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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)

The stimulation by calcium and magnesium of ATPase activity of isolated ghosts, of water-soluble protein (spectrin), and of residual vesicles, derived from normal erythrocytes and from hereditary spherocytes (H.S.), has been measured. The ATPase activity found in normal water-soluble protein (WSP) at low levels of calcium (0.1-2.0 mM) is essentially absent in H.S. water-soluble protein, but the ATPase activity with magnesium and with high levels of calcium (60-100 mM) is the same in H.S. and normal WSP. Compared to normal, H.S. ghosts have increased Mg2+-stimulated activity. This increased activity is retained by the sedimentable vesicles ("residue") after extraction of the ghosts with 0.025 mM EDTA. The Ca2+, Mg2+-ATPase associated with the calcium pump is not significantly different in H.S.
Blood 1975 Dec
PMID:Absence of one component of spectrin adenosine triphosphatase in hereditary spherocytosis. 12 93

Mesonephroi of sheep embryos ranging from 12 to 100 mm C.R. length were examined for the occurrence and localization of transport-ATPase. Native cryostat sections were incubated according to the technique of Guth and Albers for demonstrating the nitrophenylphosphatase activity of Mg2+-Na+-K+-adenosine triphosphatase. The basal cytoplasm of the collecting tubule of the narrow segment of the distal tubule exhibit strong activity, the wide segment of the distal tubule is moderately active. Glomeruli, proximal tubule, and Wolffian duct remain unstained. The basal labyrinths of the reactive nephron segments are believed to be the sites of a Na+-K+ exchange pump. In mature and regressing mesonephroi, the findings fully agree with biochemical data; in maturating mesonephroi, whose basal labyrinth is not yet fully established, the biochemical assay proves to be more sensitive. The specifity of the reaction was ascertained by diverse inhibitors and activating ions. The localization of Mg2+-ATPase is different to the above mentioned reaction pattern, as it shows moderate activity in the proximal tubule, too (mature mesonephros). Mesonephroi of very young embryos exhibit strongest Mg2+-ATPase activity in the proximal tubule; here the distal and collecting tubule stain only moderately.
Histochemistry 1975 Dec 19
PMID:Histochemical localization of Mg2+-Na+-K+-adenosine triphosphatase in different stages of the sheep mesonephros. 12 45

Different antiarrhythmic agents such as quinidine, procaine amide, and lodocaine at 1 mM concentrations were found to depress the ability of an isolated perfused rat heart to generate contractile force. Quinidine, but not procaine amide or lidocaine, decreased calcium uptake by both mitochondrial and microsomal fractions at different concentrations of calcium. The mitochondrial phosphorylation rate, respiratory control index, and state 3 oxygen consumption, but not ADP:O ratio and state 4 oxygen consumption, were depressed by only quinidine. None of these agents had any effect on myofibrillar Mg2+-ATPase or Ca2+-stimulated ATPase activities. On the other hand, sarcolemmal Mg2+-ATPase and Ca2+-ATPase activities, but not Na+-K+-ATPase activity, were increased by all these drugs. The sarcolemmal adenylate cyclase (EC 4.6.1.1) activity was decreased by quinidine only. These results suggest some similarities and differences in the sites of action of quinidine, procaine amide, and lidocaine within the myocardium.
Can J Physiol Pharmacol 1975 Dec
PMID:Subcellular and functional effects of quinidine, procaine amide, and lidocaine on rat myocardium. 13 Sep 65

Membrane-bound Ca or Mg of sarcoplasmic reticulum fragments were removed by treating the membrane with EDTA or an acidic solution, and the changes in the enzymatic activities of sarcoplasmic reticulum fragments induced by these treatments were examined. With the decrease in the amount of membrane-bound Ca below 1-3-10(-8) mol/mg protein, it was demonstrated that the activity of (Ca2+ + Mg2+)-ATPase transiently increased and then diminished, that the Ca-uptake and phosphoenzyme formation declined gradually, and that the activity of Mg2+-ATPase was affected to a less extent. Sodium dodecyl sulfate-gel electrophoretic patterns of peptides from the metal-deficient membranes were the same as those of the untreated material. The level of the phosphoenzyme formation of the metal-deficient membrane was restored by increasing the amount of membrane-bound Ca, but not by increasing the amount of membrane-bound Mg.
Biochim Biophys Acta 1977 Dec 01
PMID:The formation of phosphoenzyme of sarcoplasmic reticulum. Requirement for membrane-bound Ca2+. 14 31

We have purified a cofactor protein previously shown (Pollard, T. D., and Korn, E. D. (1973) J. Biol. Chem. 248, 4691-4697) to be required for actin activation of the Mg2+-ATPase activity of Acanthamoeba myosin I. The purified cofactor protein is a novel myosin kinase that phosphorylates the single heavy chain, but neither of the two light chains, of Acanthamoeba myosin I. Phosphorylation of Acanthamoeba myosin I by the purified cofactor protein requires ATP and Mg2+ but is Ca2+-independent. The Mg2+-ATPase activity of phosphorylated Acanthamoeba myosin I is highly activated by F-actin in the absence of cofactor protein. Actin-activated Mg2+-ATPase activity is lost when phosphorylated Acanthamoeba myosin I is dephosphorylated by platelet phosphatase. Phosphorylation and dephosphorylation have no effect on the (K+,EDTA)-ATPase and Ca2+-ATPase activities of Acanthamoeba myosin I. These results show that cofactor protein is an Acanthamoeba myosin I heavy chain kinase and that phosphorylation of the heavy chain of this myosin is required for actin activation of its Mg2+-ATPase activity.
J Biol Chem 1977 Dec 10
PMID:Acanthamoeba cofactor protein is a heavy chain kinase required for actin activation of the Mg2+-ATPase activity of Acanthamoeba myosin I. 14 30

Human blood platelet actin was purified using 30% sucrose to extract actomyosin and potassium iodide to dissociate actomyosin and to depolymerize actin. Pure actin thus obtained resembles skeletic muscle actin in its polymerization properties, CD spectra and ability to activate myosin myosin Mg2+-ATPase. Isoelectric focusing gel analysis shows that human blood platelet actin exists in beta and gamma forms. The ratio of beta to gamma forms is of 5 in purified actin, in whole cell extract and in all the fractions studied.
Eur J Biochem 1977 Dec
PMID:Human platelet actin. Evidence of beta and gamma forms and similarity of properties with sarcomeric actin. 14 44

To determine the reason why the Mg2+-ATPase activity of subfragment-1 prepared with chymotrypsin was activated more by actin than that of subfragment-1 prepared with trypsin was and the reason why the former could enhance the polymerization of actin and the latter could not, we digested subfragment-1, prepared with chymotrypsin, with trypsin and examined the actin activated Mg2+-ATPase activity and the ability to polymerize actin. It was found that cleavage of the heavy chain decreased the actin activated Mg2+-ATPase activity of subfragment-1 prepared with chymotrypsin but did not affect its ability to polymerize actin. Trypsin attacked the subfragment-1 heavy chain at two sites and produced 26 K, 50 K, and 21 K fragments. From the comparison of the time course of tryptic digestion with that of the decrease in actin activation, it was deduced that cleavage of the 50 K-21 K junction was mainly responsible for the decrease in actin activation. We also measured the length and the amount of F-actin polymerized by the addition of different amounts of subfragment-1. It was found that the amount of F-actin increased with the increase in the amount of subfragment-1 added and that the length of F-actin also increased though slightly. We concluded from the results that subfragment-1 enhanced the polymerization not only by facilitating the nucleus formation but also by strengthening the bond between actin monomers in forming F-actin.
J Biochem 1979 Dec
PMID:Interaction of myosin subfragment-1 with actin. III. Effect of cleavage of the subfragment-1 heavy chain on its interaction with actin. 16 Sep 13

Mutant cell lines have been selected from the murine plasmocytoma MOPC 173 for their resistance to ouabain, dibutyryl cyclic AMP, theophyllin and concanavalin A. We have compared three wild-type cell lines with their seven resistant counterparts. All resistant mutants exhibited a (Na+ + K+)-stimulated Mg2+-ATPase resistance to ouabain inhibition when measured in microsomes. The homogeneity of ouabain binding sites has been found in most of the cell lines; however, two different populations of sites have been detected in one wild-type and in one resistant cell lines. These results led us to hypothetise the (Na+ + K+)-ATPase-ouabain interaction being modulated by a non-specific membrane structure.
Biochim Biophys Acta 1976 Dec 02
PMID:Plasma membrane studies on drug-sensitive and -resistant cell lines. II. Ouabain sensitivity of (Na+ +K+)-stimulated Mg2+-ATPase. 18 39

By means of a preparation technique based on the discontinuous sucrose density gradient, subcellular fractions were isolated from guinea pig intestinal smooth muscle cells. A fraction which distributed to a 33% sucrose layer showed relatively high activities of 5'-nucleotidase, Na+ . K+-ATPase and ouabain sensitive Na+ . K+-ATPase. The fraction had a low NaN3 sensitive Mg2+-ATPase activity. On the other hand, the high activity of glucose-6-phosphatase showed a broad distribution. Though the sucrose density gradient proceeded over a series of the fine layers, cross-contamination of microsome into the 33% sucrose fraction was not reduced. To reduce microsomal cross-contamination, another procedure was employed. The homogenization time of 77000 xg sediment to be layered on the top of the sucrose density gradients was prolonged. This procedure did not change the distribution of K+ activated p-nitrophenylphosphatase, K+ activated ouabain sensitive p-nitrophenylphosphatase and ouabain sensitive Na+ . K+-ATPase activities. The peak of NADH cytochrome c reductase activity was shifted to a 38% sucrose fraction from a 33% sucrose fraction and the activity of this marker enzyme in the 33% sucrose fraction decreased to 60% of that of the prior procedure.
Nihon Heikatsukin Gakkai Zasshi 1979 Dec
PMID:[Examination of plasma membrane-enriched fraction from guinea pig intestinal smooth muscle by means of some marker enzymes (author's transl)]. 23 74

Reactive disulfide reagents (RDSs) with a biotin moiety have been synthesized and found to cause Ca2+ release from sarcoplasmic reticulum (SR) vesicles. The RDSs oxidize SH sites on SR proteins via a thiol-disulfide exchange, with the formation of mixed disulfide bonds between SR proteins and biotin. Biotinylated RDSs identified a 106-kDa protein which was purified by biotin-avidin chromatography. Disulfide reducing agents, like dithiothreitol, reverse the effect of RDSs and thus promoted active re-uptake of Ca2+ and dissociated biotin from the labeled protein indicating that biotin was covalently linked to the 106-kDa protein via a disulfide bond. Several lines of evidence indicate that this protein is not Ca2+, Mg2+-ATPase and is not a proteolytic fragment or a subunit of the 400-kDa Ca2+-ryanodine receptor complex (RRC). Monoclonal antibodies against the ATPase did not cross-react with the 106-kDa protein, and polyclonal antibodies against the 106-kDa did not cross-react with either the ATPase or the 400-kDa RRC. RDSs did not label the 400-kDa RRC with biotin. Linear sucrose gradients used to purify the RRC show that the 106-kDa protein migrated throughout 5-20% linear sucrose gradients, including the high sucrose density protein fractions containing 400-kDa RRC. Protease inhibitors diisopropylfluorophosphate used to prevent proteolysis of 400-kDa proteins did not alter the migration of 106-kDa in sucrose gradients nor the patterns of biotin labeling of the 106-kDa protein. Incorporation of highly purified 106-kDa protein (free of RRC) in planar bilayers revealed cationic channels with large Na+ (gNa+ = 375 +/- 15 pS) and Ca2+ (gCa2+ = 107.7 +/- 12 pS) conductances which were activated by micromolar [Ca2+]free or millimolar [ATP] and blocked by micromolar ruthenium red or millimolar [Mg2+]. Thus, the SR contains a sulfhydryl-activated 106-kDa Ca2+ channel with apparently similar characteristics to the 400-kDa "feet" proteins.
J Biol Chem 1989 Dec 25
PMID:Disulfide linkage of biotin identifies a 106-kDa Ca2+ release channel in sarcoplasmic reticulum. 248 Sep 55


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