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)

1. Tropomyosin, one of the regulatory proteins in muscle contraction, was prepared from chickens, rabbits, frogs, shrimps, and shellfish, and conserved characteristics were studied using an enzymological technique. 2. All tropomyosins tested, irrespective of their sources, were found to have the ability to mediate the inhibitory activity of rabbit troponin toward rabbit Mg2+-activated actomyosin ATPase (Mg2+-ATPase) activity in the absence of Ca2+ ions. 3. The effect of tropomyosin on the Mg2+-ATPase activity in the presence of Ca2+ ions varied, depending on the source, and this variation appeared to reflect the evolutionary course of this protein. 4. Tropomyosin from shellfish adductor muscle had the ability to bind to rabbit skeletal muscle troponin and actin. This ability is also considered to be a basic characteristic of tropomyosin which has been conserved during evolution.
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PMID:The functional characteristics conserved in tropomyosins. 14 70

Ca2+ regulation of molluscan actomyosin adenosine triphosphatase is known to be associated with the myosin molecule. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, however, also suggests the possible presence of troponin, a thin-filament-linked Ca2+-regulatory complex. In the present study, scallop troponin and tropomyosin were prepared and complexed with rabbit actin; the resulting synthetic thin filaments form a Ca2+-dependent actomyosin adenosine triphosphatase with Ca2+-insensitive rabbit myosin, indicating that the troponin in scallops is potentially functional. Scallop troponin I was isolated and mixed with chicken troponin C and troponin T, forming a functional hybrid troponin complex, indicating that scallop and vertebrate troponins may act by a common mechanism. Densitometry of sodium dodecyl sulphate/polyacrylamide gels reveals that in synthetic thin filaments there are larger amounts of troponin than are present in native thin filaments. Amounts present in the intact muscle were not determined.
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PMID:Troponin-like proteins from muscles of the scallop, Aequipecten irradians. 14 88

Steady and uniform streamings (SUS) of HMM solutions were set up in the presence of Mg-ATP in a circular slit, on both side-walls of which a Millipore filter was fixed; F-actin filaments from rabbit skeletal muscle were bound onto the Millipore filter by cyanogen bromide in the flow. The direction of the SUS was specificially determined by that of the flow during the fixing of F-actin and was independent of the direction of the initial velocity applied externally to the HMM solutions. The SUS continued for about 90 min with a velocity of about 20 mum/s at 20 degrees C. There was a strong correlation between the acto-HMM ATPase activity and the velocity of SUS when the salt concentration was varied. Moreover, this was also the case when the ATPase activity was controlled by Ca2+, when native tropomyosin was bound to F-actin in the circular slit. Careful examination led to the conclusions that F-actin filaments are fixed on the Millipore filter with a specific polarity and that a chemo-mechanical system had been successfully reconstituted in our "stream cells," in which chemical energy from ATP is converted to the mechanical energy of streaming.
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PMID:Studies of the chemo-mechanical conversion in artificially produced streamings. I. Reconstruction of a chemo-mechanical system from acto-HMM of rabbit skeletal muscle. 15 79

An inhibitory protein for Mg2+-activated actomyosin ATPase from rabbit skeletal muscle was prepared from frozen chicken gizzard and purified by DEAE-Sephadex chromatography and gel filtration. 2. The inhibition by this protein was released by the addition of skeletal muscle troponin C and was independent of gizzard tropomyosin. 3. Localization of the inhibitory protein in gizzard muscle tissue and gizzard thin filaments was demonstrated by immunohistological techniques and immunodiffusion tests.
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PMID:Isolation and localization from chicken gizzard of an inhibitory protein for Mg2+-activated skeletal muscle actomyosin ATPase. 15 12

Modulator-deficient myosin light-chain kinase from rabbit skeletal muscle was purified by modulator protein-Sepharose 4B affinity chromatography. The purified protein showed a single band (MW 80,000) on polyacrylamide gel electrophoresis in sodium dodecyl sulfate, and it exists as a monomer in the native state as determined by gel filtration. The modulator-deficient myosin light-chain kinase (MW 80,000), modulator protein (MW 16,500) and Ca2+ were essential for the kinase activity. The half-maximal activity of the kinase in the presence of excess modulator protein with 10 mM MgCl2 was at pCa 5.1, where full activity of actomyosin-ATPase is observed in the presence of the troponin--tropomyosin system. Assuming a rapid equilibrium between myosin light-chain kinase and two substrates, ATP and g2 light-chain, Km values for ATP and g2 light chain were evaluated as 0.28 mM and 0.024 mM, respectively. Vm/e was 5.7 s-1.
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PMID:Purification of modulator-deficient myosin light-chain kinase by modulator protein-Sepharose affinity chromatography. 15 46

alpha-Actinin isolated from bovine brain migrated on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis like muscle alpha-actinin with an apparent mol.wt. of 100000 and cross-reacted with antibodies to muscle alpha-actinin. Brain alpha-actinin modulated actin-myosin Mg2+-activated adenosine triphosphatase activity and, when bound by polystyrene particles, was found to bind muscle actin and tropomyosin from solution. Brain alpha-actinin, in conjunction with the other components of the contractile and relaxing complex, may play a role in the release of neurotransmitters from synaptic vesicles.
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PMID:Isolation and properties of brain alpha-actinin. 15 45

The Ca-regulatory system in squid mantle muscle was studied. The findings were as follows. (a) Squid mantle myosin B (squid myosin B) was Ca-sensitive, and its Ca-sensitivity was unaffected by addition of a large amount of rabbit skeletal myosin (skeletal myosin) or rabbit skeletal F-actin (skeletal F-actin). (b) Squid myosin was prepared from the mantle muscle. It showed a heavy chain component and two light chain components in the SDS-gel electrophoretic pattern: the molecular weights of the latter two were 17,000 and 15,000. Actomyosin reconstituted from squid myosin and skeletal (or squid) actin showed Ca-sensitivity in superprecipitation and Mg-ATPase assays. EDTA- treatment had no effect on the Ca-sensitivity of squid myosin. (c) Squid mantle actin (squid actin) was prepared by the method of Spudich and Watt. Hybrid actomyosin reconstituted by using the pure squid actin preparation with skeletal myosin showed no Ca-sensitivity in Mg-ATPase assay, whereas that reconstituted using crude squid actin showed marked Ca-sensitivity. The crude squid actin contained four protein components which were capable of associating with F-actin in 0.1 M KCl, 1 mM MgCl2 and 20 mM Tris-maleate (pH7.5). (d) Native tropomyosin was prepared from squid mantle muscle, and it conferred Ca-sensitivity on skeletal actomyosin as well as on a hybrid actomyosin reconstituted from squid actin and skeletal myosin. (e) Squid native tropomyosin was separated into troponin and tropomyosin fractions by placing it in 0.4 M LiCl at pH 4.7. The troponin fraction was further purified by DEAE-cellulose chromatography. Squid troponin thus obtained was different in mobility from rabbit skeletal or carp dorsal troponin; three bands of squid troponin corresponded to molecular weights of 52,000, 28,000, and 24,000 daltons. It could confer Ca-sensitivity in the presence of tropomyosin on skeletal actomyosin as well as on a hybrid reconstituted from squid actin and skeletal myosin. (f) Squid myosin B, and two hybrid actomyosins were compared as regards Ca and Sr requirements for their Mg-ATPase activities. The myosin-linked regulatory system rather than the thin-filament-linked regulatory system was predominant in squid myosin B. Squid myosin B required higher Ca2+ and Sr2+ concentrations for Mg-ATPase activity; half-maximal activation of Mg-ATPase was obtained at 0.8 micron Ca2+ and 28 micron Sr2+ with skeletal myosin B, and at 2.5 micron Ca2+ and 140 micron Sr2+ with squid myosin B.
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PMID:Two calcium regulation systems in squid (Ommastrephes sloani pacificus) muscle. Preparation of calcium-sensitive myosin and troponin-tropomyosin. 15 2

A method was developed to obtain a preparation of chicken gizzard heavy meromyosin (HMM) that retains the two light-chain components of parent myosin: the 20,000-dalton and 17,000-dalton light-chains. The HMM preparation was also shown to retain two characteristics of the ATPase activity of the parent myosin: the characteristic effect of phosphorylation of the 20,000-dalton light-chain component on the ATPase activity, and the characteristic dependence of the ATPase activity on the KCl concentration. 1. Two distinct stages were observed in the Mg-ATPase reaction catalyzed by gizzard HMM and rabbit skeletal actin in the presence of gizzard "native" tropomyosin (NTM) and Ca2+ ions: an early lag phase, in which the reaction rate gradually increased, and a subsequent steady state, in which the reaction proceeded at a high, constant rate. Urea-gel electrophoresis revealed that the 20,000-dalton light-chain component was gradually phosphorylated in the lag phase, and was fully phosphorylated in the steady state. It was also observed that addition of EGTA (to remove Ca2+ ions) at various times in the lag phase caused neither a further increase nor a decrease in the reaction rate, and that addition of EGTA in the steady state caused no change in the reaction rate. These observations imply that the ATPase activity increased as the amount of phosphorylated 20,000-dalton light-chain component increased, and also that Mg-ATPase of acto-phosphorylated HMM was no longer calcium-sensitive. 2. The Mg-ATPase activity of HMM in the presence of gizzard NTM and Ca2+ ions or EGTA was studied as a function of the concentration of rabbit skeletal actin. The maximal activity (Vmax) and the apparent affinity constant of acto-HMM (KA) were thus estimated from the double-reciprocal plot of Eisenberg-Moos: the Vmax and KA values for phosphorylated HMM (in the presence of Ca2+ ions) were 5 S(-1) and 5.5 mg/ml actin, respectively, and the Vmax value for unphosphorylated HMM (in the presence of EGTA) was 0.3 S(-1), assuming that the KA value with unphosphorylated HMM is equal to that with phosphorylated HMM.
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PMID:Chicken gizzard heavy meromyosin that retains the two light-chain components, including a phosphorylatable one. 15 13

A bovine cardiac actin-tropomyosin-troponin complex was phosphorylated in the presence of [gamma-32P]ATP, Mg2+, adenosine 3',5'-monophosphate (cyclic AMP), and bovine cardiac cyclic-AMP-dependent protein kinase. Approximately 81% of the [32P]phosphate incorporated was identified as phosphoserine and phosphothreonine. Gel electrophoresis studies showed that 55% of the [32P]phosphate was associated with the inhibitory component of troponin (Tn-I) and 24% with a protein resembling the tropomyosin-binding component of troponin in the actin complex, respectively. The phosphorylation of Tn-I in the actin complex was inhibited 30% when Ca2+ was increased from 0.1 to 50 muM, but phosphorylation of other components was not affected by increasing Ca2+ concentration. Half-maximal calcium activation of the ATPase activity of reconstituted actomyosins made with the [32P]phosphorylated cardiac actin complex and cardiac myosin was shifted to Ca2+ values higher than those of actomyosins made with the nonphosphorylated actin complex.
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PMID:Phosphorylation of a bovine cardiac actin complex. 15 2

A 20-residue peptide analog of the actomyosin ATPase inhibitory region of rabbit skeletal troponin I (Tn-I) has been synthesized by the solid phase method. The analog exhibited biological activity similar to both Tn-I and a 21-residue cyanogen bromide fragment of Tn-I. At ionic strengths where the inhibition of the actomyosin ATPase due to tropomyosin alone is low, the synthetic peptide in the presence of tropomyosin inhibits 90% of the original ATPase activity. In the absence of tropomyosin, the inhibition due to the peptide is much reduced. In contrast, salmine, a basic protein also known to inhibit the actomyosin ATPase, shows less inhibition in the presence of tropomyosin than it does in its absence. Gel electrophoresis data showed that the enhancement of the analog's inhibition by tropomyosin may be related to the analog's promotion of tropomyosin binding to F-actin similar to that reported for Tn-I and that the reduction of salmine inhibition by tropomyosin may be due to the binding of salmine by tropomyosin. At ionic strengths where binding and inhibition of tropomyosin is significant, the analog enhanced inhibition in a manner similar to that reported for whole Tn-I.
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PMID:Synthesis and biological activity of an icosapeptide analog of the actomyosin ATPase inhibitory region of troponin I. 15 93


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