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)

Ca2+-independent protein-modulator (BacM) was found in the culture medium of Staphylococcus aureus. BacM activated calmodulin-dependent cyclic nucleotide phosphodiesterase and Ca2+/Mg2+-ATPase in the same way as calmodulin. BacM was shown to be a proteolytic fragment of the exotoxin secreted by the S. aureus strain under study. The kinetic analyses of the ATPase activation by BacM and CaM were performed. These studies demonstrated that the enzyme molecule contains at least two activator-sensitive sites. Experiments on the ATPase activation by Ca2+ both in the presence and in the absence of BacM and CaM documented that CaM-ATPase and BacM-ATPase complexes can exist at low concentrations of calcium. Analysis of activation curves of ATPase by Ca2+ revealed three Ca2+-binding sites in the enzyme-activator complex.
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PMID:Calcium-independent bacterial activator of cyclic nucleotide phosphodiesterase and Ca2+/Mg2+-ATPase. 293 39

Okadaic acid isolated from black sponge (Halichondria okadai), at the concentration of 10 mumol/l, caused contraction in saponin-treated skinned smooth muscle of guinea-pig taenia coli in the absence of Ca2+. In the presence of low concentration (0.3 mumol/l) of Ca2+, okadaic acid induced a greater contraction than in the absence of Ca2+. Okadaic acid potentiated the contractions induced by Ca2+ and pCa2+-tension curve was shifted to the left as well as upward by 1 mumol/l okadaic acid. Native actomyosin preparation (myosin B) containing calmodulinmyosin light chain kinase system and phosphatase was obtained from taenia coli. Okadaic acid (10 mumol/l) increased the actomyosin Mg2+-ATPase activity in the presence or absence of Ca2+. Okadaic acid (1-100 mumol/l) had no effect on calmodulin activity as monitored by Ca2+-calmodulin activated cyclic nucleotide phosphodiesterase activity and the (Ca2+ + Mg2+)-ATPase activity or erythrocyte membranes. These results suggest that okadaic acid directly activates contractile elements of smooth muscle.
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PMID:Direct activation by okadaic acid of the contractile elements in the smooth muscle of guinea-pig taenia coli. 303 85

This paper describes characterization of the reaction of calmodulin with a series of nitrosoureas which are capable of releasing amine-reactive isocyanates of varying hydrophobic character. The site of calcium-dependent carbamoylation on calmodulin by the antineoplastic agent 1-(2-chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea (methyl CCNU) was determined to be Lys-75 as demonstrated using [ring-14C]methyl CCNU and sequence analysis of the sole labeled peptide obtained from tryptic digestion of reversed-phase high pressure liquid chromatography (HPLC)-purified radiolabeled calmodulin. CCNU, the 4-desmethylcyclohexyl derivative of methyl CCNU, and its reactive hydrolysis product, cyclohexyl isocyanate, were also determined to modify calmodulin in a similar manner and at the same site, as demonstrated by specific blockade of modification by the calmodulin antagonist calmidazolium. Nitrosoureas which release the less hydrophobic 4-hydroxy- and 4-carboxycyclohexyl isocyanates are unable to modify calmodulin at 25-fold higher concentrations than those required for modification with methyl CCNU, CCNU, or cyclohexyl isocyanate. With this monomodified Lys-75 derivative, purified to homogeneity by HPLC, differential effects of modification on the activation of bovine brain 3',5'-cyclic nucleotide phosphodiesterase (phosphodiesterase) and human erythrocyte Ca2+,Mg2+-ATPase were observed. Compared to the amounts of native calmodulin needed, phosphodiesterase required 7-fold higher amounts of this derivative to reach maximal activation, whereas the activation of the ATPase was unaffected. Clearly, different regions of calmodulin are responsible for the activation of phosphodiesterase and the ATPase. We conclude that Lys-75 is not essential for the function of calmodulin but is in a region of the molecule involved in interaction with phosphodiesterase as well as the binding of certain hydrophobic calmodulin antagonists.
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PMID:Modification of calmodulin on Lys-75 by carbamoylating nitrosoureas. 313 56

The Ca2+-pumping ATPase from human erythrocyte membranes, purified nearly to homogeneity (Niggli, V., Penniston, J. T., and Carafoli, E. (1979) J. Biol. Chem. 254, 9955-9958), can be reconstituted into phospholipid vesicles. The purified and the reconstituted forms of the enzyme displayed the properties expected of the intact Ca2+ pump; they had an appropriate (Ca2+-Mg2+)-ATPase activity which displayed a relatively low affinity for Ca2+. Added calmodulin increased both the maximum rate and the affinity for Ca2+ of the enzyme. Mg2+ alone caused no significant ATP hydrolysis in the purified enzyme, indicating that the Mg2+-ATPase is a separate enzyme. Vesicles of the reconstituted enzyme accumulated Ca2+ with a ratio of Ca2+ accumulated to ATP hydrolyzed of approximately 1. Ca2+ accumulation and ATPase of the reconstituted enzyme were inhibited concurrently by vanadate ion, with a K 1/2 for inhibition which was indistinguishable from that observed for the (Ca2+-Mg2+)-ATPase in whole erythrocyte ghosts. While the above properties were all consistent with those observed for the (Ca2+-Mg2+)-ATPase in whole erythrocyte ghosts, the purified enzyme displayed an unexpected response to acidic phospholipids. Enzyme reconstituted with or prepared in phosphatidylserine acted as if calmodulin were already present, and added calmodulin caused no effect beyond that due to phosphatidylserine. This mimicry of the calmodulin effect by acidic phospholipids is similar to that reported for cyclic nucleotide phosphodiesterase (Wolff, D. J., and Brostrom, C. O. (1976) Arch. Biochem. Biophys., 173, 720-723).
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PMID:Purified (Ca2+-Mg2+)-ATPase of the erythrocyte membrane. Reconstitution and effect of calmodulin and phospholipids. 610 53