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)

Alterations of cardiac contractility caused by thiamine deficiency were studied on three groups of 2 month old male Wistar rats: B1, fed a thiamine deficient diet, PF pair fed, which received an amount of thiamine free diet determined on the daily consumption of B1 animals, supplemented with appropriate thiamine supply, C ad libitum fed controls. The animals were studied after 35 days of dietary treatment. Force-velocity curves were determined in right ventricle papillary muscles. Shortening velocity was significantly lower in B1 and PF than in C muscles and in B1 than in PF muscles. The ability to develop tension was not altered. Myosin ATPase activity was assayed in preparations of myofibrils and in preparations of purified myosin. Both Ca-Mg activated myofibrillar ATPase activity and Ca-activated myosin ATPase activity were significantly reduced in B1 and PF compared to C myocardium. Furthermore Ca-activated ATPase activity was lower in B1 than in PF myocardium. Myosin isoenzyme distribution was determined by pyrophosphate gel electrophoresis of purified myosin preparations. When compared to C animals both B1 and PF animals showed a myosin electrophoretic pattern shifted towards the slow isoform V3; such a shift was more pronounced in B1 animals. Information concerning excitation-contraction coupling was obtained by determining the steady state and transient force-interval relation and by recording transmembrane action potential. B1 and PF myocardium exhibited, when compared to C, a less sensitivity to a reduction of the interval of stimulation, a faster mechanical restitution, a prolonged action potential duration. Such alterations were generally more pronounced in B1 than in PF myocardium. The results support the view that in the rat cardiac contractility is deeply affected by thiamine deficiency. The alterations of cardiac contractility seem to be caused by adaptive mechanisms rather than by cardiac failure and seem to be attributable for a big part to the reduction of food supply.
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PMID:Altered contractile properties of rat cardiac muscle during experimental thiamine deficiency and food deprivation. 215 36

Thyroid hormone-induced changes in cardiac function have been recognized for over 150 years; however, the biochemical basis of triiodothyronine (T3) action in the heart has been intensely investigated only during the last two decades. T3-induced changes in cardiac function can result from direct or indirect T3 effects. Direct T3 effects result from T3 action in the heart itself and are mediated by nuclear or extranuclear mechanisms. Extranuclear T3 effects, which occur independent of nuclear T3 receptor binding and increases in protein synthesis, influence primarily the transport of amino acids, sugars, and calcium across the cell membrane. Nuclear T3 effects are mediated by the binding of T3 to specific nuclear receptor proteins, which results in increased transcription of T3-responsive cardiac genes. The T3 receptor is a member of the ligand-activated transcription factor family and is encoded by cellular erythroblastosis A (c-erb A) genes. The c-erb A protein is the cellular homologue of the viral erythroblastosis A (v-erb A) protein, which causes red cell leukemia in chickens. Currently, three T3-binding isoforms of the c-erb protein and two non-T3-binding nuclear proteins that exert positive and negative effects on T3-responsive cardiac genes have been identified. T3 increases the heart transcription of the myosin heavy chain (MHC) alpha gene and decreases the transcription of the MHC beta gene, leading to an increase of myosin V1 and a decrease in myosin V3 isoenzymes. Myosin V1, which is composed of two MHC alpha, has a higher myosin ATPase activity than myosin V3, which contains two MHC beta. The globular head of myosin V1, with its higher ATPase activity, leads to a more rapid movement of the globular head of myosin along the thin filament, resulting in an increased velocity of contraction. T3 also leads to an increase in the speed of diastolic relaxation, which is caused by the more efficient pumping of the calcium ATPase of the sarcoplasmic reticulum (SR). This T3 effect results from T3-induced increases in the level of the mRNA coding for the SR calcium ATPase protein, leading to an increased number of calcium ATPase pump units in the SR. Overall, thyroid hormone leads to an increase in ATP consumption in the heart. In addition, less chemical energy of ATP is used for contractile purposes and more of it goes toward heat production, which causes a decreased efficiency of the contractile process in the hyperthyroid heart.
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PMID:Biochemical basis of thyroid hormone action in the heart. 218 6

Monoclonal antibodies to myosins have been used to describe and define the appearance and maturation of 3 different classes of myotube in developing human quadriceps muscle. Five monoclonal antibodies were used: (i) MAb A against human slow myosin heavy chain; (ii) MAb B against a myosin heavy chain present in most adult Type 2 fibres; (iii) MAb C against myosin heavy chain present in all mature and immature Type 2 fibres; (iv) MAb D, with similar reactivity to MAb C; (v) MAb E against human embryonic myosin. The combined use of two of these antibodies (A and B) enables the confident early identification of each of 3 classes (primary, secondary, tertiary) of myotubes, which appear sequentially during myogenesis. Our results show that induction of slow myosin heavy chain synthesis is a biphasic phenomenon in developing human skeletal muscle. Slow myosin heavy chain was present in all the earliest (9 weeks gestation) primary myotubes, but was not detected in secondary or tertiary myotubes until about 29 weeks gestation. Each stage of fetal muscle development has a characteristic immunocytochemical pattern which reveals cellular heterogeneity not evident on myosin ATPase histochemistry. Myosin immunocytochemistry may usefully be applied to assess the gestational age of fetuses. A new interpretation of human skeletal muscle development is proposed, based on the separate programming of 3 different kinds of myotube. This may be important in the analysis of diseased muscle in which developmental abnormalities or regeneration are present.
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PMID:Primary, secondary and tertiary myotubes in developing skeletal muscle: a new approach to the analysis of human myogenesis. 244 24

Myosin ATPase activity is usually considered to reflect the contractile capacity of a given muscle since it correlates with the maximum initial speed of shortening of the unloaded muscle (Vmax). There are several exceptions to this scheme, and it was the goal of this study to determine if the Mg2+-ATPase activity of the covalently bound actomyosin S1 is a more physiological index of contractility. On polyacrylamide gels, the complex obtained after condensation of fast skeletal myosin S1 to skeletal actin is identical to that obtained with myosin S1 from the ventricles of different species, including rat, guinea pig, and human, cross-linked to cardiac or skeletal actin. In every condition, the ATPase activity of the complex is 700-fold higher than that of myosin S1. It correlates linearly with the Vmax both in phylogeny and in conditions in which an isomyosin shift has been reported, such as hypothyroidism and chronic cardiac overload. Such a relation indicates that, in species that already have a low Vmax, a small change in myosin ATPase may induce dramatic consequences in the shortening velocity. Cardiac hypertrophy in humans, where the drop in Vmax is not associated with a myosin change, does not fit into this scheme. The enzymatic activity of the complex is also unmodified in this condition, which shows that, in humans, the myosin ATPase is not a determinant of Vmax and suggests that other mechanisms may be involved. Measurement of this type of ATPase activity provides a new tool to explore contractility biochemically, which is more reproducible and, from a technical point of view, easier to perform than a kinetic assay. It also correlates better with mechanical data obtained with skinned fibers than with those measured on fresh papillary muscles.
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PMID:ATPase activity of the cross-linked complex between cardiac myosin subfragment 1 and actin in several models of chronic overloading. A new approach to the biochemistry of contractility. 252 89

Myosin was isolated from the ventricular myocardium of adult rats and the effect of time, 2-mercaptoethanol and inhibitors of proteases was investigated on its properties. It was found that the storage of cardiac muscle up to 4 hours does not influence the myosin ATPase, the electrophoretic pattern of light chains of myosin or the pattern of peptides produced by digestion of myosin with chymotrypsin. Neither does the presence of pepstatin and phenylmethyl sulfonylfluoride during myosin preparation influence the activity of myosin ATPase. It was found that the presence of 2-mercaptoethanol during myosin preparation enhances myosin ATPase of the product. This myosin was more stable when kept at 4 degrees C for four days.
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PMID:The effect of time, 2-mercaptoethanol and inhibitors of proteases on isolation of cardiac myosin and its properties. 252 75

The effect of an affinity modifier of myosin ATPase representing a mixed anhydride of AMP and mesitylene carboxylic acid (AMP-MA) on myosin with protected active centers was studied. The protection of active centers was performed by the method of Wells et al. Which consists in the stabilization of the myosin-MgADP complex in the enzyme active center by way of cross-linking of the active center with a Co-phenanthroline complex simultaneously interacting with two SH-groups of the protein. Myosin with protected active center completely loses its ability to hydrolyze ATP; however, it can be reactivated by way of SH-group reduction with a subsequent MgADP release from the active centers. Treatment of myosin with protected active centers with AMP-MA does not result in the reduction of the enzyme activity after removal of the Co-phenanthroline complex. This suggests that the irreversible inhibition of myosin ATPase by AMP-MA occurs due to the protein modification outside the active center(s), which provides support for our earlier made conclusion concerning the existence of an additional (with respect to active centers) substrate-binding site in the myosin molecule.
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PMID:[Affinity modification of myosin with protected active centers: confirmation of the existence of an allosteric substrate-binding segment]. 253 15

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

Cultured neonatal rat heart cells are a useful model for studying the regulation of myocyte growth. The myosin content of heart cells increases between days 1 and 4 in culture. To determine if contraction per se can regulate myocyte growth, myosin content and protein synthesis were compared in spontaneously contracting and noncontracting cultured heart cells. Myosin content, assayed as the total myosin ATPase activity per culture dish, was significantly increased in contracting cells after 3, 4, and 5 days in culture. Protein synthesis was measured by incorporation of [14C]lysine into total cell protein and into sodium dodecyl sulfate-polyacrylamide gel electrophoresis resolved myosin. Contraction stimulated both total cell protein content and protein synthesis by day 3 in culture. Compared with heart cells arrested with 50 mM KCl, myosin synthesis was significantly increased by 96, 112, and 46% at days 2, 3, and 4, respectively. Similar results were observed when myosin content and protein synthesis in contracting myocytes were compared with cells arrested with either 25 mM KCl or 10(-5) M verapamil. The present studies suggest that contraction increases the myosin content in cultured heart cells and that this increase is mediated via a stimulation of myosin synthesis in association with cell growth.
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PMID:Contraction regulates myosin synthesis and myosin content of cultured heart cells. 293 98

Myosin was isolated from amoebae of Physarum polycephalum and compared with myosin from plasmodia, another motile stage in the Physarum life cycle. Amoebal myosin contained heavy chains (Mr approximately 220,000), phosphorylatable light chains (Mr 18,000), and Ca2+-binding light chains (Mr 14,000) and possessed a two-headed long-tailed shape in electron micrographs after rotary shadow casting. In the presence of high salt concentrations, myosin ATPase activity increased in the following order: Mg-ATPase activity less than K-EDTA-ATPase activity less than Ca-ATPase activity. In the presence of low salt concentrations, Mg-ATPase activity was activated approximately 9-fold by skeletal muscle actin. This actin-activated ATPase activity was inhibited by micromolar levels of Ca2+. Amoebal myosin was indistinguishable from plasmodial myosin in ATPase activities and molecular shape. However, the heavy chain and phosphorylatable light chains of amoebal myosin could be distinguished from those of plasmodial myosin in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, peptide mapping, and immunological studies, suggesting that these are different gene products. Ca2+-binding light chains of amoebal and plasmodial myosins were found to be identical using similar criteria, supporting our hypothesis that the Ca2+-binding light chain plays a key role in the inhibition of actin-activated ATPase activity in Physarum myosins by micromolar levels of Ca2+.
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PMID:Isolation and characterization of myosin from amoebae of Physarum polycephalum. 294 Feb 48


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