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)

The pattern of incorporation of [14C]N-ethylmaleimide (MalNEt) into gizzard myosin indicates the presence of two classes of thiols: rapidly and slowly modified. The first class contains two thiol residues, SH-A and SH-B, located in the myosin rod and the 17-kDa light chain, respectively, while the second contains at least two thiols located in the myosin heavy chain. Changes in ATPase activities upon modification occur rapidly or slowly, paralleling reaction of either the first or second class of thiols. Rapid changes include increases in the Ca2+- and Mg2+-activated activities of myosin alone, measured at ionic strengths below 0.3 M, and an increase and a decrease in the actin-activated activity of dephosphorylated and phosphorylated myosin, respectively. Modification of SH-A and SH-B with MalNEt is accompanied by stabilization of myosin filaments, seen as an increase in light-scattering intensity, and by destabilization of the folded, 10 S conformation of the myosin monomer. In the presence of 0.175 M NaCl and 1 mM MgATP, unmodified and MalNEt-modified myosin sediment in the ultracentrifuge as single components at 10.0 S and 6.0 S, respectively. The MalNEt-induced increase in the Ca2+- or Mg2+-activated ATPase activity, measured in the absence of actin, can be attributed either to stabilization of filaments or to destabilization of the 10 S conformation, depending on the ionic strength of the assay. Modification of the second class of thiols is accompanied by a decrease in K+-EDTA-activated activity and an increase in Ca2+-activated activity measured above 0.3 M NaCl, where myosin neither forms filaments nor assumes the 10 S conformation. These slow changes are characteristic of blocking the SH-1 thiols of skeletal-muscle myosin, but in gizzard myosin are attributable to modification of a less reactive thiol, SH-C.
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PMID:Modification of thiols of gizzard myosin alters ATPase activity, stability of myosin filaments, and the 6-10 S conformational transition. 315 16

Fast and slow muscles from the claws and abdomen of the American lobster Homarus americanus were examined for adenosine triphosphatase (ATPase) activity and for differences in myofibrillar proteins. Both myosin and actomyosin ATPase were correlated with fiber composition and contractile speed. Four distinct patterns of myofibrillar proteins observed in sodium dodecyl sulfate-polyacrylamide gels were distinguished by different assemblages of regulatory and contractile protein variants. A total of three species of troponin-T, five species of troponin-I, and three species of troponin-C were observed. Lobster myosins contained two groups of light chains (LC), termed "alpha" and "beta." There were three alpha-LC variants and two beta-LC variants. There were no apparent differences in myosin heavy chain, actin, and tropomyosin. Only paramyosin showed a pattern completely consistent with muscle fiber type: slow fibers contained a species (105 kD) slightly smaller than the principle variant (110 kD) in fast fibers. It is proposed that the type of paramyosin present could provide a biochemical marker to identify the fiber composition of muscles that have not been fully characterized. The diversity of troponin and myosin LC variants suggests that subtle differences in physiological performance exist within the broader categories of fast- and slow-twitch muscles.
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PMID:Heterogeneity of myofibrillar proteins in lobster fast and slow muscles: variants of troponin, paramyosin, and myosin light chains comprise four distinct protein assemblages. 315 73

The proteolysis of gizzard myosin by Staphylococcus aureus protease produces both heavy meromyosin and subfragment 1 in which the 20 000-dalton light chains are intact, and conditions are suggested for the preparation of each. Cleavage of the myosin heavy chain to produce subfragment 1 is dependent on the myosin conformation. Proteolysis of myosin in the 10S conformation yields predominantly heavy meromyosin, and myosin in the 6S conformation yields mostly subfragment 1 and some heavy meromyosin. Two sites are influenced by myosin conformation, and these are located at approximately 68 000 and 94 000 daltons from the N-terminus of the myosin heavy chain. The latter site is thought to be located at the subfragment 1-subfragment 2 junction, and cleavage at this site results in the production of subfragment 1. The time courses of phosphorylation of both heavy meromyosin and subfragment 1 can be fit by a single exponential. The actin-activated Mg2+-ATPase activity of heavy meromyosin is markedly activated by phosphorylation of the 20 000-dalton light chains. From the actin dependence of Mg2+-ATPase activity the following values are obtained: for phosphorylated heavy meromyosin, Vmax approximately 5.6 s-1 and Ka (the apparent dissociation constant for actin) approximately 2 mg/mL; for dephosphorylated heavy meromyosin, Vmax approximately 0.2 s-1 and Ka approximately 7 mg/mL. The actin-activated ATPase activity of subfragment 1 is not influenced by phosphorylation, and Vmax and Ka for both the phosphorylated and dephosphorylated forms are 0.4 s-1 and 5 mg/mL, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Proteolysis of smooth muscle myosin by Staphylococcus aureus protease: preparation of heavy meromyosin and subfragment 1 with intact 20 000-dalton light chains. 315 49

We have previously demonstrated, based on comparison of homologous amino acid sequences and of two-dimensional CNBr peptide gel patterns, that the myosin heavy chain in pectoralis muscles of Storrs, Connecticut dystrophic chickens is different from that of their normal controls (Huszar, G., Vigue, L., De-Lucia, J. Elzinga, M., and Haines, J. (1985) J. Biol. Chem. 260, 7429-7434). Others have shown, however, that genomic banks and mRNA complements of the control and dystrophic birds are not different. In the present studies, we have examined the hypothesis that the "dystrophic" myosin heavy chain is not a novel gene product, but is a developmental isozyme which is expressed in pectoralis muscles of adult chickens due to the dystrophic process. Two-dimensional maps of myosin heavy chain CNBr peptides were prepared from breast muscles of 17-day in ovo (embryonic), 25-day posthatch (neonatal), and adult birds of the Storrs dystrophic and of two control strains. Also, myosin and actomyosin ATPase enzymatic activities of the various preparations were determined in the pH range of 5.5 to 9.0. Analysis of the peptide maps demonstrates that the embyronic, neonatal, and control adult myosin heavy chain isozymes are distinctly different gene products with only minute variations between the respective developmental isozymes in dystrophic and control muscles. However, the pectoralis myosin heavy chain of adult dystrophic birds, which is a homogeneous isozyme population by amino acid sequences and gel patterns, corresponds to that of the neonatal-type myosin heavy chain. The ATPase properties of the embryonic, neonatal, or adult pectoralis myosins and actomyosins were not different, whether the level of specific activity or the pattern of pH activation is considered. Since the mobility of neonatal chicks (primarily neonatal-type isozymes) is not restricted, the differences in myosin heavy chain structures are part of the syndrome, but not the cause of avian muscular dystrophy.
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PMID:Myosin heavy chain in avian muscular dystrophy corresponds to the neonatal isozyme. 316 Jul 8

Previous experiments demonstrated that two thiols of skeletal myosin subfragment 1 (SF1) could be oxidized to a disulfide bond by treatment with a 2-fold excess of 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) in the presence of MgADP [Wells, J. A., & Yount, R. G. (1980) Biochemistry 19, 1711-1717]. The resulting characteristic changes in the ATPase activities of SF1 and the fact that MgADP was stably trapped at the active site [Wells, J. A., & Yount, R. G. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 4966-4970] suggested that the two thiols cross-linked were SH1 (Cys-707) and SH2 (Cys-697) from the myosin heavy chain. To verify this suggestion, SF1, after DTNB treatment as above, was treated with an excess of N-ethylmaleimide to block all accessible thiols. The single protein disulfide produced by DTNB oxidation was reduced with dithioerythritol and the modified SF1 internally cross-linked with equimolar [14C]p-phenylenedimaleimide (pPDM) in the presence of MgADP. After extensive trypsinization, the major 14C-labeled peptide was isolated, characterized, and shown to be Cys-Asn-Gly-Val-Leu-Gly-Ile-Arg-Ile-Cys-Arg, in which the two cysteines were cross-linked by pPDM. This peptide is known to contain SH2 and SH1 in this order and to come from residues 697-708 in the rabbit skeletal myosin heavy chain [Elzinga, M., & Collins, J. (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 4281-4284; M. Elzinga, personal communication].(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Flexibility of the myosin heavy chain: direct evidence that the region containing SH1 and SH2 can move 10 A under the influence of nucleotide binding. 323 15

Chicken gizzard myosin was modified with N-iodoacetyl-N'-(5-sulfo-1-naphthyl)-ethylenediamine (IAEDANS) in the presence of ATP and in 0.15 M KCl, where the myosin assumed 10S conformation. From the tryptic digest of the modified myosin, a fluorescent fragment (24 kilodaltons) was isolated by gel filtration on a Sephadex G-100 column followed by chromatography on a CM 52 column. The amino acid sequence of the fragment was analyzed by conventional methods, and was: (S,Z)K-P-L-S-D-D-E-K-F-L-F-V-D-K-N-F-V-N-N-P-L-A-Q-A-D-W-S-A-K-K- L-V-W-V-P-S-E-K-H-G-F-E-A-A-S-I-K-E-E-K-G-D-E-V-T-V-E-L-Q-E-N-G-K-K- V-T-L-S-K-D-D-I-Q-K-M-N-P-P-K-F-S-K-V-E-D-M-A-E-L-T-C-L-N-E-A-S-V-L- H-N-L-R-E-R-Y-F-S-G-L-I-Y-T-Y-S-G-L-F-C-V-V-I-N-P-Y-K-Q-L-P-I-Y-S-E-K-I- I-D-M-Y-K-G-K-K-R-H-E-M-P-P-H-I-Y-A-I-A-D-T-A-Y-R-S-M-L-Q-D-R-E-D-Q- S-I-L-C-T-G-E-S-G-A-G-K-T-E-N-T-K-K-V-I-Q-Y-L-A-V-V-A-S-S-H-K-G-K. The amino-terminus was blocked, and the fragment was assigned as an amino-terminal part of the heavy chain of gizzard myosin. Position 127 was occupied by epsilon-N-trimethyllysine. Trp-130 of rabbit skeletal myosin heavy chain, which was reported to cross-link to an azide derivative of ATP by Okamoto and Yount (Proc. Natl. Acad. Sci. U.S. 82, 1575-1579 (1985], was replaced by glutamine in gizzard myosin. Cys-93 of the fragment is the amino acid residue whose reaction with IAEDANS alters the ATPase activity of gizzard myosin (Onishi, H. (1985) J. Biochem. 98, 81-86).
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PMID:Amino acid sequence of the amino-terminal 24 kDa fragment of the heavy chain of chicken gizzard myosin. 331 84

Tension is an important regulator of skeletal muscle hypertrophy in vivo. When increased constant tension is applied to embryonic skeletal muscle fibers differentiated in a tissue culture environment, many of the same biochemical processes associated with muscle hypertrophy in vivo are also stimulated in vitro, e.g., sodium-dependent amino acid transport, Na+,K+-ATPase (sodium pump) activity, protein synthesis, total protein, and myosin heavy chain accumulation. The molecular mechanisms by which tension induces these growth-related changes are unknown, but several models have been tested using whole animal, organ-cultured muscle, and tissue culture model systems. In tissue culture, activation of the plasma membrane sodium pump is closely coupled to, and essential for, stretch and serum-induced skeletal muscle growth. Long-term membrane hyperpolarization is not associated with this sodium pump activation, and muscle growth in vitro is unrelated to the myotube's resting membrane potential, since growth can occur under de-polarizating conditions. Medium growth factors are essential for stretch-induced muscle growth in tissue culture. In medium without growth factor supplements, stretch is able to reduce the rate of atrophy of the cultured muscle cells which are in negative nitrogen balance, but the muscle cells are unable to grow in response to stretch without the presence of some as yet undefined growth factor or factors present in serum. As newer tissue culture environments are designed for growing embryonic skeletal muscle under more in vivo-like conditions, a more complete analysis of the mechanisms by which a physical stimulus (tension) is translated into the biochemical alterations leading to muscle growth will be possible.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Motion into mass: how does tension stimulate muscle growth? 331 13

The role of contractile proteins in secretory granule exocytosis was evaluated by determining whether myosin light chain phosphorylation was altered during stimulation of secretion in mouse pancreatic acini. Acinar myosin was purified by extraction into isosmotic sucrose solution containing 40 mM pyrophosphate followed by ammonium sulfate precipitation and Sepharose 4B-CL chromatography. Myosin was eluted as a single peak of K+-EDTA ATPase activity and was purified over 2,000-fold to a final ATPase specific activity of 0.96 mumol.min-1.mg protein-1. Three major myosin subunits of apparent Mr of 200,000, 20,000, and 17,000 were present in the purified myosin preparation. A fourth protein of Mr 21,000 was also present. Purification of myosin from 32P-labeled acini revealed the Mr 200,000, 21,000, and 20,000 proteins to be heavily labeled. The effect of cholecystokinin octapeptide (CCK-8) on myosin phosphorylation was studied after isolation of myosin from 32P-labeled acinar lysates by immunoprecipitation. Treatment of acini for 1-10 min with a concentration of CCK-8 that gives a maximal secretory response caused a 25-40% increase in light chain labeling. Treatment with a supramaximal CCK-8 concentration produced a 50-80% increase in light chain labeling. Phosphorylation of myosin heavy chain was not significantly affected by secretagogue treatment. These results indicate that stimulation of pancreatic acinar secretion is accompanied by an increase in myosin light chain phosphorylation.
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PMID:Evaluation of myosin light chain phosphorylation in isolated pancreatic acini. 333 33

Two myosin heavy chains (MHCs), alpha and beta, which exhibit different levels of ATPase activity related to the different velocities of muscle shortening, are differentially expressed in rat cardiac ventricles, depending on the developmental stage and the thyroid status of the animals. In contrast, no changes have been reported concerning the expression of atrial MHCs in the same physiological and pathological conditions. We have now performed studies with sensitive techniques to test the hypothesis that the expression of alpha- and beta-MHCs can also be modulated in the rat atria, although at a low level. Atrial and ventricular isomyosin patterns of various groups of rats were examined by two-dimensional peptide mapping, immunofluorescence with specific anti-alpha- and anti-beta-MHC immunoglobulins, and electrophoresis under nondenaturing conditions. Normal ontogenic development of the atria is characterized by the disappearance of a small amount of beta-MHC, present at 19 days in utero. At 3 wk of age, atria and ventricles both contain only alpha-MHC. Severe hypothyroidism, produced either by methylthiouracil (MTU) treatment of pregnant females and of their litters or by hypophysectomy of adult animals, did not significantly deinduce atrial alpha-MHC but was characterized by a significant although slight accumulation of beta-MHC (less than 5% of total myosin). This latter effect was abolished by L-thyroxine restoration. It is concluded that alpha- and beta-MHC are developmentally and hormonally regulated both in atria and ventricles, although the extent of regulation is very different for the two tissues.
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PMID:Differential effect of thyroxine on atrial and ventricular isomyosins in rats. 351 24

The complete sequence of an embryonic chicken myosin heavy chain has been determined. Introns and exons were identified by comparison with the corresponding cDNA. The cDNA contains 5,962 bases, of which 85 bases constitute the poly(A) tail. The cDNA represents the entire mRNA transcript, except for 90 bases at the 5'-coding terminus and 101 bases of the 5'-untranslated region. The gene's coding region is split by 37 introns; two additional introns split the 101 base pairs which make up the 5'-untranslated region. The complete gene is approximately 23,000 base pairs and encodes a protein whose molecular weight is 222,559 and consists of 1,940 amino acids. Analysis of the protein and comparison with other myosin sequences reveal that certain regions have been conserved; those amino acids which have been postulated to participate in the ATPase and actin-binding activities of the molecule are highly homologous. These comparisons have allowed the identification of isolated regions within the myosin heavy chain that appear to be essential for the molecule's function.
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PMID:The sequence of an embryonic myosin heavy chain gene and isolation of its corresponding cDNA. 357 Dec 66


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