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)

The pattern of spontaneous skeletal muscle degeneration and clinical recovery hindlimb muscles of the mdx mutant mouse was examined for functional and metabolic confirmation of apparent structural regeneration. The contractile properties, histochemical staining and myosin light chain and parvalbumin contents of extensor digitorum longus (EDL) and soleus (Sol) muscles of mdx and age-matched control mice were studied at 3-4 and 32 weeks. Histochemical staining (myofibrillar ATPase and NADH-tetrazolium reductase) revealed no significant change in slow-twitch-oxidative (SO) or fast-twitch-oxidative-glycolytic (FOG) fibre type proportions in mdx Sol apart from the normal age-related increase in SO fibres. At 32 weeks mdx EDL, however, showed significantly smaller fast-twitch-glycolytic (FG) and larger FOG proportions than those in control EDL. These fibre type distributions were confirmed by differential staining with antibodies to myosin slow-twitch and fast-twitch heavy chain isozymes. Frequency distribution of cross-sectional area for each fibre type showed a wider than normal range of areas especially in FOG fibres of mdx Sol, and FG fibres of mdx EDL, supporting previous observations using autoradiography of myofibre regeneration. Isometric twitch and tetanic tensions in Sol were significantly less than in controls at 4 weeks, but by 32 weeks, values were not different from age-matched controls. In mdx EDL at 3 weeks, twitch and tetanus tensions were significantly less, and time-to-peak twitch tensions were significantly faster than in control EDL. By 32 weeks, mdx EDL twitch and tetanus tensions expressed relative to muscle weight continued to be significantly lower than in age-matched controls, despite normal absolute tensions. The maximum velocity of shortening in 32-week mdx EDL was significantly lower than in control EDL. Myosin light chain distribution in mdx Sol exhibited significantly less light chain 2-slow (LC2s) and more light chain 1b-slow(LC1bs) at 32 weeks than age-matched control Sol. Gels of EDL from 32-week-old mdx mice showed significantly less light chain 2-fast-phosphorylated (LC2f-P) and light chain 3-fast (LC3f) and significantly more light chain 1-fast (LC1f) and light chain 2-fast (LC2f), but normal parvalbumin content compared to age-matched controls. These observations suggest that mdx hindlimb muscles are differentially affected by the disease process as it occurs in murine models of dystrophy. However, the uniqueness of mdx Sol and to a lesser extent EDL is that they also undergo an important degree of functional regeneration which is able to compensate spontaneously for degenerative influences of genetic origin.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Functional regeneration in the hindlimb skeletal muscle of the mdx mouse. 320 90

We have established a new method for preparing Physarum myosin whose actin-activated ATPase activity is inhibited by micromolar levels of Ca2+. This Ca2+-inhibition is mediated by the Ca2+ binding to the myosin rather than by the Ca2+-dependent modification of the phosphorylated state of the myosin (Kohama, K., and Kendrick-Jones, J. (1986) J. Biochem. (Tokyo) 99, 1433-1446). Ca2+-binding light chain (CaLC) has been suggested to be primary importance in this Ca2+ inhibition (Kohama, K., Takano-Ohmuro, H., Tanaka, T., Yamaguchi, T., and Kohama, T. (1986) J. Biol. Chem. 261, 8022-8027). The amino acid sequence of CaLC was determined; it was composed of 147 amino acid residues and the N terminus was acetylated. The molecular weight was calculated to be 16,131. The homology of CaLC in the amino acid sequence with 5,5'-dithiobis-(2-nitrobenzoic acid) light chain and alkali light chain of skeletal muscle myosin were rather low, i.e., 25% and 30%, respectively. Interestingly, however, the CaLC sequence was 40% homologous with brain calmodulin. This amino acid sequence was confirmed by sequencing the cloned phage DNA accommodating cDNA coding CaLC. Northern and Southern blot analysis indicated that 0.8-kilobase pair mRNA was transcribed from a single CaLC gene. This is the first report on the amino acid sequence of myosin light chain of lower eukaryotes and nucleotide sequence of its mRNA.
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PMID:Amino acid sequence of the calcium-binding light chain of myosin from the lower eukaryote, Physarum polycephalum. 333

The role of contractile proteins in secretory granule exocytosis was evaluated by determining whether myosin light chain phosphorylation was altered during stimulation of secretion in mouse pancreatic acini. Acinar myosin was purified by extraction into isosmotic sucrose solution containing 40 mM pyrophosphate followed by ammonium sulfate precipitation and Sepharose 4B-CL chromatography. Myosin was eluted as a single peak of K+-EDTA ATPase activity and was purified over 2,000-fold to a final ATPase specific activity of 0.96 mumol.min-1.mg protein-1. Three major myosin subunits of apparent Mr of 200,000, 20,000, and 17,000 were present in the purified myosin preparation. A fourth protein of Mr 21,000 was also present. Purification of myosin from 32P-labeled acini revealed the Mr 200,000, 21,000, and 20,000 proteins to be heavily labeled. The effect of cholecystokinin octapeptide (CCK-8) on myosin phosphorylation was studied after isolation of myosin from 32P-labeled acinar lysates by immunoprecipitation. Treatment of acini for 1-10 min with a concentration of CCK-8 that gives a maximal secretory response caused a 25-40% increase in light chain labeling. Treatment with a supramaximal CCK-8 concentration produced a 50-80% increase in light chain labeling. Phosphorylation of myosin heavy chain was not significantly affected by secretagogue treatment. These results indicate that stimulation of pancreatic acinar secretion is accompanied by an increase in myosin light chain phosphorylation.
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PMID:Evaluation of myosin light chain phosphorylation in isolated pancreatic acini. 333 33

Human cardiac ventricular myosins were prepared from autopsy samples from nine adults, seven infants, and from surgical specimens from seven patients undergoing left ventricular septal myectomy for obstructive hypertrophic cardiomyopathy. Infant myosin differed from adult myosin in two important characteristics: (a) approximately 30% of the 27,000-dalton myosin light chain is replaced by a 28,000-dalton light chain, and (b) the actin-activated myosin MgATPase activity of infant myosin is significantly lower than that of adult myosin (64 nmol phosphate released/mg myosin per min vs. 124 nmol/mg per min at 37 degrees C). The K(+)-EDTA ATPase activity of the myosin measured in 0.5M KCl is also lower in infants (1,210 nmol/mg per min vs. 620 nmol/mg per min at 37 degrees C), but the Ca(++)-activated ATPase is not significantly different. There were no differences in enzymatic activity between the normal adult and cardiomyopathic myosins.A detailed study was performed to investigate possible variations in the structure of the myosin heavy chain in infant, adult, and cardiomyopathic samples. There were no significant differences between infant and normal adult, or between normal adult and cardiomyopathic myosins seen in pyrophosphate polyacrylamide gel electrophoresis, or peptide mapping using alpha-chymotrypsin, papain, or cyanogen bromide to generate peptides. These results suggest that isoenzymes of human ventricular myosin do not exist for the myosin heavy chain in the specimens examined from infants, adults, and patients with obstructive hypertrophic cardiomyopathy. The decreased actin-activated MgATPase activity found for infant myosin appears to be due solely to a partial replacement of the 27,000-dalton light chain of myosin with a 28,000-dalton light chain.
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PMID:Structural and enzymatic comparison of human cardiac muscle myosins isolated from infants, adults, and patients with hypertrophic cardiomyopathy. 621 Jul 10

Myosin was isolated from the main pulmonary artery of swine and was phosphorylated or dephosphorylated by utilizing the endogenous kinase or phosphatase, respectively. The myosins, phosphorylated to various degrees, were purified free of kinase and phosphatase activities by gel filtration on Sepharose CL-4B agarose columns. The level of actin-activated ATPase activity was dependent upon the degree of myosin light chain phosphorylation. Fully phosphorylated myosin reconstituted with actin and tropomyosin (actin/tropomyosin = 61:1) had the highest ATPase activity (0.1 mumol of Pi/mg . min). The actin-activated ATPase activity showed maximal (60--65%) Ca2+ sensitivity at 2 mol of Ca2+ bound per mol of myosin. The actin-activated ATPase activity, Ca2+ binding, and Ca2+ sensitivity of arterial myosin were also dependent upon Mg2+ concentration. The ATPase activity was maximal at 2--3 mM Mg2+ and, at low (0.5 mM) Mg2+ concentration, the activity was only one-third of the maximal activity. Increasing the Mg2+ above 3 mM was not associated with a further increase in ATPase activity, but the Ca2+ binding and Ca2+ sensitivity decreased with increasing Mg2+ concentration. The maximal Ca2+ sensitivity was observed at 2--3 mM Mg2+, a concentration at which the myosin bound 2 mol of Ca2+/mol. Both the ATPase activity and the Ca2+ sensitivity were more remarkable when actin that contained tropomyosin was used to activate the ATPase activity. The data indicate that calcium regulates the actin-activated ATP hydrolysis not only by its effects on the phosphorylation system but also by direct binding to the myosin.
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PMID:Regulation of actin-activated ATP hydrolysis by arterial myosin. 621 Sep 6

An analysis of the native myosin isoenzyme composition, myosin light-chain distribution and histochemical profile of fast-twitch and slow-twitch muscles of normal and dystrophic (129 REJ dy/dy) mice has been performed, and the results correlated with the known contractile abnormalities of murine dystrophic muscles. Normal mouse slow-twitch soleus contained two isomyosins (slow myosin, SM and intermediate myosin, IM) which were electrophoretically distinct from the three major isomyosins (FM1, FM2, FM3) of fast-twitch extensor digitorum longus (e.d.l.) muscle. The calcium-activated ATPase activities of FM1, FM2, FM3 and IM at pH 9.2 were each much higher than that of SM, and this difference is reflected in the histochemical profile of muscle, as demonstrated with the myofibrillar ATPase reaction at alkaline pH. E.d.l. Type II fibres retained myofibrillar ATPase activity following pre-incubation of histochemical sections at pH 4.6, and were therefore classified Type IIB, whereas soleus Type II fibres did not, and were classified Type IIA. It was concluded that Type I (slow) fibres contain SM, Type IIA (intermediate) fibres contain IM, and Type IIB (fast) fibres contain FM1-FM3. Each electrophoretically distinct myosin contained a different combination of the five skeletal myosin light chains (LCs). Thus different normal muscles, which differed in their isomyosin profiles, differed also in their light-chain composition. Analysis of the distribution of native myosins (FM1, FM2, FM3, IM, SM, in order of decreasing gel migration rate) in dystrophic muscles revealed increased proportions of the slower-migrating forms, when compared with the distribution in the corresponding normal muscles. The shift in isomyosin distribution would explain the known decrease in the proportion of myosin light chain (LCf3) in murine dystrophic muscle. The abnormal isomyosin distribution in the dystrophic muscle is correlated with its altered histochemical characteristics, and with well-established abnormalities in its isometric and isotonic properties. It is concluded that the altered isomyosin distribution in murine dystrophic muscle would result in decreased power output per unit muscle mass when compared with normal muscle. The possibility is considered that defective myelination of the innervating nerve may contribute to these abnormalities by preventing higher frequency impulses from reaching muscle.
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PMID:Myosin isoenzymes in fast-twitch and slow-twitch muscles of normal and dystrophic mice. 622 40

Our previous work showed that myosin phosphorylation decreased the ATPase activity of skeletal muscle myofibrils that were lightly fixed with glutaraldehyde. The fixation process prevented sarcomere shortening and destruction of the ordered filament array upon the addition of ATP. We have now extended these results to myofibrils prepared from hearts of rabbits, dogs and rats. Myofibrils were phosphorylated by incubation with myosin light chain kinase, calmodulin and either ATP-gamma s or ATP, for 15 minutes at 25 degrees C. The extent of myosin light chain phosphorylation was 50% to 80%. The ATPase activity of unphosphorylated myofibrils was not altered by reaction with 0.01% glutaraldehyde for 5 minutes at 0 degrees C, and the ATPase activity of unfixed myofibrils was not changed by phosphorylation. However, phosphorylation decreased the ATPase activity of fixed myofibrils by 50%. The effect on myocardial myofibrillar ATPase activity of phosphorylation was similar in the three animal species. These results suggest that in both skeletal and cardiac muscle, myosin phosphorylation decreases the rate of cross-bridge cycling resulting in decreased energy expenditure. It also appears that the effect of myosin light chain phosphorylation on ATPase activity requires an ordered myofilament structure.
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PMID:Myosin phosphorylation decreases the ATPase activity of cardiac myofibrils. 623

Incubation of bovine aortic native actomyosin with cyclic AMP and bovine aortic cyclic AMP-dependent protein kinase produced a rightward shift in the relation between free Ca2+ and both superprecipitation and actomyosin ATPase activity. The relation between free Ca2+ and phosphorylation of myosin light chains was also shifted to the right. The concentration of free Ca2+ required for half-maximal activation of both ATPase activity and myosin light chain phosphorylation was approximately 1.0 microM for control actomyosin and 2.5 microM for actomyosin incubated with cyclic AMP-protein kinase. Neither basal nor maximal activities were significantly affected by incubation with cyclic AMP-protein kinase. Addition of e microM calmodulin to cyclic AMP-protein kinase-treated actomyosin relieved inhibition of both superprecipitation and myosin light chain phosphorylation. These findings suggest that cyclic AMP-protein kinase-mediated inhibition of actin-myosin interactions in vascular smooth muscle involve a shift in the Ca2+ sensitivity of the system. This shift probably involves Ca2+-calmodulin interactions and the control of phosphorylation of the myosin light chains.
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PMID:Ca2+, calmodulin and cyclic AMP-dependent modulation of actin-myosin interactions in aorta. 626 47

We used a recently developed preparation of calcium-tolerant isolated rat cardiac ventricular cells to investigate certain aspects of hormone-mediated protein phosphorylation in heart tissue. Isoproterenol or dibutyryl adenosine 3',5'-cyclic monophosphate (cAMP) promoted the phosphorylation of at least 13 proteins and promoted the dephosphorylation of a single protein of relative molecular weight (Mr) 21,000, whose phosphorylation appeared to be stimulated by insulin. The isoproterenol-induced protein phosphorylations reached maximum levels for most proteins within 5 min at slightly different rates. However, when excess propranolol was added to the cells after exposure to isoproterenol, there appeared to be two major patterns of dephosphorylation: proteins that remained fully phosphorylated after propranolol addition, exemplified by proteins tentatively identified as troponin I and C-protein, and proteins that were rapidly dephosphorylated after propranolol, exemplified by phospholamban, the modulator of the sarcoplasmic reticulum calcium-dependent ATPase. The Mr 21,000 protein was rapidly dephosphorylated in response to isoproterenol and was rephosphorylated after addition of propranolol. This protein remains unidentified; it is not the Mr 19,000 myosin light chain whose phosphorylation state was unaffected by isoproterenol. This preparation of isolated heart cells provides a convenient way to investigate the biochemical effects resulting from exposure of the heart to hormones and can separate direct hormonal effects from those resulting from changes in contractility or heart rate.
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PMID:Hormonal regulation of protein phosphorylation in isolated rat heart cells. 632 6

Phosphorylation of chicken gizzard myosin light chain in myofibril and its effect on myofibrillar ATPase activity were investigated in the contracted state of myofibrils. When myofibrils were incubated for two hours at 30 degreeds C with ATP, magnesium and calcium, the myosin light chain was phosphorylated by endogenous light-chain kinase. Standing overnight, the phosphorylated light chain was dephosphorylated by endogenous light-chain phosphatase. Control myofibril had much higher ATPase activity than phosphorylated and phosphorylated-dephosphorylated myofibrils. It was very interesting that the phosphorylated and phosphorylated-dephosphorylated myofibrils were quite similar in ATPase activity. However, phosphorylated myofibril differed from phosphorylated-dephosphorylated myofibril in Ca2+ dependency of Mg2+-ATPase activity. The phosphorylated-dephosphorylated myofibril was not affected by the presence or absence of Ca2+. In contrast, phosphorylated myofibril apparently showed a negative Ca2+-sensitivity. On the other hand, the results indicating that the superprecipitation gel formed by phosphorylated-dephosphorylated myosin could not be dissolved in 0.6 M NaCl, suggest that the phosphorylation-dephosphorylation process of the actomyosin system in gizzard myofibril results in stronger actin-myosin interaction.
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PMID:Properties of phosphorylated myofibrils from gizzard smooth muscle. 644 50


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