Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.4.1 (myosin ATPase)
 1,140 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Postnatal development of extrafusal and intrafusal muscle fibers was examined histochemically in segmental tail muscles of the rat. At birth all fibers show a strong reaction for myosin ATPase, uniformity in diameter, and homogeneity in staining intensity. During the first postnatal week, the muscle fibers undergo gradual hypertrophy and hyperplasia but they all maintain the same intense homogeneous staining pattern for the enzyme. By day 9, further differentiation of the muscle fibers results in the formation of a second intrafusal fiber type while the extrafusal fibers are still relatively homogeneous. Finally, two kinds of extrafusal fiber and a third type of intrafusal fiber can be distinguished by day 21. This histochemical fiber pattern is essentially maintained in the adult. These findings show that fiber type development in rat tail muscles lags behind the usual time course of myogenesis known to occur in more rostral regions of the animal. It also indicates that histochemical differentiation of intrafusal fibers in these muscles does not parallel that which occurs in extrafusal fibers. It is likely that arrival and initial contact of sensory nerve terminals on developing intrafusal fibers at day 7 directly influences their relatively early histochemical heterogeneity.
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PMID:Postnatal cytochemical development of muscle fibers in segmental tail muscles of the rat. 13 98

Some properties of creatine kinase were investigated in a two-enzyme system, myosin ATPase-creatine kinase. A rise in the creatine activity in the presence of native myosin was demonstrated. The addition of proteolytic fragments of myosin caused a similar effect. Thermostability of creatine kinase in the presence of native myosin increased. Blocking of amino groups of myosin by TNBS had no effect on its activating capacity, but decreased its influence on thermostability of creatine kinase. Localization of the binding sites of creatine kinase on the myosin molecule is discussed in the present work.
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PMID:[Effect of myosin and its fragments on some creatine kinase properties]. 13 78

The interaction between paramyosin and myosin has been studied by enzymological methods. Clam adductor paramyosin inhibits the actin-activated, Mg2+-requiring ATPase of both clam adductor and rabbit skeletal muscle myosins. Myosin and paramyosin must be rapidly coprecipitated for this inhibition. Incubation with F-actin in the absence of ATP does not alter this effect. This inhibition follows a hyperbolic function with respect to paramyosin concentration. Slow precipitation by dialysis of myosin and paramyosin together leads to copolymers with actin-activated ATPase equivalent to that of slowly formed myosin filaments. Both kinds of slowly formed filaments have enzymatic properties distinct from those of the rapidly precipitated proteins. Paramyosin is competitive with F-actin for their effects upon myosin. The apparent affinity of myosin for F-actin is markedly reduced by association with paramyosin, but the extrapolated maximal velocity of actomyosin is unaffected. The specificity of this inhibition is strongly suggested by marked quantitative differences between native and cleaved paramyosins. No inhibition of intrinsic myosin ATPase by paramyosin is seen. These studies suggest that at least two types of condition-dependent association between myosin and paramyosin are possible. One class of interactions is associated with enzymic inhibition in rapidly coprecipitated filaments, whereas slowly formed cofilaments exhibit catalytic activity similar to that of identically treat-d myosin and have a characteristic 14.5 nm axial repeat.
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PMID:Myosin-paramyosin cofilaments: enzymatic interactions with F-actin. 13 57

Important similarities are reported between human smooth muscle actomyosin and the human erythrocyte spectrin complex, primarily components 1, 2, and 5 (Fairbanks G., Steck, T.L., and Wallach, D.F.H. (1971), Biochemistry 10, 2606). The actin-like protein, component 5, is identical with human uterine actin in its ability to form 50-70-A filaments to stimulate myosin ATPase activity, and to bind rabbit heavy meromyoson specit heavy meromyosin specifically. Antibodies to human smooth muscle myosin(uterine) were prepared which were monospecific. A weak but specific cross-reaction of these antisera with components 1 and/or 2 (spectrin) was characterized and at least 25% of the antimyosin antibodies showed a low affinity reaction iwth spectrin. Antibodies generated against a soluble complex of spectrin components 1 and 2 reacted only with component 1 and did not cross-react with myosin. In addition to these structural similarities between smooth muscle actomyosin and the spectrin complex, we have found that spectrin is involved in ATP-dependent erythrocyte shape changes (Sheetz, M.P., Painter, R.G., AND Singer, S.J. (1976B), Cold Spring Harbor Symp. Cell Motility (in press) and, therefore, the spectrin complex is also a mechanochemical protein system.
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PMID:Relationships of the spectrin complex of human erythrocyte membranes to the actomyosins of muscle cells. 13 78

The immunogenicity of smooth muscle actin is increased by ageing at 4 degrees for at least a week. Rabbits lacking natural smooth muscle antibodies were injected with 1 mg of aged purified actin in adjuvant. Fourteen out of thirty-six rabbits produced serum antibodies which precipitated with actin solution, but not with smooth muscle tropomyosin, myosin, light or heavy meromyosin or with other unidentified non-actin proteins in crude extracts. Analysis of crude actin extract before and after precipitation by antiserum (i) by Sephadex G-200 chromatography and (ii) for its stimulating effect on myosin ATPase activity showed that actin was selectively removed. The precipitate itself, analysed on SDS-polyacrylamide gel, showed one band in the actin position, and otherwise only bands representing immunoglobulins. The antiserum also inhibited the ability of actin to stimulate myosin ATPase activity, and prevented polymerization of G-actin to F-actin, as shown by viscosity and EM studies. On immunoflouresence with cryostat tissue sections or cell cultures, anti-actin serum stained smooth muscle fibres and many non-muscle cells, in the latter staining the microfilaments. The staining was prevented by absorbing the antiserum with actin (16 mug per 5 mul serum), and was abolished by pretreatment of the cells with cytochalasin B. No species specificity was demonstrated for these anti-actin antibodies.
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PMID:The specificity of anti-actin serum. 13 24

Ca2+ATPase activity and light chains of myosin, fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, in developing, adult and denervated fast, slow and cardiac muscles of the rat, guinea-pig, cat, rabbit and chick were studied. It has been shown that in normal adult muscles the electrophoretic pattern of light chains of myosin reflects the myosin ATPase activity only when muscles from the same animal species are compared. In homologous muscles from adult animals differing in size, the size-dependent difference in myosin ATPase activity is not revealed in the electrophoretic pattern. Both in developing and in denervated muscle, changes in myosin ATPase activity are either connected with changes in the pattern of light chains of myosin or this pattern does not change. This relation is different in fast and slow muscles and also differs in chick and rabbit muscles. There are several possibilities of explaining the relation between ATPase activity of myosin and the pattern of light chains of myosin. The observation that myosin from the soleus muscle of 1-month-old rabbit contains light chains corresponding to both fast and slow type of myosin, indicates that the change in myosin ATPase activity during development is due to changes in the ratio between the fast and slow type of myosin.
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PMID:The relation between ATPASE activity and light chains of myosin in developing, adult and denervated muscles of several animals species. 13 84

The effects of a moderate physical training program on the hearts of rats have been studied. The mechanical responses of these hearts are improved. Possible contributing factors in this improvement are increased coronary reserve and capacity to deliver oxygen to the myocardium, increased myocardial glycogen stores and increased turnover of fatty acids through the endogenous triglyceride pool. Myocardial oxidative compounds and high energy phosphate stores are not altered. Major changes are found in the energy utilization pathways. Actomyosin, myosin, and heavy meromyosin ATPase activity and binding activity of isolated sarcoplasmic reticulum are all enhanced. Sulfhydryl control of the active site of myosin ATPase is altered. The biochemical effects of conditioning are short lived when training is decreased or discontinued.
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PMID:Effects of physical training and detraining on intrinsic cardiac control mechanisms. 13 72

In experimental cardiac hypertrophy induced by aortic constriction of rats, the hypertrophy was established after 5-7 days. The basic biochemical changes for increasing tissue mass; increases in protein, nucleic acid, and polyamine synthesis started to occur between 2 and 8 hours followed by an increase in uridine nucleotide pools via predominance of "salvage" pathway. Although the precise coupling mechanism between mechanical stress and biochemical changes is still obscure, an interval between increased load and DNA transcription may be quite short. Some of the key enzymes regulating these processes showed a biphasic response the reason of which is not clear. The established hypertrophied heart muscle showed a decrease in velocity of isotonic shortening and an increase in resting tension. The former alteration is referred to a decrease in myosin ATPase activity and an disorder in excitation-contraction coupling mechanism, and the latter is supposed to be due to an increase in collagen in heart muscle.
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PMID:Biochemical aspects of experimental cardiac hypertrophy. 13 28

The effect of 5-hydroxytryptamine (5HT) on the ATPase activity and sulphydryl group reactivity of mammalian skeletal muscle actomyosin has been studied. 5HT inhibited the Mg2+-activated but not the Ca2+-activated ATPase activity of actomyosin. It slightly activated myosin ATPase. The sulphydryl groups of actomyosin reacting with 5,5'-dithiobis-(2-nitrobenzoic acid) were blocked by concentrations of 5HT which inhibited the Mg2+-activated ATPase. The significance of the results are discussed in relation to the muscle lesions in the experimental myopathy induced by 5HT and imipramine.
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PMID:Inhibition of actomyosin ATPase by high concentrations of 5-hydroxytryptamine. Possible basis of lesion in 5HT-induced experimental myopathy. 13 9

Bovine cardiac myosin ATPase activity was rapidly inactivated by the purine disulfide analog of ATP,6,6'-dithiobis(inosinyl imidodiphosphate). Kinetic investigations showed that this analog acted as a site-specific reagent at 0 degrees with a Ki of 130 muM and a half-life of 8.2 min at saturating inhibitor concentrations. Concentrations (50 to 500 muM) of ATP, adenyl-5'-yl imidodiphosphate (AMP-PNP), or ADP that saturated the active site caused an enhancement in the rate of inactivation, indicating the purine disulfide analog was not reacting at the active site. Under these conditions saturation kinetic data were still observed with Ki values remaining unchanged (120 muM) but with the half-life of inactivation decreasing to 6.0 min (ATP) and 4.6 min (AMP-PNP) at saturating inhibitor concentrations. At concentrations greater than 0.5 mM ATP, AMP-PNP, or ADP there was a decrease in the rate of inactivation, implying protection by these nucleotides. However, saturation kinetics of inactivation could no longer be demonstrated, implying a change in the mechanism of inactivation. A comparison of the inactivation of the Mg2+, Ca2+, and EDTA-ATPase activities of cardiac myosin after modification by the purine disulfide analog showed that the Mg2+- and Ca2+ATPase activities plateaued at approximately 60% and 40%, respectively, while the EDTA-ATPase activity continued to decrease to below 10%. This evidence supports the suggestion that the purine disulfide analog was not reacting at the active site. Equilibrium dialysis experiments were used to measure the binding of [8-3H]AMP-PNP to native cardiac myosin, the thiopurine nucleotide-modified myosin, and the derivative formed by displacing the thiopurine nucleotide by cyanide (thiocyanato-myosin). Native myosin bound a total of 2.1 mol of AMP-PNP with a binding constant of 6.0 X 10(6) M-1. There was a 15 to 40% decrease in the number of AMP-PNP binding sites in the enzyme derivatives, but the active sites appeared not to be blocked since the association constants remained essentially unchanged (KA=3.9 X 10(6) M-1 for thiopurine nucleotide-myosin and 12.0 X 10(6) M-1 for thiocyanato-myosin). The kinetic studies and the binding experiments indicate that the purine disulfide analog reacts at a specific site other than the active site but do not offer support to earlier suggestions from skeletal myosin studies that this site is a possible ATP control site.
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PMID:Reaction of cardiac myosin with a purine disulfide analog of adenosine triphosphate. I. Kinetics of inactivation and binding of adenylyl imidodiphosphate. 13 83


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