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)

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

Whereas dissociation of rabbit skeletal muscle myosin light chains occurs at an increased temperature (25 degrees) and in the absence of divalent cations, reassociation of the myosin oligomer requires a low temperature (4 degrees C) and the presence of divalent cations, thus resulting in the original light to heavy chain stoichiometry. With a 5-10 per cent release of alkali light chains, LC1 and LC3, and a 50 per cent dissociation of the Ca2+ binding light chain, LC2, there is no significant decrease in myosin ATPase activity irrespective of the cation activator, however, there is an approximate 15-20 per cent decrease in actomyosin ATPase activity. With reassociation of the myosin oligomer, actomyosin ATPase activity is partially restored as well as the original number of Ca2+ binding sites.
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PMID:Dissociation and reassociation of rabbit skeletal muscle myosin. 16 9

Myosin isoforms and their light and heavy chains subunits were studied in the white lateral muscle of the eel during the post metamorphic development, in relation with the myosin ATPase profile. At elver stage VI A1 the myosin isoforms pattern was characterized by at least two isoforms, FM3 and FM2. The fast isomyosin type 1 (FM1) appeared during subsequent development. It increased progressively in correlation with the increase in the level of the light chain LC3f. FM1 became predominant at stage VI A4. At the elver stage VI A1, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed at least two heavy chains, namely type II-1 and II-2. The type II-1 heavy chain disappeared in the yellow eel white muscle, and V8-protease peptide map showed the appearance of a minor heavy chain type II-3 as early as stage VI B. Comparison of myosin heavy chains and myosin isoforms patterns showed the comigration of different myosin isoforms during white muscle development. The myosin ATPase profile was characterized by a uniform pattern as far as stage VI A4. A mosaic aspect in white muscle was observed as early as stage VI B, showing the appearance of small acid labile fibers. This observation suggests that the type II-3 heavy chain is specific to the small fibers.
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PMID:White muscle differentiation in the eel (Anguilla anguilla L.): changes in the myosin isoforms pattern and ATPase profile during post-metamorphic development. 153 45

Hypertrophy of the urinary bladder was produced in rabbit by partial ligation of the urethra. Electrophoresis of the bladder smooth muscle myosin on highly porous (3.5-7% gradient) SDS-polyacrylamide gel revealed two heavy chain isoforms, SM-1 and SM-2 with approximate molecular weights of 204,000 and 200,000, respectively. The ratio of the SM-2 to SM-1 heavy chain is 3:1 for myosin isolated from normal bladder smooth muscle, and this ratio changes to about 1:1 in hypertrophied bladder. Despite a change in the ratio of SM-2 to SM-1, the myosin ATPase and the actin-activated ATPase activities are not altered in response to hypertrophy.
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PMID:Smooth muscle myosin isoform distribution and myosin ATPase in hypertrophied urinary bladder. 153 95

Scallop adductor myosin is regulated by its subunits; the regulatory light chain (R-LC) and essential light chain (E-LC). Myosin light chains suppress muscle activity in the absence of calcium and are responsible for relaxation. The binding of Ca2+ to the myosin triggers contraction by releasing the inhibition imposed on myosin by the light chains. To map the functional domains of the R-LC, we have carried out mutagenesis followed by bacterial expression. Both wild-type and mutant proteins were hybridized to scallop myosin heavy chain/E-LC to map the regions of the light chain that are responsible for the binding to the myosin heavy chain/E-LC, for restoring the specific calcium-binding site, and controlling the myosin ATPase activity. The R-LC is expressed in Escherichia coli using the pKK223-3 (Pharmacia) expression vector and has been purified to greater than 90% purity. E. coli-expressed wild-type R-LC differs from the native R-LC by having the initiating methionine residue and an unblocked NH2 terminus. The wild-type R-LC restores Ca2+ binding and Ca2+ sensitivity when hybridized to scallop myosin. A point mutation of the sixth Ca2(+)-liganding position of domain I (Asp39----Ala39) results in a R-LC that binds more weakly to the heavy chain/E-LC and restores the specific Ca2(+)-binding site but not regulation of the actin-activated Mg2+ ATPase. A second mutation was produced by substituting the last 11 residues of the COOH terminus with 15 different residues. This mutant restores the specific Ca2(+)-binding site, but does not restore Ca2+ regulation to the actin-activated ATPase activity. Several other point mutations do not alter light chain function. The experiments directly establish that the divalent cation-binding site of domain I is functionally distinct from the specific Ca2(+)-binding site. The results indicate that an intact domain I and the COOH terminus are required to suppress the myosin ATPase activity. The fact that the domain I mutation and the COOH-terminal mutation disrupt regulation but do not affect Ca2(+)-binding indicates that these two aspects of regulation are separable and, therefore, the R-LC has distinct functional regions.
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PMID:Regulation of scallop myosin by mutant regulatory light chains. 214 99

The heptapeptide Ile-Arg-Ile-Cys-Arg-Lys-Gly-OEt is the analog of the S-site, one of the actin-binding sites in myosin [Suzuki et al. (1987) J. Biol. Chem. 262, 11410-11412]. Various substituted heptapeptides were synthesized, and the dissociation constants of each acto-heptapeptide complex was measured. Comparison of the dissociation constants indicated that the hydrophobic side chain of Ile-1 was critical for the binding with F-actin, but not that of Ile-3. The positive charge and the side chain length of Arg-2 were also important. The presence of a sulfur atom in the Cys-4 was also necessary. The affinity of the N-terminal Ile-Arg-Ile part for F-actin was influenced by the kind of residues in the C-terminal tetrapeptide part. Based on these results, the side chains of Ile(702), Arg(703), and Cys(SH1)(705) in myosin subfragment-1 heavy chain were assigned to be critical for the binding with F-actin. The amino acid sequence of S-1 heavy chain containing these critical residues for the S-site from residue number 700 to 717 can be predicted as an analogue of the segment B of the ATP-binding site [Walker et al. (1982) EMBO J. 1, 945-951]. The actin-binding S-site possibly shares a part of the ATP-binding site in myosin. We discuss the possibility that the S-site is an inhibitory site of myosin ATPase and the so-called actin-activation of myosin ATPase is a deinhibition induced by transient binding of F-actin to the S-site.
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PMID:Roles of the amino acid side chains in the actin-binding S-site of myosin heavy chain. 214 38

Monoclonal antibodies against gizzard smooth muscle myosin were generated and characterized. One of these antibodies, designated MM-2, recognized the 17-kDa light chain and modulated the ATPase activities and hydrodynamic properties of smooth muscle myosin. Rotary shadowing electron microscopy showed that MM-2 binds 51 (+/- 25) A from the head-rod junction. The depression of Ca2+- and Mg2+-ATPase activities of myosin and Ca2+-ATPase activity of heavy meromyosin at low KCl concentration were abolished by MM-2. Viscosity measurement indicated that MM-2 inhibits the transition of 6 S myosin to 10 S myosin. While the rate of the production of subfragment-1 by papain proteolysis of 6 S myosin was inhibited by MM-2, the rate of proteolysis of the heavy chain of 10 S myosin was enhanced by MM-2 and reached the same rate as that of 6 S myosin plus MM-2. These results suggest that MM-2 inhibits the formation of 10 S myosin by binding to the 17-kDa light chain which is localized at the head-neck region of the myosin molecule. MM-2 increased the Vmax of actin-activated Mg2+-ATPase activities of both dephosphorylated myosin and dephosphorylated heavy meromyosin about 10- and 20-fold, respectively. MM-2 also activated the actin-activated Mg2+-ATPase activity of phosphorylated myosin at a low MgCl2 concentration and thus abolished the Mg2+-dependence of acto phosphorylated myosin ATPase activity. These results suggest that MM-2 inhibits the formation of 10 S myosin, and this results in the activation of actin-activated Mg2+-ATPase activity even in the absence of phosphorylation.
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PMID:Inhibition of conformational change in smooth muscle myosin by a monoclonal antibody against the 17-kDa light chain. 246 45

The heavy chain of myosin from rabbit skeletal muscle can be cleaved at three sites by irradiation with near-ultraviolet light in the presence of 0.1-1.0 mM vanadate. The sigmoidal dependence upon vanadate concentration, with half-maximal rate occurring at about 0.5 mM vanadate and a sigmoidicity of 2.7, is consistent with the chromophore responsible for cleavage being oligomeric vanadate. Cleavage occurs at two sites located within the head region of the molecule, 23 kDa and 75 kDa from the NH2-terminus; these sites are cleaved equally well in heavy meromyosin and subfragment 1. In the presence of 1 mM vanadate, the half-times for cleavage of the 23-kDa and 75-kDa sites are about 15 and 10 min, respectively. The rate of cleavage at both these sites is retarded 2-3-fold by the presence of greater than 10 microM MgATP. The third photocleavage site is located about 5-10 kDa from the COOH terminus of the intact heavy chain, and cleaves equally well in the isolated rod and in light meromyosin. Cleavage at this site occurs with a half-time of 138 min, and its rate is unaffected by the presence of MgATP. The vanadate-mediated cleavage of the heavy chains is accompanied by characteristic changes in the myosin ATPase properties, with the Ca2+, Mg2+ and actin-activated Mg2+ ATPases becoming elevated, whereas the K+/EDTA ATPase becomes inactivated. The sites of photocleavage in the myosin heavy chain might be associated with sites of phosphate binding.
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PMID:Vanadate-mediated photocleavage of rabbit skeletal myosin. 253 8

The pathogenesis of reduced systolic left ventricular function in dilated cardiomyopathy is yet unclear. To analyze a possible involvement of contractile protein, function and structure of left ventricular myofibrils were examined in hearts of patients with advanced cardiomyopathy undergoing heart transplantation and in normal control hearts (from renal transplant donors). Myosin and actin content of the left ventricular myocardium was slightly reduced in cardiomyopathic hearts. Myofibrillar polypeptide composition was determined using two-dimensional electrophoresis and immunoblotting. No differences in constituting polypeptides were apparent, including Z-line proteins and proteins of the endosarcomeric lattice. M-line-bound creatine kinase was identical in both groups. Further, basal and maximal myofibrillar adenosine triphosphatase (ATPase) activities were unaltered in dilated cardiomyopathy. The structure of purified myosin was identical in both groups by the following criteria: electrophoretic mobility of native myosin, identical pattern of light chains after isoelectric focusing, identical cleavage peptides of myosin's heavy chain, and identical patterns after immunoblotting of heavy chain cleavage peptides using polyclonal antibodies generated against myosin from normal and cardiomyopathic ventricles. Ca2+-activated, K+-EDTA-activated and actin-activated myosin ATPase activities were identical in control and cardiomyopathic hearts. A structural alteration or functional defect of myofibrils does not seem to be primarily involved in the pathogenesis of reduced myocardial contractility in dilated cardiomyopathy.
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PMID:Structure and function of contractile proteins in human dilated cardiomyopathy. 258 58

Myosin (opaque myosin) isolated from the opaque portion of scallop smooth muscle, a catch muscle, was subjected to limited digestion by trypsin during the steady-state ATPase reaction. The 200-kDa heavy chain of opaque myosin was cleaved into 125- and 74-kDa fragments. The proteolytic rate in the absence of Ca2+ was lower than that in the presence of Ca2+, and was similar to that in the presence of ADP and absence of Ca2+. The results suggest that the steady-state intermediate of opaque myosin ATPase in the absence of Ca2+ is EADP, which is consistent with the previous results based on the difference UV-absorption spectrum (Takahashi, M., Sohma, H., & Morita, F. (1988) J. Biochem. 104, 102-107). In the presence of F-actin, the proteolytic rates were decreased, but the digestive patterns by trypsin were similar to those of myosin alone. Even in the presence of F-actin, the proteolytic rate during the ATPase reaction in the absence of Ca2+ was lower than that in the presence of Ca2+, and was similar to that in the presence of ADP and absence of Ca2+. In addition, there was another trypsin-susceptible site which is probably located at 18 kDa from the N-terminal of the heavy chain. The site in the absence of Ca2+ was hardly cleaved when ATP or ADP was present. Similar tendencies were observed even in the presence of F-actin. These findings suggest that the intermediate of opaque myosin ATPase at the steady state in the absence of Ca2+ is EADP even in the presence of F-actin.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Myosin may stay in EADP species during the catch contraction in scallop smooth muscle. 261 94


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