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)

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

A procedure for the isolation of plasma membranes from protoplasts of suspension-cultured soybean is described. Protoplasts were prepared by enzymic digestion of the cell wall and the plasma membrane was labelled with radioactive diazotized sulphanilic acid. The membrane systems from broken protoplasts were separated by continuous isopycnic sucrose gradient centrifugation. Radioactivity was localized in a band possessing a buoyant density of 1-14 g ml-1. The activities of NADPH- and NADH-cytochrome c reductase, fumarase, Mg2+-ATPase, IDPase and acid phosphodiesterase in the various regions of the density gradient were determined. A plasma membrane fraction was selected which was relatively uncontaminated with membranes derived from endoplasmic reticulum, tonoplasts and mitochondria. The results indicated that Mg2+-ATPase and possibly acid phosphodiesterase were associated with the plasma membrane.
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PMID:The isolation of plasma membrane from protoplasts of soybean suspension cultures. 56 Oct 89

6,7-Dimethoxy-1-(3,4-dimethoxybenzyl)-4-([4-(2-methoxyphenyl)-1- piperazinyl]methyl)isoquinoline (Ro 22-4839) is a new cerebral circulation improver with vasospasmolytic properties. Preliminarily, Ro 22-4839-induced arterial relaxation was confirmed under the treatment of various constrictors and it was hardly overcome by addition of extra calcium. In this study the mode and site of action of this agent were further explored. Ro 22-4839 was found to more strongly inhibit the superprecipitation of chicken gizzard smooth muscle actomyosin (IC50 = 2.0 mumol/l) than trifluoperazine (38 mumol/l) and W-7 (N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide) (220 mumol/l), an in vitro model for relaxation-contraction coupling of the smooth muscle in which calmodulin is known to play an important role through phosphorylation of myosin light chain kinase. The calmodulin antagonistic action of Ro 22-4839 was also demonstrated in other calmodulin-related reaction systems such as phosphodiesterase and hydrophobic fluorescent probe, but was very weak in Ca2+, Mg2+-ATPase of rat erythrocyte membrane. Thus, Ro 22-4839 was suggested to have a relative preference for smooth muscle contraction process unlike trifluoperazine and W-7. Moreover, Ro 22-4839 prevented the decrease in erythrocyte deformability induced by hyperosmolarity or intracellular Ca2+ accumulation, like trifluoperazine and W-7. However, Ro 22-4839 itself caused hardly an internal stomatocytic shape of erythrocytes in contrast to known calmodulin antagonists. Further, Ro 22-4839 inhibited erythrocyte membrane rupture, platelet aggregation and lipid peroxidation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Calmodulin antagonistic action of the cerebral circulation improver 6,7-dimethoxy-1-(3,4-dimethoxybenzyl)-4- ([4-(2-methoxyphenyl)-1-piperazinyl]methyl)isoquinoline. 282 56

We have examined the effects on the activities of three calmodulin-dependent enzymes (cAMP phosphodiesterase, caldesmon kinase and myosin light chain kinase) of the dihydropyridine Ca2+ channel blocker felodipine and three analogues (p-chloro, oxidized and t-butyl) exhibiting different pharmacological potencies. The cAMP phosphodiesterase was inhibited completely by felodipine and the p-chloro analogue with IC50 values of 3.7 and 1.5 microM respectively. The oxidized and t-butyl analogues were relatively ineffective in inhibiting cAMP phosphodiesterase. Felodipine and the p-chloro analogue inhibited the basal (Ca2+/calmodulin-independent) activity of cAMP phosphodiesterase as well as the calmodulin-stimulated activity. Calmodulin was relatively ineffective in preventing inhibition of cAMP phosphodiesterase by felodipine and the p-chloro analogue. These observations suggest that felodipine may act directly on the phosphodiesterase as well as through calmodulin. Felodipine and the p-chloro analogue inhibited Ca2+/calmodulin-dependent caldesmon kinase with similar potencies (IC50 = 17.4 microM), whereas the oxidized and t-butyl analogues caused no inhibition. Similarly, felodipine and the p-chloro analogue inhibited myosin light chain kinase activity whether the isolated 20 kD light chain (IC50 = 12.6 microM) or intact myosin (IC50 = 11.0 microM) was used as substrate. Inhibition in each case was prevented by excess calmodulin. The oxidized and t-butyl derivatives caused little or no inhibition. Finally, the effects of felodipine and the three analogues on two processes which are dependent on myosin phosphorylation were examined, namely the actin-activated Mg2+-ATPase activity of myosin and the assembly of myosin filaments. Felodipine and the p-chloro analogue inhibited the actin-activated Mg2+-ATPase activity of smooth muscle myosin (IC50 = 25.1 microM). The oxidized and t-butyl analogues exhibited no inhibition. Similarly, felodipine and the p-chloro analogue blocked myosin filament assembly induced by low concentrations of calmodulin, whereas the oxidized and t-butyl analogues did not. Again, inhibition of the actin-activated myosin Mg2+-ATPase and myosin filament assembly by felodipine and the p-chloro analogue could be reversed by raising the calmodulin concentration. These observations suggest that some of the pharmacological actions of felodipine on smooth muscle may involve inhibition of calmodulin-dependent enzymes which are functionally involved in the regulation of smooth muscle contraction.
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PMID:Effects of felodipine (a dihydropyridine calcium channel blocker) and analogues on calmodulin-dependent enzymes. 283 1

Male ICR mice, young (25-days old), mature (3-months old), and old (22 months), were injected with morphine sulfate (10 mg/kg, s.c.) or were implanted with morphine pellets (75 mg). Controls received saline injections or placebo pellets. One hour after injections and 72 h after pellet implantations, the mice were decapitated and striatal regions were removed for the following analyses: calmodulin (CaM) levels via radioimmunoassay and activities of cyclic nucleotide phosphodiesterases, adenylate and guanylate cyclases, and Ca2+, Mg2+-ATPase. Acute morphine treatment produced the following: (1) increases in calmodulin levels in the young and old mice while having no effect on mature levels; (2) increases in activities of guanylate cyclase of mature mice while decreasing those of the old mice; (3) no effects on activity of adenylate cyclase; (4) decreased activity of cyclic AMP-phosphodiesterase in young mice only; (5) decreased activity of Ca2+, Mg2+-ATPase in the old mice only. The only changes found in striata from morphine-tolerant mice when compared with age-matched controls were elevations in cyclic GMP-phosphodiesterase activities in all three age groups. Differences in control values of the three age groups were as follows: CaM levels, mature greater than old greater than young; Ca2+, Mg2+-ATPase activity, old greater than mature-young. The results indicate age-induced changes in cellular regulation and biochemical responses to morphine.
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PMID:Effects of aging and morphine administration on calmodulin and calmodulin-regulated enzymes in striata of mice. 285 71

Two hours after administration of Soman (120 micrograms/kg, s.c.), Sarin (150 micrograms/kg, s.c.), or Tabun (240 micrograms/kg, s.c.), microsomes and cytosol were prepared from rat striata. Microsomal and cytosolic calmodulin (CaM) levels, microsomal adenylate and guanylate cyclase activities, protein kinase activities, and Ca2+ + Mg2+-ATPase activities were determined while cytosolic phosphodiesterase (PDE) activities were determined. CaM levels in both cell fractions were significantly increased by Soman and Sarin. Cyclic AMP-PDE and adenylate cyclase activities were decreased by Soman and Sarin. All three agents decreased activities of cyclic GMP-PDE and guanylate cyclase. Sarin and Tabun administration caused significant increases in microsomal protein kinase activity and none of the agents affected activity of divalent cation ATPases. The intensity of effects of the three organophosphates roughly paralleled their observed neurotoxic potencies. The results indicate that components of the CaM system are implicated as either causative or adaptive changes induced by these agents.
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PMID:Acute effects of soman, sarin, and tabun on microsomal and cytosolic components of the calmodulin system in rat striatum. 286 34

The effects of chloroquine on calmodulin (CaM)-related enzyme activities and the shape of human erythrocytes have been studied. It was found that the CaM activation of rat brain phosphodiesterase was abolished by the addition of chloroquine. CaM was included in the assay of phosphodiesterase activity at the concentration that gave half-maximal activation. The concentration of chloroquine that caused 50% inhibition of CaM stimulation of phosphodiesterase was 7 X 10(-5)M. The type of inhibition was competitive with respect to CaM. The CaM-stimulated Ca2+, Mg2+-ATPase in erythrocyte membrane was also inhibited by chloroquine, the 50% inhibitory concentration of which was about 2 X 10(-4)M. Its mode of action was also competitive with respect to CaM. The shapes of erythrocyte ghosts prepared by hypotonic hemolysis were examined in a solution consisting of 2 mM MgCl2, 154 mM NaCl and 10 mM Tris-HCl (pH 7.4); they were discocytic in the presence of 2 mM ATP and in its absence. They were converted to the invaginated form by the addition of chloroquine in the concentration range of 1 X 10(-4)-5 X 10(-4)M. This concentration is similar to that which caused the inhibition of CaM activation of Ca2+, Mg2+-ATPase.
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PMID:Inhibition of calmodulin stimulation of phosphodiesterase and Ca2+, Mg2+-ATPase activities and shape change of erythrocyte ghosts by chloroquine. 296 Mar 25

The actin-activated Mg2+-ATPase activity of dephosphorylated chicken gizzard myosin reconstituted with actin, tropomyosin, myosin light-chain kinase (MLCK) and calmodulin was inhibited completely by purealin, 20 microM, whereas the activity of the phosphorylated and dephosphorylated myosin was not affected. Purealin inhibited the phosphorylation of myosin light chains caused by MLCK and calmodulin (IC50, 5 microM). On the other hand, purealin had no effect on myosin phosphorylation induced by Ca2+ -independent MLCK. The calmodulin-stimulated phosphodiesterase activity was inhibited by purealin (IC50, 7 microM) at concentrations very close to those that inhibit myosin phosphorylation. Kinetic analysis revealed a competitive mode of inhibition of calmodulin-stimulated phosphodiesterase activity by purealin. These results suggest that purealin acts as a calmodulin antagonist in reconstituted actomyosin from chicken gizzard, resulting in inhibition of light chain phosphorylation and the actin-activated ATPase activity of myosin.
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PMID:The mechanism of inhibition of light-chain phosphorylation by purealin in chicken gizzard myosin. 296 81

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

Calmodulin, a calcium binding protein, has been implicated in the regulation of many calcium-dependent biological processes. Since calcium has an important role in hard tissue genesis, both at intra- and extracellular levels, we anticipate that calcium binding proteins may modulate this process. The present study investigated a mineralising tissue, the rat molar tooth germ, to determine the presence of calmodulin-like activity. A heat-treated cell-free extract of tooth germs provided enhancement of Ca2+-dependent Mg2+-ATPase and 3':5'-nucleotide phosphodiesterase activity. No enhancement occurred in the absence of calcium or in the presence of trifluoperazine. SDS-polyacrylamide gel electrophoresis of this extract revealed a protein band of approximately 18,000 mol. wt. These findings indicate the presence of calmodulin-like activity in rat molar tooth germs and support the proposal that calcium and calcium binding proteins, in particular calmodulin, have a major regulatory role in the biology of mineralising tissues.
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PMID:Calmodulin-like activity in a mineralising tissue: the rat molar tooth germ. 611 44


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