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)

Illumination of sarcoplasmic reticulum vesicles by ultraviolet light in the presence of 1 mM vanadate causes photocleavage of the Ca(2+)-ATPase into two fragments (Vegh et al. (1990) Biochim. Biophys. Acta 1023, 168-183). In the absence of Ca2+ the photocleavage occurs in the N-terminal half of the molecule near the phosphate acceptor Asp-351. In the presence of 2 mM Ca2+ the photocleavage shifts to the C-terminal half of the ATPase, near the FITC binding site (Lys-515). About half of the Ca(2+)-ATPase was cleaved rapidly, accompanied by nearly complete, irreversible loss of ATPase activity when illuminated in the presence of 2 mM CaCl2; further cleavage of the enzyme was slow and affected primarily the C-terminal fragment produced in the presence of Ca2+. Solubilization of the Ca(2+)-ATPase with C12E8 did not affect the site of photocleavage in either conformation. The vanadate-induced Ca(2+)-ATPase crystals were disrupted during photocleavage, while the binding of anti-ATPase antibodies directed against the phosphorylation site (PR-8) and against the FITC binding region (PR-11) was enhanced. The bovine kidney Na+,K(+)-ATPase was insensitive to photocleavage under conditions where about half the Ca(2+)-ATPase was fragmented. The slight cleavage of the pig gastric H+,K(+)-ATPase after prolonged illumination produced fragments that are distinct from the fragments of the Ca(2+)-ATPase.
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PMID:Differences in the susceptibility of various cation transport ATPases to vanadate-catalyzed photocleavage. 165 3

The polypeptide antibiotic duramycin has been reported to interact selectively with phosphatidylethanolamine (PE) and monogalactosyldiacylglycerol (Navarro et al., 1985, Biochemistry 24, 4645-4650). PE is a major component of mitochondrial membranes. Duramycin was used to probe the role of PE in mitochondrial energy conversion reactions with the following results: (i) Duramycin uncoupled mitochondrial respiration, decreasing the respiratory control ratio to 1 at 5 microM. At concentrations of duramycin in excess of 10 microM, ADP addition inhibited electron transport. (ii) Duramycin inhibited oxidative phosphorylation (C50 less than 2 microM). (iii) Duramycin stimulated mitochondrial ATP hydrolysis modestly. The antibiotic was 7- to 16-fold less effective in this regard than concentrations of carbonylcyanide p-trifluoromethoxyphenylhydrazone (F-CCP) which produced comparable uncoupling. (iv) Duramycin inhibited uncoupled ATPase activity (C50 = 8 microM). Inhibition of the ATPase activity of intact mitochondria was blocked by 1 mM MgCl2 and 5 mM CaCl2; inhibition persisted in sub-mitochondrial particles assayed in the presence of 3 mM MgCl2. The effects on mitochondrial function of free fatty acids (FFA) and duramycin are similar in many respects. It is suggested that duramycin, like FFA, uncouples via a nonclassical mechanism, possibly by disrupting intramembrane H+ transfer between redox and ATPase complexes. In addition, interaction of duramycin, either direct or indirect, with the F0 moiety of the mitochondrial ATPase and with one or more components of the respiratory electron transport chain is proposed.
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PMID:Duramycin effects on the structure and function of heart mitochondria. II. Energy conversion reactions. 165 2

1. The contractile responses of aortic ring preparations from Sprague-Dawley rats made hypertensive by 6-week dietary salt loading were studied. The test and control diet contained 8.0 and 0.3% NaCl, respectively. Aortic rings from salt-loaded rats showed enhanced sensitivity to noradrenaline (NA) but not to serotonin. Contractile responses to CaCl2 in Ca-free NA-containing medium was significantly enhanced in salt-loaded rats, but was unchanged in K(+)-depolarised medium. K(+)-induced relaxation (a functional indicator of Na-K adenosine triphosphatase activity) was sensitive to 10 mumol/L ouabain and was significantly attenuated in aortic rings from salt-loaded rats. The results suggest that hypertension induced by salt-loading is associated with enhanced sensitivity to NA, increased Ca2+ entry through receptor-operated channels, and impairment of Na-K ATPase enzyme activity.
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PMID:Altered responses of aortic smooth muscle from Sprague-Dawley rats with salt-induced hypertension. 166 59

Following cell fractionation in sucrose density gradients, plasma membrane Mg(2+)-ATPase from Pachysolen tannophilus was studied. The ATPase displayed an apparent Km for ATP of 1.42 mM and was inhibited by high concentrations of Mg2+. The inhibitory effects of ethanol, 1-propanol, 1-butanol, and benzyl alcohol on Mg(2+)-ATPase were evaluated, and the concentration of each alcohol that inhibited ATPase activity by 50% (IC50) was determined. The IC50 decreased as the chain length of the alcohol increased. Moreover, the IC50 for ATPase activity was similar to the IC50 for growth rate, suggesting an association between impaired growth and ATPase inhibition. Almost complete inhibition of ATPase activity occurred at temperatures approaching 60 degrees C, and the optimal temperature was around 44 degrees C for ATPase from both control and ethanol-treated cells. Inclusion of 50 mM MgCl2 or CaCl2 in the medium did not rescue cells from the deleterious effects of ethanol.
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PMID:Plasma membrane Mg(2+)-ATPase of Pachysolen tannophilus: characterization and role in alcohol tolerance. 183 33

We previously showed that A23187 in high ionophore/protein ratios almost completely inhibits the sarcoplasmic reticulum Ca(2+)-ATPase [Hara, H. & Kanazawa, T. (1986) J. Biol. Chem. 261, 16584-16590]. In an attempt to obtain information on the mechanism of this inhibition, the effects of A23187 on conformational changes involved in the Ca(2+)-induced activation of the enzyme were investigated. The purified enzyme from sarcoplasmic reticulum of rabbit skeletal muscle as well as the purified enzyme labeled with fluorescein 5-isothiocyanate (FITC) were preincubated with A23187 in the absence of Ca2+ at pH 7.0 and 0 degrees C for 45 min. The activation of the enzyme following addition of CaCl2 was assessed by determining the capacity for rapid formation of phosphoenzyme from ATP. This activation was strongly inhibited by the preincubation with A23187. This indicates that the previously observed inhibition of the Ca(2+)-ATPase is mostly due to hindrance of the Ca(2+)-induced activation of the enzyme. In the control, in which the FITC-labeled enzyme was preincubated without A23187, the fluorescence intensity of the bound FITC decreased in a biphasic manner upon addition of CaCl2. The first rapid phase of this fluorescence drop was unaffected by A23187, whereas its second slow phase was almost completely inhibited by this drug. These results show that the Ca(2+)-dependent conformational change is biphasic and that the second slow phase (but not the first rapid phase) of this conformational change is inhibited by A23187. This suggests that the observed inhibition of Ca2+ activation is attributed to hindrance of the second slow phase of the Ca(2+)-dependent conformational change.
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PMID:Inhibition by A23187 of conformational changes involved in the Ca(2+)-induced activation of sarcoplasmic reticulum Ca(2+)-ATPase. 183 85

The ratio between Ca2+ uptake and Ca(2+)-dependent ATP hydrolysis measured in sarcoplasmic reticulum vesicles of rabbit skeletal muscle was found to vary greatly depending on the concentrations of oxalate or Pi used. In the presence of 5 mM oxalate, 20 mM Pi, and 1 mM Pi, the ratios found were in the range of 1.4-2.3, 0.6-0.8, and 0.01-0.10, respectively. The rates of Ca2+ exchange and ATP synthesis were measured at the steady state by adding trace amounts of 45Ca and 32Pi, after the vesicles had been loaded with Ca2+. In the presence of 1 mM Pi, 10 mM MgCl2, and 0.2 mM CaCl2, the ratio between Ca2+ exchange and ATP synthesis varied from 9 to 14. This ratio approached two when Ca2+ in the medium was reduced to a very low level, or when in the presence of Ca2+, dimethyl sulfoxide was added to the assay medium, or when the Pi concentration was raised from 1 to 20 mM. A ratio of two was also measured when the steady state was attained using ITP instead of ATP. In all the conditions that led to a ratio close to two, there was an increase in the fraction of enzyme phosphorylated by Pi. It is proposed that the coupling between Ca2+ translocation and ATP hydrolysis or synthesis is modulated by the phosphorylation of the ATPase by Pi.
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PMID:Ca2+ translocation and catalytic activity of the sarcoplasmic reticulum ATPase. Modulation by ATP, Ca2+, and Pi. 183 89

Incubation of plasma membranes isolated from bovine aorta with either 0.5 mM CaCl2 or with a phorbol ester (1 microM phorbol 12,13-dibutyrate) and phosphatidylserine in an EGTA-containing buffer resulted in the phosphorylation of 10 proteins (Mr of 158, 105, 75, 62, 44, 39, 33, 22, 15 and 9 kDa), presumably due to activation of endogenous protein kinase C (PKC). After heat treatment of the aortic plasma membranes at 80 degrees C for 5 min in order to inactivate all endogenous protein kinase, phosphatase and ATPase activities, membrane phosphorylation was absolutely-dependent upon the addition of an exogenous, partially-purified PKC preparation from bovine aorta. Under these conditions, a total of 17 phosphoproteins could be detected (Mr of 158, 105, 75, 44, 39, 33, 30, 29, 27, 25, 22, 17.5, 16, 15, 11, 10 and 9 kDa). The most prominent phosphoprotein band in native membranes had a molecular weight of 75 kDa (p75); several characteristics suggest that p75 might be autophosphorylated PKC. The phosphorylation of aortic plasma membranes by exogenous PKC required phosphatidylserine and was calcium-dependent (10(-5) to 10(-7) M Ca2+); the addition of diolein resulted in little or no enhancement of phosphorylation. Replacement of phosphatidylserine with oleic acid resulted in the same number of phosphoproteins, but the extent of phosphorylation was diminished. The phosphorylation pattern was altered slightly if the aortic plasma membranes were isolated in the presence of 1 mM Ca2+ instead of EGTA buffers as in the standard procedure. Experiments were performed to determine if the p39 substrate of PKC in aortic plasma membranes was calpactin II (lipocortin I). Immunoblotting established that calpactin II was present in aortic plasma membranes, but there was no corresponding phosphoprotein on the autoradiographs.
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PMID:Phosphorylation of aortic plasma membranes by protein kinase C. 183 27

The Ca(2+)-ATPase crystals formed in detergent solubilized sarcoplasmic reticulum (SR) at 2 degrees C in a crystallization medium of 0.1 M KCl, 10 mM K-Mops (pH 6.0), 3 mM MgCl2, 3 mM NaN3, 5 mM DTT, 25 IU/ml Trasylol, 2 micrograms/ml 1,6-di-tert-butyl-p-cresol, 20% glycerol and 20 mM CaCl2 (J. Biol. Chem. 263, 5277 and 5287 (1988)) contain highly ordered sheets of ATPase molecules, that associate into large multilamellar stacks (greater than 100 layers). When the crystallization is performed in the same medium but in the presence of 40% glycerol at low temperature the stacking is reduced to 4-5 layers and the average diameter of the crystalline sheets is increased from less than 1 micron to 2-3 microns. Glycerol and low temperature presumably reduce stacking by interfering with the interactions between the hydrophilic headgroups of Ca(2+)-ATPase molecules in adjacent lamellae, while not affecting or promoting the ordering of ATPase molecules within the individual sheets. Electron diffraction patterns could be regularly obtained at 8 A and occasionally at 7 A resolution on crystals formed in 40% glycerol, either at 2 degrees C or at -70 degrees C. In the same media but in the absence of glycerol, polyethyleneglycol 1450, 3000 and 8000 (1-8%) induced the formation of ordered crystalline arrays containing 10-12 layers that were similar to those obtained in 40% glycerol. Replacement of 40% glycerol with 10-50% glucose or supplementation of the standard crystallization medium with polyethyleneglycol (PEG 3000 or 8000; 1, 2, 5 and 8%) had no beneficial effect on the order of crystalline arrays compared with media containing 40% glycerol.
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PMID:Effects of solutes on the formation of crystalline sheets of the Ca(2+)-ATPase in detergent-solubilized sarcoplasmic reticulum. 183 35

The isolated working rabbit heart preparation was used to study whether the "contractile machinery" remains unchanged in globally stunned myocardium. The function of the heart has been measured in nonischemic and postischemic conditions. The effect of isoprenaline or calcium chloride administration in both conditions was also studied. Myocardial contractile function was significantly depressed after 20-min global ischemia and returned to normal after CaCl2 and supranormal values after isoprenaline administration. From hearts used in experiments myofibrils were prepared and their ATPase activity was determined. It was observed that myofibrils prepared from "stunned" myocardium showed about 50% increase in ATPase activity in the presence of CaCl2. Subjection of the heart to ischemia caused a decrease in calcium sensitivity of the myofibrillar ATPase. Myofibrils obtained from ischemic hearts but subjected to isoprenaline or CaCl2 administration exhibited increased calcium sensitivity over that of control heart. These effects were accompanied by changes in the extent of phosphorylation of troponin I (TNI) and myosin light chains. The modification of contractile apparatus in the postischemic period described in this paper may contribute to the overall mechanism of myocardial stunning.
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PMID:Contractile proteins in globally "stunned" rabbit myocardium. 183 10

The epithelial layer lining the proximal convoluted tubule of mammalian kidney contains a brush border of numerous microvilli. These microvilli appear in structure to be very similar to the microvilli on epithelial cells of the small intestine. Microvilli found in both the small intestine and the proximal convoluted tubules in kidney have a core bundle of actin filaments bundled by the accessory proteins villin and fimbrin. Along the length of intestinal microvilli, lateral links can be observed to connect the core bundle of actin filaments to the membrane. These cross-bridges are comprised of a 110-kDa calmodulin complex which belongs to a class of single-headed myosin molecules, collectively referred to as myosin-1. We now report that an analogous calmodulin-binding polypeptide of 105 kDa has been identified in rat kidney cortex. The 105-kDa polypeptide is preferentially found in purified kidney brush borders, can be extracted with ATP, and co-elutes with calmodulin on gel filtration and anion exchange chromatography. Fractions containing the 105-kDa polypeptide exhibit a modest ATPase activity in buffer containing CaCl2. The partially purified 105-kDa polypeptide will bind iodinated calmodulin and will sediment with F-actin in buffer containing ethylene glycol-bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) or Ca2+. The addition of ATP partially reverses this association with F-actin. These results indicate that myosin-1, in addition to its presence in intestinal brush borders, is present in the brush border of kidney. We also provide preliminary evidence to indicate that the 105-kDa polypeptide is not restricted to tissues possessing a brush border.
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PMID:Identification of the microvillar 110-kDa calmodulin complex (myosin-1) in kidney. 183 82


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