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:3.6.3.1 (Mg2+-ATPase)
1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Membrane vesicles of Escherichia coli prepared by osmotic lysis of lysozyme ethylenediaminetetracetate (EDTA) spheroplasts have approximately 60% of the total membrane-bound reduced nicotinamide adenine dinucleotide (NADH) dehydrogenase (ED 1.6.99.3) and Mg2+-adenosine triphosphatase (ATPase) (EC 3.6.1.3) activities exposed on the outer surface of the inner membrane. Absorption of these vesicles with antiserum prepared against the purified soluble Mg2+-ATPase resulted in agglutination of approximately 95% of the inner membrane vesicles, as determined by dehydrogenase activity, and about 50% of the total membrane protein. The unagglutinated vesicles lacked all dehydrogenase activity and may consist of outer membrane. Lysozyme-EDTA vesicles actively transported calcium ion, using either NADH or adenosine 5'-triphosphate (ATP) as energy source. However, neither D-lactate nor reduced phenazine methosulfate energized calcium uptake, suggesting that the observed calcium uptake was not due to a small population of everted vesicles. Transport of calcium driven by either NADH or ATP was inhibited by simultaneous addition of D-lactate or reduced phenazine methosulfate. Proline transport driven by D-lactate oxidation was inhibited by either NADH oxidation or ATP hydrolysis. These results suggest that the portion of the total population of vesicles capable of active transport, i.e., the inner membrane vesicles, are functionally a homogeneous population but cannot be categorized as either right-side-out or everted, since activities normally associated with only one side of the inner membrane can be found on both sides of the membrane of these vesicles. Moreover, the data indicate that oxidation of NADH or hydrolysis of ATP by externally localized NADH dehydrogenase or Mg2+-ATPase establishes a protonmotive force of the opposite polarity from that established through D-lactate oxidation.
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PMID:Functional mosaicism of membrane proteins in vesicles of Escherichia coli. 19 Feb 12

The effect of Sa modification with NEM, which activates Mg2+-ATPase through an enhancement of the association of actin and myosin, was investigated on the superprecipitation, clearing and Mg2+-ITPase of myosin B with reference to the effect of S1-blocking. 1. Superprecipitation induced by ATP was markedly enhanced by Sa-blocking even at high concentrations of Mg2+ and substrate; this may be due to an increase in the affinity of myosin and actin on blocking Sa. 2. Nevertheless, neither ITP-induced superprecipitation nor Mg2+-ITPase was affected by Sa modification. 3. Blocking of S1 brought about the inhibition of ATP- and ITP-induced superprecipitation and Mg2+-ITPase activity, suggesting that S1-blocking decreases the affinity of myosin and actin. 4. Sa-blocked myosin B showed greater resistance to clearing by ATP, especially in the presence of Ca2+ ions, whereas in the clearing response of actomyosin gel to PPi no difference between Sa-blocked and unmodified myosins B was observed. On the other hand, the clearing response of myosin B became more sensitive to both ATP and PPi on blocking S1. Based on the above results and preliminary data suggesting that Sa is located in LMM, the interaction of myosin filaments and actin filaments under physiological conditions is discussed.
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PMID:The sulfhydryl groups involved in the active site of myosin B adenosinetriphosphatase. II. Effect of modification of the Sa thiol group on superprecipitation and clearing. 19 36

The Ca2+-dependent regulation of smooth muscle actomyosin involves a myosin light chain kinase (ATP: myosin light chain phosphotransferase). It has been shown (Dabrowska, R., Aromatorio, D., Sherry, J.M.F., and Hartshorne, D.J. 1977, Biochem. Biophys. Res. Commun. 78, 1263) that the kinase is composed of two proteins of approximate molecular weights 105 000 and 17 000. In this communication it is demonstrated that the 17 000 component is the modulator protein. This conclusion is based on: (1) the identical behavior of the 17 000 kinase component and modulator protein in assays of actomyosin Mg2+-ATPase activity, phosphorylation of myosin, and phosphodiesterase activity, and, (2) the similarity of the 17 000 kinase component and the modulator protein with respect to amino acid composition, absorption spectrum, and electrophoresis in urea-polyacrylamide gels. It is shown also that the modulator protein from smooth muscle and troponin C are distinct proteins.
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PMID:Modulator protein as a component of the myosin light chain kinase from chicken gizzard. 20

Rat liver plasma membranes hydrolyze ATP in the presence of Ca2+. The rate of hydrolysis is different when Mg2+ions are present in the incubation system. Several parameters differentiate Ca2+-ATPase from Mg2+-ATPase: a) the Km of ATP hydrolysis for Ca2+ (2.25 x 10(-4) M) is lower than for Mg2+ (2.14 x 10(-3) M); b) the shape of the activation curve is hyperbolic in the presence of Ca2+ and sigmoid in the presence of Mg2+; c) Mg2+-ATPase shows two different values of activation energy while Ca2+-ATPase presents only a single value; d) Ca2+-ATPase is inhibited, while Mg2+-ATPase is unaffected by cyclic AMP. Ca2+-ATPase is localized on the plasma membrane and is not inhibited by cysteine. It does not hydrolyze substrates different from nucleotides triphosphate, such as glucose-1-phosphate or alpha-glycero-phosphate. The enzyme is probably related to a mechanism of calcium transport.
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PMID:Ca2+-activated ATPase of rat liver plasma membrane. 21 Jul 75

Calcium-ATPase activity (Mg2+-dependent Ca2+-ATPase, ATP phosphohydrolase, EC 3.6.1.3) in erythrocyte membrane preparations from cystic fibrosis (CF) patients was greatly reduced compared to erythrocyte membranes from control subjects. The Km for calcium was found to be similar in the two groups; however, the Vmax, the maximal rate of activation of the Ca2+-ATPase, is reduced by 50% in the erythrocyte membrane preparations of the CF patients (P less than 0.001). In contrast, the Mg2+-ATPase activity of erythrocyte membranes from CF patients was unchanged compared to the control subjects. No difference in the Na+,K+-ATPase activity in erythrocyte membranes from CF patients compared to control patients could be observed. This indicates that the Ca2+-ATPase activity noted in CF erythrocytes is not part of a generalized membrane or membrane-bound enzyme alteration. It remains to be determined whether this alteration in Ca2+-ATPase activity is directly related to a defect in calcium transport in these cells and is a generalized phenomenon in CF present in cell types more directly involved in secretion.
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PMID:Calcium and sodium transport processes in patients with cystic fibrosis. I. A specific decrease in Mg2+-dependent, Ca2+-adenosine triphosphatase activity in erythrocyte membranes from cystic fibrosis patients. 21 42

Effects of lanthanum on Ca2+-ATPase, Mg2+-ATPase, Na+-K+-ATPase, and calcium binding activities were studied in rat heart sarcolemma. Ten to 100 micrometers lanthanum depressed significantly the Ca2+-ATPase activity and 50--200 micrometers lanthanum inhibited the calcium binding activity. Lineweaver-Burk plots of the Ca2+-ATPase activity showed that the inhibition by lanthanum was competitive with calcium concentration. Neither Mg2+-ATPase nor Na+-K+-ATPase activities were affected by lanthanum when the assay medium contained 1 mM EDTA; however, in the absence of EDTA, these enzyme activities were significantly decreased by 10--100 micrometers lanthanum. Rat hearts perfused with HEPES buffer containing 0.5 mM lanthanum showed electron-dense deposits restricted to the outer cell surface and the sarcolemma obtained from these hearts also had the deposits, indicating that the membrane fraction isolated by the hypotonic shock--LiBr treatment method is of sarcolemmal origin. The Ca2+-ATPase activity of the sarcolemma isolated from lanthanum-perfused hearts, unlike the Mg2+-ATPase, Na+-K+-ATPase, and calcium binding activities, was significantly less than the control value. From these observations it is suggested that lanthanum may influence calcium movement across the sarcolemma by affecting sarcolemmal ATPase and calcium binding activities.
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PMID:Effects of lanthanum on the heart sarcolemmal ATPase and calcium binding activities. 22 55

Ca2+-dependent phosphorylation of the myosin light chains in bovine aortic native actomyosin is markedly depressed in the presence of cyclic AMP and its dependent protein kinase. This inhibition occurs with either cardiac, skeletal, or aortic protein kinase plus cyclic AMP, while little or no inhibition occurs with either cyclic AMP or protein kinase alone. The extent of inhibition is related to the concentration of protein kinase and approaches a maximum of approximately 50%. Concomitant with the inhibition of myosin light chain phosphorylation is (a) an increased phosphorylation of a 100,000-dalton moiety which possibly corresponds to the myosin light chain kinase present in the native actomyosin preparation and (b) a decrease in the actomyosin Mg2+-ATPase activity. These findings suggest that modulation of actin-myosin interactions by the cAMP system directly at the level of the contractile proteins may represent a mechanism by which beta adrenergic relaxation occurs in mammalian vascular smooth muscle.
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PMID:Adenosine 3':5'-monophosphate-mediated inhibition of myosin light chain phosphorylation in bovine aortic actomyosin. 22 48

Treatment of plasma membrane isolated from murine plasmocytoma MOPC 173 with an EDTA-containing buffer resulted in a 300-fold increase in sensitivity of (Na+ + K+)-stimulated Mg2+-ATPase to ouabain. This phenomenon was associated with the solubilization by EDTA of phospholipid free proteins (approx. 30 000-34 000 daltons) from the cytoplasmic face of the plasma membrane and with removal of about 90% of the membrane bound Ca2+. The recovery of the original resistance to ouabain required specifically Ca2+ and was associated with a binding of the solubilized proteins to the membrane.
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PMID:Inhibition of (Na+ + K+)-ATPase by ouabain: involvement of calcium and membrane proteins. 22 55

When myofibrils from rat hearts were dissolved in concentrated salt solutions and reprecipitated by dilution, they contained both protein kinase (partly cyclic 3':5'-AMP-dependent) and protein phosphatase activities. Troponin-I was the major protein to be phosphorylated by the endogenous myofibril-associated kinase and by added protein kinase. Approximately 1 mole of phosphate per mole of troponin-I was incorporated from radioactive ATP, but the extent of troponin-I phosphorylation could be varied experimentally. An inverse correlation was found between protein phosphorylation and the maximum Ca2+-stimulated myofibrillar Mg2+-ATPase activity, while the amout of calcium required for half-maximum activation was proportional to the extent of protein phosphorylation. The changes in Mg2+-ATPase activity produced in vitro by protein phosphorylation were reproduced in isolated perfused rat hearts treated for short periods with L-noradrenaline (10(-6)M). The changes in myofibrillar function brought about as the result of the phosphorlyation by cAMP-dependent protein kinase suggest that the contractile response is desensitized in order to cope with the rise in intracellular Ca2+ which results from the action of catecholamines on cardiac ventricular cells.
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PMID:Cardiac myofibrillar phosphorylation and adenosine triphosphatase activity. 22 75

The sonication of 30 S dynein obtained from Tetrahymena cilia induced dissociation into 14-S subunits, some of the enzyme still remaining as intact 30 S dynein and partially dissociated dynein (21 S) in a minor amount. It was demonstrated that the enzymatic properties of the 14 S subunit are quite similar to those of 30 S dynein except for the Ca2+:Mg2+ ratio. ATPase (EC 3.6.1.3) (ATP phosphohydrolase activity of the 14 S subunit was steadily enhanced by increasing concentrations of Mg2+. It was also activated by Ca2+ with an optimum at 6 mM but inhibited by a further increase in concentration. The Ca2+:Mg2+ ratio at 1 mM was about 0.62. 0.6 M KCl stimulated ATPase activity of the 14 S subunit two-fold. The Mg2+-ATPase had an optimum at pH 6.2 and revealed a high activity over pH 10. The Ca2+-ATPase showed two optima at pH 6.2 and 9.5. The Km for ATP was 10 muM. Only 10% of the 14 S subunit recombined with the outer fibers in the presence of Mg2+. The 14 S subunit was shown to have the same mobility as that of 30 S dynein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis.
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PMID:Dissociation of Tetrahymena 30 S dynein into 14 S subunit by sonication. 24 8


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