The effects are dependent on the site of phosphate incorporation. Replacement of tyrosine with phenylalanine has a larger effect than phosphorylation of tyrosine, suggesting that the observed functional alterations reflect a secondary conformational change in the C-terminal half of calmodulin, the region that is important in its activation of Ca(2+)-ATPase.
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PMID:Analysis of phosphorylation and mutation of tyrosine residues of calmodulin on its activation of the erythrocyte Ca(2+)-transporting ATPase. 870 25


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