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 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

F-actin monomer (F-monomer) is formed upon the addition of neutral salt to G-actin. Since F-monomer has a digestibility similar to that of F-actin and much lower than that of G-actin, it has been proposed that F-monomer has a conformation different from that of G-actin and similar to the conformation of the subunits in F-actin. To examine whether F-monomer will enhance the magnesium-activated myosin adenosine triphosphatase (Mg2+-ATPase) as much as F-actin, the ability of partially polymerized actin populations at equilibrium to activate the Mg2+-ATPase of heavy meromyosin was investigated. Correlations were made between ATPase activities and the polymerization state of actin as determined by measurements of viscosity and digestibility. No significant activation of the heavy meromyosin ATPase was observed under conditions where G-actin or mixtures of G-actin and F-monomer were present. As polymer formation occurred at higher actin concentrations, or with increased KCl concentrations, substantial activation characteristic of F-actin was observed. The data suggest that F-monomer may undergo a further conformational change as it forms nuclei or joins onto polymers. Alternatively, the site of actin which activates the myosin ATPase may involve the crevice between two adjacent actin subunits.
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PMID:Activation of heavy meromyosin adenosine triphosphatase by various states of actin. 15 Feb 86

Myosin has been purified from the principal pancreatic islet of catfish, hog salivary gland, and hog pituitary. Use of the protease inhibitor Trasylol (FBA Pharmaceuticals, New York) was essential in the isolation of pituitary myosin. Secretory tissue myosins were very similar to smooth muscle myosin, having a heavy chain of 200,000 daltons and light chains of 14,000 and 19,000 daltons. Salivary gland myosin cross-reacted with antibodies directed toward both smooth muscle myosin and fibroblast myosin, but not with antiskeletal muscel myosin serum. The specific myosin ATPase activity measured in 0.6 M KCl was present. Tissues associated with secretion of hormone granules contained substantial amounts of this ATPase, rat pancreatic islets having 4.5 times that of rat liver. Activation of low ionic strength myosin ATPase by actin could not be demonstrated despite adequate binding of the myosin to muscle actin and elution by MgATP. The myosins were located primarily in the cytoplasm as determined by cell fractionation and were quite soluble in buffers of low ionic strength.
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PMID:Myosins of secretory tissues. 15 Apr 27

Changes in cardiac metabolism in myocardial failure and after alcohol ingestion are discussed. The main effect of alcohol ingestion is loss of cardiac contractility. Since heart muscle does not contain alcohol dehydrogenase, its toxicity is probably the result of a direct toxic effect of ethanol and acetaldehyde on the myocardial cell, possibly involving various membrane systems. Alcohol inhibits mitochondrial respiration and the activity of enzymes in the tricarboxylic acid cycle, and its interferes with both mitochondrial calcium uptake and binding. Ethanol profoundly affects myocardial lipid metabolism. Acetaldehyde diminishes myocardial protein synthesis and inhibits Ca++-activated myofibrillar ATPase. In myocardial failure, a series of possibilities may be responsible for the loss of contractility. Excitation-contraction coupling could be disturbed at the level of the sarcolemma, at the sarcoplasmic reticulum, at the mitochondria, and between calcium and the regulatory proteins. Deficiencies in Ca++ delivery systems of excitation-contraction coupling on the myosin ATPase activity could be responsible for the dimunition in cardiac contractility. Mitochondrial function may also be involved, since mitochondria from failing human hearts are defective with respect to respiratory control and calcium accumulation. Under certain conditions, the relationship of mitochondria to calcium sequestration is very important in influencing contractility. The involvement of contractile and regulatory proteins in myocardial failure cannot be excluded.
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PMID:Cardiac metabolsim: its contributions to alcoholic heart disease and myocardial failure. 15 68

Papillary muscle mechanics and ventricular myosin calcium-activated ATPase activity were measured in the same heart as a function of temperature (8--28 degrees) in rabbits and marmots, in order to examine further the hypothesis that the velocity of cardiac muscle shortening at zero load (Vmax) is correlated with myosin ATPase activity. There was a similar Q10 for Vmax in each muscle type, as measured with isotonic afterloaded quick-releases at 30--33% time-to-peak tension; the calcium activated ATPase of myosin in the two muscle types also was similar. The least squares linear regression of rabbit Vmax on calcium-activated myosin ATPase activity was the same as in the marmot, so all the data were pooled to yield a linear regression (Y = 0.47 +/- 3.82X) with a high correlation between the two variables [r = 0.95, P less than 0.01 (ANOV)]. Furthermore, the correlation proved to be predictive of cardiac Vmax and myosin ATPase activity levels in other experiments where these two measurements decreased below normal as a result of hypertrophic growth. Consequently, the quantitative relationship between Vmax and myosin ATPase defined here may prove to be predictive of the ability of cardiac muscle to release bond energy.
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PMID:The relationship of mechanical Vmax to myosin ATPase activity in rabbit and marmot ventricular muscle. 15 23

In our previous study (Onishi, H., Susuki, H., Nakamura, k., and Watanabe, S. J. Biochem. 83, 835-847, 1978), we found it to be characteristic of chicken gizzard myosin that thick filaments of gizzard myosin are readily disassembled by a stoichiometric amount of ATP (3 mol of ATP per mol of myosin), and that the ATPase activity of gizzard myosin in the ATP-disassembled state is much lower than that of gizzard myosin disassembled by a high concentration of KCl. We now report the following findings: (1) Thick filaments of (unphosphorylated) gizzard myosin can be in a bipolar structure or in a non-polar structure, depending on the method of preparing the thick filaments. (2) Thick filaments of (unphosphorylated) gizzard myosin in either the bioplar or the non-polar structure are readily disassembled by ATP. (3) Addition of rabbit skeletal C-protein does not confer ATP resistance on thick filaments of (unphosphorylated) gizzard myosin. (4) Unphosphorylated) gizzard myosin in the ATP-disassembled state is in a dimeric form as determined by ultracentrifugation. Moreover, 0.2 M KCl-dissociated gizzard myosin in monomeric form is converted to a dimeric form by ATP. (5) The Mg-ATPase activity of (unphosphorylated) gizzard myosin is much lower in its dimeric form (less than one-tenth) than in its monomeric form. The activity depression observed around 0.15 M KCl is therefore due to the formation of myosin dimers. (6) Skeletal L-meromyosin can increase the very low activity of (unphosphorylated) gizzard myosin ATPase at low ionic strength (0.13 M KCl) by forming ATP-resistant hybrid filaments with (unphosphorylated) gizzard myosin, preventing the formation of myosin dimers. (7) Gizzard myosin in which one of the light-chain components is phosphorylated by myosin light-chain kinase can form thick filaments which are resistant to the disassembling action of ATP. (8) Even in the presence of ATP, thick filaments of phosphorylated gizzard myosin do not disassembled into myosin dimers. Accordingly, the ATPase activity of phosphorylated gizzard myosin does not show activity depression at low ionic strength.
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PMID:Structure and function of chicken gizzard myosin. 15 5

Histochemical profiles of individual muscle fibres were established using myosin adenosine triphosphatase (myosin ATPase), succinate dehydrogenase (SDHase), and glycogen phosphorylase (GPase) reactions in three muscles (semitendinosus, diaphragm, and pectoralis transversus) of the horse and dog. The major histochemical difference between fibres lies in their myosin ATPase activity; fibres can be subdivided into those with a high and those with a low activity. In horse muscle, all fibres have a high activity of GPase. In the diaphragm and pectoralis transversus, all fibres have a high SDHase activity, but fibres with a low activity of SDHase are also present in samples of the semitendinosus. In dog muscle, all fibres have a high SDHase activity; myosin ATPase low-reacting fibres also have a low activity of GPase. There is a greater fractional area of myosin ATPase high-reacting fibres in the pectoralis transversus and semitendinosus of thoroughbred horses and greyhounds (breeds selected for high speed running) and in the diaphragm of greyhounds. In adults this feature does not appear to be due to training, as are the differences in aerobic and anaerobic capacity (shown in other studies). The preponderance of myosin Atpase high-reacting fibres suggests that there may be differences in the nervous systems of athletes and non-athletes. It is concluded that the proportions of fibre types in muscles are related to the functions of muscles and of their parts. No sex differences or detraining effects were apparent, although the value for the proportion of fibre types (as differentiated by the myosin ATPase reaction) in the limb muscles of thoroughbred crosses lies between those of thoroughbreds and non-thoroughbreds.
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PMID:Differences in the histochemical properties of skeletal muscles of different breeds of horses and dogs. 15 95

Daily administration of d,l isoproterenol-HCl (5 mg/kg) in rats for periods of 14-21 days results in marked cardiac hypertrophy and a decrease in cardiac actomyosin ATPase activity. Actomyosin suspensions (ionic strength 0.08) from right and left ventricles showed average decreases in ATPase activity of 37.1% (p less than 0.005) and 35.7% (p less than 0.05), respectively, for animals treated with isoproterenol for 14 days. Isolated myofibrils from combined ventricular muscle of another group of animals that received the same isoproterenol treatment showed an average decrease in ATPase of 36.4% (p less than 0.0025). The later experiments also demonstrated that the decrease in ATPase activity was not Ca++ sensitive suggesting the lack of involvement of a change in the calcium regulatory factors (tropomyosin-troponin complex). In contrast to these findings, purified myosin from treated animals and actomyosin assayed under conditions which essentially reflect myosin ATPase activity uninfluenced by actin interaction (actomyosin in solution, ionic strength 0.6), did not demonstrate a change in ATPase from controls. It was concluded that the decrease in cardiac actomyosin ATPase in isoproterenol treated rats involved primarily a defect in actin or the interaction of actin with other components of the contractile protein complex.
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PMID:Characterization of the decreased ATPase activity of rat cardiac actomyosin in isoproterenol-induced cardiac hypertrophy. 15 67

Inhibition of the myosin ATPase by vanadate ion (Vi) has been studied in 90 mM NaCl/5 mM MgCl2/20 mM Tris-HCl, pH 8.5, at 25 degrees C. Although the onset of inhibition during the assay is slow and dependent upon Vi concentration (kapp approximately 0.3 M-1 s-1), the final level of inhibition approaches 100%, provided the Vi concentration is in slight excess over the concentration of ATPase sites. Inhibition is not reversible by dialysis or the addition of reducing agents. The source of this irreversible inhibition consists of the formation of a stable, inactive complex with the composition M . ADP . Vi (where M represents a single myosin active site). The complex has been isolated, and its mechanism of formation from M, ADP, and Vi has been studied. Omission of ATP increases the rate of formation by about 35-fold (kapp approximately 11 M-1 s-1), yet this rate is still low in comparison with the rates of simple protein-ligand association reactions. This slowness is interpreted in terms of a rate-limited isomerization step that follows the association of M+, ADP, and Vi: M+ . ADP . Vi leads to M+. ADP . Vi (+ indicates the inactive product of the isomerization). The properties of M.ADP.Vi are compared with those of the ATPase intermediate M**.ADP . Pi, and the possible role of Vi as an analog of Pi is discussed.
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PMID:Inhibition of myosin ATPase by vanadate ion. 15 22


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