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:3.6.4.1 (myosin ATPase)
1,140 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Structural and functional changes in myosin of fast muscles during early post-natal development were studied to seek correlations with well-known physiological changes in the contraction rate. The findings were as follows: 1. It is known that fetal fast muscle myosin contains three kinds of light chains. It was confirmed that their molecular weights were the same as those of adult fast muscle myosin, but different from those of adult slow muscle myosin. The amount of the smallest light chain, g3, was confirmed to increase markedly during the postnatal period. 2. The ATPase [EC3.6.1.3] activity of fetal fast muscle myosin (-1 day) was found to be about 50% of that of adult myosin. The pH-activity curve of fetal myosin ATPase was confirmed to be similar to that of adult myosin. 3. The rate of formation of the reactive myosin-phosphate-ADP complex, MADPP, was found not to change during post-natal development. 4. It was found that the rate of decomposition of MADPP in the presence of F-actin increased markedly during the post-natal period, and that the rate of decomposition of the complex of fetal mysoin was only 1/6 to 1/4 of that of adult myosin. The change in the actomyosin ATPase activity was found to be closely correlated with the increase in the g3 content during development.
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PMID:Developmental changes in the structure and kinetic properties of myosin adenosinetriphosphatase of rabbit skeletal fast muscle. 0 17

The flexibility of the tertiary structure around the active site of myosin ATPase [EC 3.6.1.3] was studied using the reactivity of two specific thiol groups, S1 and S2, as a structural probe. The following four maleimide derivatives were used as thiol-directed reagents: N-ethylmaleimide (NEM), N-(4-methoxy-2-benzimidazolyl methyl) maleimide (MBM), N-(p-(2-benzimidazolyl)phenyl)maleimide (BIPM) and N-(4-dimethyl-amino-3,5-dinitrophenyl)maleimide (DDPM). 1. All the maleimide derivatives used activated the Ca2+-ATPase activity and inhibited the EDTA-ATPase activity, like NEM, indicating that they modified S1. The rate of modification of S1 by NEM and BIPM increased with increasing pH, while that by DDPM decreased. BIPM simultaneously modified S1 and S2. 2. S1 showed much higher reactivity toward the maleimides, except for BIPM, than did N-acetylcysteine (N-Ac-Cys) a low molecular-weight model compound. The extremely small pKa value of S1, 6.28, accounted for this high reactivity. In addition, the ATP-induced increase in its reactivity inducated that S1 was in a buried state. Kinetic analysis showed that the teritiary structure around S1 at alkaline pH differed from that at acidic pH. 3. The apparent rate constant of S2-modification with NEM was approximately one seven-hundredth and one four-hundredth of those of S1 and N-Ac-Cys, respectively. Fluorimetric studies using BIPM revealed that S2 in the buried state was exposed upon adding ATP; this was compensated by the burying of some other thiol group(s) (Sp). Non-linearity of the Arrhenius plots of the reaction rate of S2 suggested that the S2 region of myosin had different conformations at high and low temperatures, the transition temperature being 10--15degrees. This non-linearity completely disappeared in the presence of Mg2+-ATP. On the other hand, Arrhenius plots for the thiols reactive to BIPM did not show non-linearity in the presence or absence of ATP.
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PMID:Thiols of myosin. IV. "Abnormal" reactivity of S1 thiol and the conformational changes around S2 thiol. 0 75

The histochemical activities of succinic dehydrogenase (SDH) and Ca++-activated ATPase (pHs 7.4 and 9.4) were studied in the larval tail musculature of Rana japonica, Rana catesbeiana and Rana ornativentris. The ATPase reaction product was detected by both light and electron microscopy. 'Red' and 'white' muscle fibres, as distinguished by SDH, showed high and low Ca++-ATPase reaction, respectively, at pHs 7.4, 9.4 and following preincubation in cold K2-EDTA solution. The ultrastructural investigation of Ca++-ATPase reaction at pH 7.4 by the Ca++-citrophosphate technique demonstrated electron-dense reaction product in association with A, I and 'Z' bands, intermyofibrillar (SR) compartment and the mitochondrial inner chamber. However, Pb++ precipitation technique demonstrated Mg++-activated myosin ATPase activity at pH 9.2 ultrastructurally. The present histochemical data suggest that the anuran larval tail 'red' muscle fibres are possible 'slow,' and emphasize a possible lack of correlation between the speed of contraction with their ATPase activity. Moreover, 'red' muscle fibres of the anuran tai- musculature are not equivalent to 'Type I' fibres of higher chordates.
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PMID:Light and electron microscopic study of adenosine triphosphatase activity of anuran tadpole musculature. 2 41

The rate of enzymic reaction of ATP, ITP, GTP with myosin is studied in the presence of potassiu, ammonium and calcium ions in H2O--D2O solutions. There is no kinetic isotope effect of ITPase and GTPase reaction in the neutral pH region (VHVD = 1). The value VH/VD for the ATPase reaction in the pH range from 6.5 to 8.5 with all cations studied varies from 1.05 to 1.26. Such changes of myosin enzymic activity in D2O infer that small changes in the interaction of subunits is not the decisive one in the regulation of myosin ATPase. The equality of isotope effects in potassium salts and ammonium solution suggests that a specific effect of ammonium ion as a proton donor affects the ATPase reaction of myosin. The relationship between the value of isotope effect and D2O concentration in solution in non-linear. The shape of concentration curve suggests essential conformational changes of myosin during ATP hydrolysis.
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PMID:[Enzyme activity of myosin activated by different cations in a mixed H2O--D2O solvent]. 3 22

A myosin was isolated from the clonal rat glial cell strain C-6 and compared with rat skeletal muscle myosin. After cell extracts were subjected to gel filtration chromatography in the presence of KI and magnesium pyrophosphate the C-6 myosin was rapidly purified by a procedure similar to that used for skeletal muscle myosin. The C-6 myosin resembles muscle myosin both physically and enzymatically. It contains heavy chains of 200,000 daltons and two classes of light chains of 17,000 and 19,000 daltons in approximately equal molar ratios. This myosin forms bipolar thick filaments in 0.1 M KCl and binds reversibly to skeletal muscle F-actin, the binding being inhibited by MgATP. Skeletal muscle F-actin stimulates the C-6 myosin adenosine triphosphatase 2- to 3-fold in the presence of KCl and Mg2+. The action activation of muscle myosin ATPase at low ionic strength is 10-fold greater than that of C-6 myosin. Ca2+ and EDTA stimulated the ATPase activities of both enzymes. When assayed in the presence of 0.6 M KCl and 1 mM EDTA the skeletal muscle myocin ATPase demonstrates substrate saturation while the C-6 myosin enzyme activity is stimulated by ATP concentrations above 2.5 mM.
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PMID:Purification and characterization of myosin from the clonal rat glial cell strain C-6. 12 31

The ATPase activity of myosin and contraction time in extensor digitorum longus muscle, soleus muscle and cardiac muscle was compared in mammals differing in size. It was shown that the myosin ATPase activity of homologous muscles decreases and contraction time increases with increasing size of animals. The rate of tryptic digestion of myosin, the electrophoretic pattern of light chains of myosin and the effect of p-chloromercuribenzoate on ATPase activity of myosin were also studied. All these three myosin properties are very characteristic when the myosin from a fast muscle is compared with the myosin from a slow muscle of the same animal, but no relationship between these three myosin properties and ATPase activity of myosin was found, when homologous muscles of various mammals were compared.
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PMID:Myosin from fast and slow skeletal and cardiac muscles of mammals of different size. 12 84

The cyclic peptide phalloidin, one of the toxic components of Amanita phalloides prevented the drop of viscosity of F-actin solutions after the addition of 0.6 M KI and inhibited the ATP splitting of F-actin during sonic vibration. The data concerning ATP splitting are consistent with the assumption (a) that only 1 out of every 3 actin units of the filaments needs to be combined with phalloidin in order to suppress the contribution of these 3 actins to the ATPase activity of the filament and (b) that all actin units of the filaments can combine with phalloidin with a very high affinity. -halloidin did not only stabilize the actin-actin bonds in the F-actin structure but it also increased the rate of polymerization of G-actin to F-actin. The ability of F-actin to activate myosin ATPase was not affected by phalloidin. The tropomyosin-troponin complex did not prevent the stabilizing effect of phalloidin on the F-actin structure.
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PMID:Interaction of actin with phalloidin: polymerization and stabilization of F-actin. 12 84

The slow anterior latissimus dorsi (ALD) muscles of newly hatched chickens were transposed and cross0innervated by the mixed, predominantly fast superior brachialis nerve, and investigated 2 to 15 months after the operation. Two months after the operation, myosin ATPase activity of the cross-innervated ALD muscles was still as low as in the control ALD, although the ultrastructure and the histochemical ATPase activity already showed a mixed fibre-type pattern with a predominance of fast -type fibres around the site of nerve implantation. The change of myosin properties of thw whole cross-innervated ALD did not occur until the third month after the operation. At that time, the myosin ATPase activity increased about 2.5 times and light chains of myosin of the fast type appeared in the electrophoretic pattern. The myosin ATPase activity attained 62% of the activity found in the control fast posterior latissimus dorsi muscles at three months; subsequently it remained at about this level reaching 68% 18 months after the operation. The results indicate that approximately two thirds of the cross-innervated ALD muscle fibres became changed towards the fast type under neural influence, whereas about one third remained slow, being re-innervated by the slow-type motor fibres of the implanted nerve.
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PMID:The onset and progress of transformation of avian slow into fast muscles under neural influence. 12 64

G-actin has been nitrated with tetranitromethane in conditions that lead to the modification of one tyrosine residue. The reactive residue was found by earlier workers to be Tyr-69. The nitrated actin is conformationally similar to native G-actin, as judged by sedimentation velocity and circular dichroism analysis. A small proportion only is in the form of covalently linked dimers and trimers. The nitrated G-actin will polymerise to form filaments, indistinguishable in the electron microscope from those of native F-actin, but the polymerisation process is slower. Reduction of the nitrophenol group to the corresponding aminophenol leaves the properties of the protein in respect of polymerisation unchanged. When a dansyl group is introduced at the same point, however, the ability of the actin to polymerise is lost. The nitrated actin and its reduced counterpart will also bind heavy meromyosin, and the characteristic arrowhead formation of the bound molecules along the filaments can be seen in the electron microscope. Neither of the modified F-actins, however, significantly activates or inhibits the myosin ATPase activity. The fluorescence of nitrated actin is strongly quenched through the presence of the nitrophenol chromophore. In soluble complexes with heavy meromyosin the fluorescence is indistinguishable from the sum of the separate contributions of the two protein components. There is thus no measurable excitation transfer between any tryptophan residues on the myosin heads, such as that inferred to be present in the ATPase site, and the nitrotyrosine in position 69 of the actin sequence. Implications of this observation are considered in relation to the different interaction sites in myosin and in actin. The activation of heavy meromyosin ATPase by copolymers containing actin and nitroactin in different proportions has been measured, and is not proportional to the fraction of native actin. The results are consistent with the view that the function of actomyosin depends on the interaction of the myosin heads with more than one actin subunit.
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PMID:Effects of specific chemical modification of actin. 12 59

Mild pulmonic stenosis was performed in dogs to evaluate the effect of systolic pressures overloading on the activity and subunits of myosin in the early hypertrophied right ventricle. Three weeks following pulmonary constriction, six hypertrophied dogs were sacrificed and compared to six sham-operated dogs which served as controls. In the right ventricular free wall of hypertrophied right ventricles (HRV), the heart/body weight was 46% greater than that of normal right ventricles (NRV) (p less than 0.01). Myosin ATPase activity (Vmax values) in mumoles phosphate/mg/min, was elevated significantly in the stressed ventricle for both K+ and Ca++ activity in hypertrophied right ventricles. Associated with the increase in myosin activity, there was an increase in proportion of heavy to light chains in myosin from HRV. There were approximately 2 moles of myosin light chains per mole of myosin heavy chains in NRV and approximately 1 mole of myosin light chains per mole of myosin heavy chains in HRV. The proportion of light chain C1 to C2, did not change in myosin from NRV and HRV. Of the C1 light chains, according to two-dimensional gel electrophoresis, there was less C1d as compared to C1c in HRV as compared to NRV. Thus K+- and Ca++- activated myosin is elevated in early canine HRV by pressure overload. It is suggested taht the augmented myosin activity is due to a reduction of light chain inhibition of myosin ATPase activity, which appears to result from the slower turnover rate of myosin light chains relative to heavy chains. Furthermore, when myosin light chains are added to hypertrophied right ventricular myosin, the ATPase activity is lowered.
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PMID:Modulation of myosin in right ventricular hypertrophy. 12 38


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