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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)

N-(3-pyrene)maleimide adducts of myosin (PM-myosin) are fluorescent and possess actin-activated Mg2+ ATPase activity. Addition of ATP to PM-myosin produces a reversible decrease of 10% in fluorescence intensity of the pyrene fluorophore in the presence of actin. Analogues of ATP which are poor substrates for myosin ATPase or which merely dissociate actomyosin produce less decrease in fluorescence of PM-myosin than does ATP. Since fluorescence of acto-PM-myosin is sensitive to environmental changes associated with ATP hydrolysis, and/or with fluorophore-actin interactions. PM-myosin may be a useful analysis of molecular aspects of muscle contraction.
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PMID:Preparation and characterization of fluorescent N-(3-pyrene)maleimide adducts of myosin. 14 Feb 1

In the present investigation the results of a lead salt technique and two calcium salt techniques for the deomonstration of the activity of myosin adenosine triphosphatase in sections of both normal and pathological human skeletal muscle specimens are compared. It was seen that the histochemical results obtained by the different techniques are similar, especially with regard to the identification of fibre-types. It can be clearly stated, that the alkaline phosphatase activity present in muscle fibers of diseased skeletal msucles revealed only a very slight activity with the substrate ATP, so the alkaline phosphatase activity in general did not disturb the reliability of the different myosin ATPase techniques. Moreover it was found that the presence of the mitochondrial Ca2+ -ion activated ATPase with a high pH-optimum in muscle fibers did not give rise to faulty results. From studies with dinitrophenol it can be concluded that this substance activates the myosin ATPase present in type I fibres especially.
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PMID:The value of enzyme histochemical techniques in the classification of fibre types of human skeletal muscle. 2. The histochemical demonstration of myosin adenosine triphosphatase in skeletal muscles from adult patients with or with no diseases of the neuromuscular system. A comparison between results obtained by calcium salt and lead salt techniques. 14 Aug 52

The interaction of actin with myosin was studied in the presence of ATP at low ionic strength by means of measurements of the actin-activated ATPase activity of myosin and superprecipitation of actomyosin. At high ATP concentrations the ATPase activities of myosin, heavy meromyosin (HMM) and myosin subfragment 1 (S-1) were activated by actin in the same extent. At low ATP concentrations the myosin ATPase activity was activated about 30-fold by actin, whereas those of HMM and S-1 were stimulated only several-fold. This high actin activation of myosin ATPase was coupled with the occurrence of superprecipitation. The activation of HMM or S-1 ATPase by actin shows a simple hyperbolic dependence on actin concentration, but the myosin ATPase was maximally activated by actin at a 2:1 molar ratio of actin to myosin, and a further increase in the actin concentration had no effect on the activation. These results suggest the presence of a unit for actin-myosin interaction, composed of two actin monomers and one myosin molecule in the filaments.
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PMID:Presence of a unit for actin-myosin interaction during the superprecipitation of actomyosin. 14 84

A new, simple method for the isolation of actin from myxomycete plasmodia has been developed. Plasmodium myosin B was incubated at 55 degrees C for 15 min in the presence of ATP or was treated with 90% acetone. By this treatment myosin was denatured completely. Actin was then extracted with a dilute ATP and cysteine solution from the heat- or acetone-treated myosin B. The method is simple and almost pure actin was obtained in high yield. The purified G-actin polymerized to F-actin on addition of 0.1 M KCl or 2 mM MgCl2. The viscosity of the purified F-actin was 8-10 dl/g. The F-actin activated muscle myosin ATPase, and actomyosin synthesized from the F-actin and muscle myosin showed superprecipitation on addition of ATP.
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PMID:A simple method for the isolation of actin from myxomycete plasmodia. 14 66

Preparations of ATP from equine muscle contained an inhibitor of dynein Mg2+-activated ATPase. The inhibitory material was separated from the ATP by molecular sieve filtration. The several molecular species of dynein extracted from three different axonemal sources were all inhibited; myosin ATPase was not. With increasing amounts of inhibitor the inhibition did not go to completion but reached a plateau when the rate had been reduced to 1/5 the uninhibited rate. A plot of 1/[S] against 1/v at several inhibitor concentrations yielded parallel lines. There was little inhibition of dynein ATPase when Mg2+ was replaced by Ca2+. The inhibitor appeared slightly smaller in molecular size than ATP, had anionic character, and was not adsorbed to charcoal.
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PMID:A dynein ATPase inhibitor isolated from a commercial ATP preparation. 14 8

The Mg2+-dependent ATPase (adenosine 5'-triphosphatase) mechanism of myosin and subfragment 1 prepared from frog leg muscle was investigated by transient kinetic technique. The results show that in general terms the mechanism is similar to that of the rabbit skeletal-muscle myosin ATPase. During subfragment-1 ATPase activity at 0-5 degrees C pH 7.0 and I0.15, the predominant component of the steady-state intermediate is a subfragment-1-products complex (E.ADP.Pi). Binary subfragment-1-ATP (E.ATP) and subfragment-1-ADP (E.ADP) complexes are the other main components of the steady-state intermediate, the relative concentrations of the three components E.ATP, E.ADP.Pi and E.ADP being 5.5:92.5:2.0 respectively. The frog myosin ATPase mechanism is distinguished from that of the rabbit at 0-5 degrees C by the low steady-state concentrations of E.ATP and E.ADP relative to that of E.ADP.Pi and can be described by: E + ATP k' + 1 in equilibrium k' - 1 E.ATP k' + 2 in equilibrium k' - 2 E.ADP.Pi k' + 3 in equilibrium k' - 3 E.ADP + Pi k' + 4 in equilibrium k' - 4 E + ADP. In the above conditions successive forward rate constants have values: k' + 1, 1.1 X 10(5)M-1.S-1; k' + 2 greater than 5s-1; k' + 3, 0.011 s-1; k' + 4, 0.5 s-1; k'-1 is probably less than 0.006s-1. The observed second-order rate constants of the association of actin to subfragment 1 and of ATP-induced dissociation of the actin-subfragment-1 complex are 5.5 X 10(4) M-1.S-1 and 7.4 X 10(5) M-1.S-1 respectively at 2-5 degrees C and pH 7.0. The physiological implications of these results are discussed.
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PMID:Reaction mechanism of the magnesium ion-dependent adenosine triphosphatase of frog muscle myosin and subfragment 1. 14 77

The nerve growth factor protein (NGF) favors polymerization of brain actin and induces its organization to form paracrystalline structures that activate myosin ATPase (ATP phosphohydrolase, EC 3.6.1.3) to an extent greater than actin alone. Binding studies show that the initial 1:1 stoichiometry of NGF-G-actin complexes decreases to 1:7-10 when polymerization is ended and paracrystalline structures are formed. The ratio becomes even lower when heavy meromyosin is added in the absence of ATP, suggesting that heavy meromyosin displaces NGF bound to actin microfilaments. This conclusion is supported by the finding that when heavy meromyosin is added to NGF-microfilament complexes, under conditions for "decorating" microfilaments, the usual paracrystalline structure of the complexes disappears. The NGF-mediated organization of actin and activation of myosin ATPase is visualized as a self-regulatory and self-propagating mechanism, because progressive displacement of the growth factor induced by heavy meromyosin binding to F actin as ATP consumption proceeds renders an increasingly higher amount of NGF free for new interactions. These findings are discussed in the light of the mechanism of action of NGF in the target cells.
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PMID:Nerve growth factor potentiates actomyosin adenosinetriphosphatase. 14 85

Myosin was purified from the flight muscles of a flying (pigeon) and a nonflying (fowl) bird. Ki (ADP) of myosin ATPase of pigeon is higher, but the Km (ATP) is lower than that of fowl. The specific activity (mumole of Pi liberated/min/mg protein) is higher for the fowl. A0.5 (CaCl2) of myosin of both pigeon and fowl is similar. However, the two proteins differ in their interactions with ADP, ATP and p-chloromercuribenzoate. The two proteins have the same tyrosine, tryptophan and sulfhydryl contents. The electrophoretic patterns of the two myosins on SDS-polyacrylamide gels are different. These studies show significant molecular differences in the myosin derived from the flight muscles of a flying (pigeon) and a nonflying (fowl) bird.
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PMID:Comparative studies on myosin ATPase of a flying and nonflying bird. 15 58

Mitotic PtK1 cells, lysed at anaphase into a carbowax 20 M Brij 58 solution, continue to move chromosomes toward the spindle poles and to move the spindle poles apart at 50% in vivo rates for 10 min. Chromosome movements can be blocked by adding metabolic inhibitors to the lysis medium and inhibition of movement can be reversed by adding ATP to the medium. Vanadate at micromolar levels reversibly inhibits dynein ATPase activity and movement of demembranated flagella and cilia. It does not affect glycerinated myofibril contraction or myosin ATPase activty at less than millimolar concentrations. Vanadate at 10--100 micron reversibly inhibits anaphase movement of chromosomes and spindle elongation. After lysis in vanadate, spindles lose their fusiform appearance and become more barrel shaped. In vitro microtubule polymerization is insensitive to vanadate.
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PMID:Chromosome movement in lysed mitotic cells is inhibited by vanadate. 15 67

Changes in some values of protein metabolism in the heart muscle (the activity of myosin ATPase, leucilaminopeptidase, glutamate dehydrogenase, as well as the content of SH-groups, urea, RNA and DNA) were studied by histochemical methods in the parts of the myocardium remote from the zone of the ligated coronary artery. Disorders in the metabolism of nucleic acids were found to consist in nuclear polymorphism and in the development of regressive changes in some nuclei down to necrobiosis as well as in a decrease of the RNA content within the first 12 hours after ligation of the coronary artery. Subsequently, the amount of RNA increased. An increase in the amount of SH-groups, in the activity of leucilaminopeptidase and a decrease in the amount of glutamate dehydrogenase, formation of crystals of xanthhydrolurea as well as in increase in the activity of myosin ATP-ase early in the experiment attest to the occurrence of heterogeneous disorders of protein metabolism in parts of the myocardium beyond the infarction zone.
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PMID:[Histochemical data on changes of various indicators of protein metabolism in the myocardium beyond the infarct zone]. 15 40


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