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 fiber type composition of two fast muscles of the chicken, namely, adductor superficialis (AS) and pectoralis major (PM) was examined by the histochemical myosin ATPase staining and immunochemical techniques using monoclonal antibodies (McAbs). Two new McAbs produced against the myosin of the anterior latissimus dorsi (ALD) muscle of the chicken and named ALD-122 and ALD-83 were characterized to be specific for myosin heavy chain (MHC) and for myosin light chain-1 respectively. They were used in conjunction with previously reported McAbs specific for slow MHC (ALD-47), fast MHC (MF-14) and fast light chain-2 (MF-5). By the histochemical ATPase test most muscle fibers of AS and PM muscles reacted as IIA and IIB respectively. By immunofluorescent staining with the anti-MHC McAbs, ALD-122 and MF-14, the fibers of AS muscle showed remarkable heterogeneity whereas PM muscle fibers reacted uniformly. Differences in the myosin light chain composition of AS and PM muscles were also found by SDS-gel electrophoresis and immunoblot analysis with the anti-light chain McAb, ALD-83. The study clearly indicated that the histochemically homogenous (type IIA) AS muscle is composed of several subpopulations of fibers which differ in their myosin composition and that this heterogeneity of the muscle is not simply due to presence of variable amounts of slow myosin in its fibers.
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PMID:Heterogeneity of fast-oxidative muscle fibers of chicken demonstrated by anti-myosin monoclonal antibodies. 273 24

An antibody obtained by immunizing a rabbit with purified bovine brain myosin was found to react with the tail portion of the myosin heavy chain. An Fab fragment obtained by limited papain digestion of the antibody was allowed to bind to brain myosin, and the complex of the Fab fragment and brain myosin (Fab-myosin) was isolated. On examination of the rotary-shadowed Fab-myosin by electron microscopy, most of the Fab fragment was located on the middle to C-terminal regions of the tails of the myosin molecules. The solubility of Fab-myosin in low salt solutions was higher than that of control brain myosin. Fab-myosin was found to form small irregular aggregates in low salt solutions instead of regular bipolar filaments, and the relative population of the monomeric form of myosin molecules observed for the Fab-myosin was much larger than that observed for the control myosin. The actin-activated Mg2+-ATPase activity of Fab-myosin was stimulated two- to threefold by phosphorylation of the light chains with myosin light chain kinase, as observed for the control brain myosin. Furthermore, the levels of the ATPase activity of the phosphorylated and dephosphorylated Fab-myosins were similar to those of the phosphorylated and dephosphorylated control myosins, respectively. The superprecipitation activity of Fab-myosin was also highly dependent on phosphorylation of the light chains. Although control brain myosin formed a large superprecipitate network which contracted to a dense particle, Fab-myosin generated only numerous tiny superprecipitates under the same conditions. From these results it was deduced that a regular filamentous state of brain myosin was not prerequisite for its actin-activated Mg2+-ATPase and superprecipitation activities but was indispensable for the formation of a large and well contractible superprecipitate.
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PMID:Physical, enzymatic, and contractile properties of brain myosin with anti-brain myosin Fab fragment bound on its tail. 275 76

Contraction of the hypothyroid heart is characterized by delayed diastolic relaxation and decreased velocity of systolic contraction. In order to determine if these alterations could be mediated by the changes in the mRNA coding for the Ca++ ATPase of the sarcoplasmic reticulum and alterations of the mRNAs coding for myosin heavy chain (MHC) alpha and beta, the levels of these specific mRNAs were quantitated using a Northern blotting technique. We find that the Ca++ ATPase mRNA was 3-fold lower in hypothyroid hearts. After T3 administration to hypothyroid rats, Ca++ ATPase mRNA increased to 66% of control levels within 2 hrs and to 100% of control levels 5 hrs after T3 administration. In the hypothyroid heart, MHC beta mRNA was the predominant message with MHC alpha mRNA barely detectable. Administration of 2 mg of T3 led to a significant increase in MHC alpha mRNA levels first detectable 2 hrs after T3 administration. Twenty-four hrs after T3 administration, MHC alpha mRNA levels had normalized. The results of these studies indicate that thyroid hormone mediates significant alterations in the level of the mRNA coding for the Ca++ ATPase of the sarcoplasmic reticulum and of the mRNAs coding for MHC alpha and beta. Changes in the level of these specific mRNAs resulting in lower levels of the corresponding proteins may explain the delayed diastolic relaxation and the decreased velocity of contraction of the hypothyroid heart.
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PMID:Thyroid hormone induced changes in cardiac proteins and mRNAs. 289 58

Triton X-100 residues (cytoskeletons) of human platelets were prepared in the presence of various concentrations of free calcium (Ca2+), and the polypeptide composition and ATPase activity were examined. Triton residues prepared in the presence of Ca2+ concentrations below 2 X 10(-7) M were composed primarily of polypeptides with an apparent molecular mass of 43 (actin), 105 (alpha-actinin-like protein) and 250 (actin-binding protein) kDa and showed low K+-EDTA-ATPase activity. When Triton residues were prepared at Ca2+ above 5 X 10(-7) M, a 200 kDa polypeptide (myosin heavy chain) and K+-EDTA-ATPase activity increased markedly, but actin-binding protein and alpha-actinin-like protein decreased. When N-(N-(L-3-trans-carboxyoxirane-2-carbonyl)-L-leucyl)agmatine, an inhibitor for Ca2+-dependent proteinase, was added to Triton lysis buffer containing high Ca2+, polypeptides of 250, 235 and 105 kDa remained associated with the residues. Under electron microscopic analysis, the treatment of platelets with Triton X-100 at low Ca2+ showed a network of microfilaments. When platelets were treated with high Ca2+, the microfilaments were disrupted and a few thick filaments and many granules appeared. However, when the inhibitor for Ca2+-proteinase was included in Triton lysis buffer, the microfilaments remained intact. These results suggested that an increase in Ca2+ concentration to more than 5 X 10(-7) M not only makes myosin associate with cytoskeletons but also regulates the organization of filamentous structures.
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PMID:Effect of calcium on protein composition of human platelet cytoskeletons. 293 Nov 20

To clarify the characteristics of myosin isozymes in the atrium, we fractionated two isoforms of myosin heavy chain (HC), atrial HC alpha (A-HC alpha) and HC beta (A-HC beta), from the canine heart by affinity chromatography, using monoclonal antibodies specific for HC alpha (CMA19) and HC beta (HMC50), respectively, and then compared their peptide composition and enzymatic properties with those of ventricular HC alpha (V-HC alpha) and HC beta (V-HC beta). The reactivity of these isozymes with three monoclonal antibodies revealed that there are at least three different epitopes between A-HC alpha and A-HC beta. Differences in the primary structure of A-HC alpha and A-HC beta were confirmed by one- and two-dimensional gel electrophoretic analyses of these peptides, produced by digestion with alpha-chymotrypsin and cyanogen bromide (CNBr). A-HC alpha and V-HC alpha were indistinguishable proteins, and A-HC beta was also very similar to V-HC beta. Furthermore, there were differences between A-HC alpha and A-HC beta in their Ca2+-activated ATPase activities. The ATPase activity of A-HC beta was lower than that of A-HC alpha and was similar to that of V-HC beta. We concluded that there are two different isozymes of myosin heavy chain in the atrium (A-HC alpha and A-HC beta), as well as in the ventricle (V-HC alpha and V-HC beta), and that A-HC beta is very similar to V-HC beta, the predominant form of ventricular myosin, in its molecular structure and enzymatic activity.
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PMID:Isolation and characterization of two isozymes of myosin heavy chain from canine atrium. 293 78

Our results show that calcium activation of myofilament preparations of dog heart in the perinatal period is unaffected by a reduction in pH from 7.0 to 6.5, which, in adult heart myofilaments, induces a 0.4 pCa unit (-log molar free calcium concentration) rightward shift in the relation between pCa and myofibrillar adenosine triphosphatase activity. Acidic pH also had no effect on calcium binding to myofibrillar troponin C of perinatal hearts. The stoichiometry of troponin C bound calcium at full myofilament activation (about 3 mol calcium/mol troponin C) was the same for adult and perinatal heart myofibrils, as was their myofibrillar troponin C content. Moreover, there were no differences in isoelectric pH of troponin C from adult and perinatal hearts. We tested whether variants of myofilament proteins other than troponin C could account for the differential effects of acidic pH. In adult and perinatal dog heart preparations, myosin heavy chain isoenzymes appeared the same as measured, using native pyrophosphate gel electrophoresis. No evidence for thick filament-related calcium regulation in the perinatal heart myofilaments was obtained, when tested in studies in which native thin filaments were displaced with a 10-fold molar excess of pure actin. In preparations in which native thick filaments were displaced with a 10-fold molar excess of pure skeletal muscle myosin, the effects of acidic pH on calcium activation were the same as in native adult and perinatal preparations. Our major conclusion from these results in that the perinatal heart myofilaments are likely to possess variations in thin filament activity and structure.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Differential effects of pH on calcium activation of myofilaments of adult and perinatal dog hearts. Evidence for developmental differences in thin filament regulation. 294 29

Monoclonal antibodies that react with defined regions of the heavy and light chains of chicken skeletal muscle myosin have been used to provide a correlation between the primary and the tertiary structures of the head. Electron microscopy of rotary shadowed antibody-myosin complexes shows that the sites for three epitopes in the 25,000 Mr tryptic fragment (25k) of subfragment-1, including one within 4000 Mr of the amino terminus of the myosin heavy chain, are clustered 145(+/- 20) A from the head-rod junction. An epitope in the 50,000 Mr fragment maps even further out on the head. These antibodies bind to the head in several orientations, suggesting that each of the heads can rotate can rotate 180 degrees about the head-rod junction. The epitopes are accessible on subfragment-1 bound to actin when they were probed with Fab fragments; therefore, none of these heavy chain sites is is on the contact surface between the head and actin. Two of the anti-25k antibodies affect the K+-EDTA-and Ca2+-ATPase activities of myosin in a manner that mimics the effect on activity of the modification of the reactive thiol, SH-1. These two antibodies also inhibit the actin-activated ATPase non-competitively with respect to actin. None of the other eight antibodies tested had any marked effect on activity. A monoclonal antibody that reacts with an epitope in the amino-terminal third of myosin light chain 2 maps close to the head-rod junction. A polyclonal antibody specific for the amino terminus of light chain 3 binds further up in the "neck region" of the head, indicating that these portions of the two classes of light chains are located at different sites.
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PMID:Probing myosin head structure with monoclonal antibodies. 294

A high molecular weight polypeptide, identified as an ATPase subunit by direct ultraviolet photoaffinity labeling, has been shown to be a component of nuclear envelope-enriched fractions prepared from a variety of higher eukaryotes (Berrios, M., G. Blobel, and P. A. Fisher, 1983, J. Biol. Chem., 258:4548-4555). In rat liver as well as Drosophila melanogaster embryos, this polypeptide appears to be a form of myosin heavy chain. This conclusion is based on both immunochemical and immunocytochemical data, as well as on the results of CNBr and chymotryptic peptide map analyses. In Drosophila, the identification of this myosin heavy chain-like polypeptide as a nuclear envelope component has been corroborated in situ by indirect immunofluorescence analyses using permeabilized whole cells, mechanically extruded nuclei, and cryosections obtained from a number of larval tissues. Localization appears to be restricted to the nuclear periphery in a manner similar to that observed for the nuclear lamins and the pore complex glycoprotein. Antibodies directed against the Drosophila nuclear envelope ATPase have also been shown to decorate mammalian and higher plant cell nuclei in situ. Implications for intracellular nuclear mobility and for nucleocytoplasmic exchange of macromolecules in vivo are discussed.
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PMID:A myosin heavy-chain-like polypeptide is associated with the nuclear envelope in higher eukaryotic cells. 294 45

Distinct myosin isoforms were identified from the ventricles and atria of foetal, normal and hypertrophied human hearts. Ventricle and atrium myosins cannot be differentiated by their sedimentation behaviour in the analytical ultracentrifuge, they vary, however, with regard to the Ca2+-dependent ATPase and also the activation parameters in measurements of the enzyme activity in dependence on temperature. In agreement with other authors we observed a foetal light chain in the ventricular tissue of the latter half of gestation, when myosin was characterized by SDS-polyacrylamide gel electrophoresis and isoelectric focusing. Using pyrophosphate gel electrophoresis an additional foetal isomyosin was observed besides the typical ventricular myosin HV-3, which migrates faster. Two distinct myosin isoforms designated as HA-3 and HA-1 occur in the atrium of the normal human heart. It was found that besides their own isoenzymes normal atria also contain ventricular isomyosin, whose relative proportion is markedly increased in the hypertrophic atrium. In contrast, we usually observed only one isoenzyme in the normal ventricle. Moreover, in case of myocardial infarction a dramatic transformation of myosin heavy chain composition with a shift to an atrial myosin type took place in the ventricle.
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PMID:Myosin isoenzymes in normal and hypertrophied human hearts. 294 91

The thiol of the gizzard myosin heavy chain, which reacts most rapidly with N-ethylmaleimide (MalNEt), has been located in the subfragment 2 region of myosin rod by fragmentation of [14C]-MalNEt-labeled myosin with papain and chymotrypsin. MalNEt reacts more slowly with thiols present in the 70- and 25-kilodalton (kDa) papain fragments of subfragment 1. The reaction of MalNEt with thiols present in these regions is increased on addition of ATP by factors of 2 and 10, respectively, when myosin is modified in 0.45 M NaCl where it is present in the extended, 6S conformation. The rate of increase of Mg2+-activated adenosinetriphosphatase (ATPase) activity, which reflects the loss of ability of myosin to assume the folded, 10S conformation, and the rate of loss of K+-EDTA-activated activity produced by MalNEt are both accelerated 5- to 10-fold on addition of ATP. The rates at which ATPase activities change agree closely to the reaction rates of MalNEt with the 25-kDa region of subfragment 1; therefore, the changes in these activities can be attributed to modification of a thiol of the 25-kDa segment. An increase in actin-activated ATPase activity produced by reaction of myosin with MalNEt in 0.45 M NaCl is accelerated by ATP by a factor of at least 4. Reaction with [14C]MalNEt in the presence of MgATP and 0.2 M NaCl, where myosin is in the 10S form, inhibits the incorporation of radioactive MalNEt into the 25-kDa papain fragment of subfragment 1. It also prevents the increase in actin-activated ATPase activity and preserves the ability of myosin to assume the 10S form.
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PMID:Location of the sites of reaction of N-ethylmaleimide in papain and chymotryptic fragments of the gizzard myosin heavy chain. 294 24


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