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)

Single muscle fibres were isolated by microdissection from freeze-dried samples of rabbit psoas and soleus muscles. The individual fibres were typed according to qualitative histochemical reactions for succinate dehydrogenase or NADH-tetrazolium reductase and for alkaline Ca2+-activated myofibrilla myosin ATPase after acid or alkaline preincubation. Methods are described for electrophoretic analysis by means of polyacrylamide disc electrophoresis in the presence of SDS of total myofibrilla proteins in single fibres after pre-extraction of soluble proteins. Fast-twitch white fibres revealed a myosin light chain pattern characteristic of "fast- type" myosin with three light chains of apparent molecular weights of 22,300 (LC1) 18,400 (LC2) and 16,000 (LC3). Fast-twitch red fibres were indistinguishable in this respect from fast-twist white fibres and showed an identical pattern of myosin light chains. Slow-twitch fibres could be characterized by a myosin light chain pattern typical of myosin of slow-twitch muscles with peptides of the apparent molecular weights of 23,500 (LC1Sa), 23,000 (LC1Sb) and 18,500 (LS2S). Slow-twitch fibres isolated from soleus as well as from psoas muscle were indistinguishable with regard to their myosin light chain patterns, thus suggesting that fibres of the same histochemical type correspond in their myosin light chain patterns irrespective of their origin from different muscles.
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PMID:Myosin light chain patterns of individual fast and slow-twitch fibres of rabbit muscles. 14 18

Myosin was purified from rabbit alveolar macrophages in a form that could not be activated by actin. This myosin could be phosphorylated by an endogenous myosin light chain kinase, up to 2 mol of phosphate being incorporated/mol of myosin. The site phosphorylated was located on the 20,000-dalton myosin light chain. Phosphorylation of macrophage myosin was found to be necessary for actin activation of myosin ATPase activity. Moreover, the actin-activated ATPase activity was found to vary directly with the extent of myosin phosphorylation, maximal phosphorylation (2 mol of Pi/mol of myosin) resulting in an actin-activated MgATPase activity of approximately 200 nmol of Pi/mg of myosin/min at 37 degrees C. These results establish that phosphyoyration of the 20,000-dalton light chain of myosin is sufficient to regulate the actin-activated ATPase activity of macrophage myosin.
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PMID:Macrophage myosin. Regulation of actin-activated ATPase, activity by phosphorylation of the 20,000-dalton light chain. 15 17

A quantitative histochemical technique was developed for determining the kinetics of the calcium-activated myosin ATPase (Ca(2+)-myosin ATPase) reaction in rat skeletal muscle fibres. Using this technique, the maximum velocity (Vmax) and the apparent Michaelis-Menten rate constant for ATP (K(app)) of the Ca(2+)-myosin ATPase reaction were measured in type-identified fibres of the rat medial gastrocnemius (MG) muscle. The Vmax and the K(app) of the Ca(2+)-myosin ATPase reaction were lowest in type I fibres and highest (i.e., approx. two times greater) in type IIb fibres. The K(app) in type IIa fibres was similar to that in type I. However, the Vmax was 1.5 times greater in type IIa fibres, compared to type I fibres. Evidence is presented to suggest that the type IIb fibre population in the MG does not represent a single myosin isozyme. In addition, the broad range of Vmax and K(app) values indicates that there is marked heterogeneity in the myosin heavy chain and myosin light chain composition of myosin isozymes among individual fibres.
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PMID:Quantitative determination of calcium-activated myosin adenosine triphosphatase activity in rat skeletal muscle fibres. 138 25

Recently, one of the authors (K.I.) and other investigators reported that myosin light chain (MLC) of smooth muscle (gizzard, arterial and tracheal) was diphosphorylated by myosin light chain kinase (MLCK) and that diphosphorylated myosin showed a marked increase in the actin-activated myosin ATPase activity in vitro and ex vivo. In this study, we prepared myosin, actin, tropomyosin (human platelet), MLCK (chicken gizzard) and calmodulin (bovine brain) and demonstrated diphosphorylation of MLC of platelet by MLCK in vitro. Our results are as follows. (1) Platelet MLC was diphosphorylated by a relatively high concentration (greater than 20 micrograms/ml) of MLCK in vitro. As a result of diphosphorylation, the actin-activated myosin ATPase activity was increased 3 to 4-fold as compared to the monophosphorylation. (2) Both di- and monophosphorylation reactions showed similar Ca2+, KCl, MgCl2-dependence. Maximal reaction was seen at [Ca2+] greater than 10(-6) M, 60 mM KCl and 2 mM MgCl2. This condition was physiological in activated platelets. (3) Di- and monophosphorylated myosin showed similar Ca2+, KCl-dependence of ATPase activity but distinct MgCl2-dependence. Diphosphorylated myosin showed maximal ATPase activity at 2 mM MgCl2 and monophosphorylated myosin showed a maximum at 10 mM MgCl2. (4) The addition of tropomyosin stimulated actin-activated ATPase activity in both di- and monophosphorylated myosin to the same degree. (5) ML-9, a relatively specific inhibitor of MLCK, inhibited the aggregation of human platelets induced by thrombin ex vivo in a dose-dependent manner. Moreover, this drug also partially inhibited both di- and monophosphorylation reactions and actin-activated ATPase activity. On the other hand, H-7, a synthetic inhibitor of protein kinase C, had little effect on the aggregation of human platelets induced by thrombin ex vivo. From these results, we conclude that diphosphorylation of platelet myosin by MLCK may play an important role in activated platelets in vivo.
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PMID:Diphosphorylation of platelet myosin by myosin light chain kinase. 153 1

1. We tested the hypotheses that coupling between oxidative metabolism and force in noradrenaline (NOR)-activated rabbit aorta is controlled (a) by an energy-dependent step or steps in receptor-operated coupling mechanisms upstream to myosin light chain (MLC) kinase, or (b) by energy limitation of MLC kinase-mediated phosphorylation of the MLC or actin-activated myosin ATPase. 2. Oxidative energy production was rapidly inhibited by decreasing organ bath PO2 to less than 30 mmHg. There was no difference, comparing KCl- or NOR-induced force, in the rates of decrease of [PCr] (phosphocreatine) or [ATP] following inhibition of oxidative energy production. (In this report we use the term [PCr] and [ATP] to indicate mean tissue values). Initial rates of decrease in [PCr] and [ATP] following inhibition of oxidative energy production were 0.05 mM/min and 0.06 mM/min, respectively. 3. Despite similar decreases in mean tissue [PCr] and [ATP], relaxations of KCl-induced contractions following inhibition of oxidative energy production were markedly delayed and were blunted compared to relaxations seen during NOR-induced contractions. The threshold mean tissue [PCr] and [ATP] for relaxation during KCl stimulation were 0.25 and 0.60 to 0.80 mM, respectively. During NOR stimulation, threshold values of [PCr] and [ATP] were 0.50 mM and 0.80 mM, respectively. Mean tissue [PCr] and [ATP] levels at 50% relaxation of KCl-induced force were less than 0.1 mM and 0.1 mM, respectively. Fifty per cent relaxation of NOR-induced force occurred at [PCr] and [ATP] values of 0.35 mM and 0.65 mM, respectively. 4. MLC phosphorylation levels decreased during relaxation of NOR force evoked by inhibition of oxidative energy production. There was no change in the level of MLC phosphorylation following inhibition of oxidative energy production in KCl-contracted muscle even at mean tissue [PCr] and [ATP] lower than values associated with decreases in MLC phosphorylation during relaxations of NOR-induced force. 5. Oxygen-induced redevelopment of force during NOR exposure was not dependent on extracellular Ca2+. Mean tissue [PCr] increased prior to onset of O2-evoked force redevelopment. Increases in MLC phosphorylation were seen at the time of onset of force redevelopment. 6. Oxidative metabolism-contraction coupling during NOR-stimulation seems not to be due to energy limitation of the MLC kinase reaction or actin-activated myosin ATPase. Data suggest the rate-limiting step is an energy-dependent reaction in receptor-operated coupling mechanisms upstream to MLC kinase.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Rate-limiting energy-dependent steps controlling oxidative metabolism-contraction coupling in rabbit aorta. 153 69

Permeabilized endothelial cell monolayers retracted on exposure to ATP and Ca2+. ADP, inosine triphosphate (ITP), GTP, adenosine 5'-(gamma-thio)triphosphate (ATP-gamma S), and 5'-adenylylimidodiphosphate failed to support retraction. However, ATP gamma S, a substrate for myosin light-chain kinase (MLCK) but not myosin adenosinetriphosphatase (ATPase), combined with ITP, a substrate for myosin ATPase but not MLCK, supported retraction. Two MLCK pseudosubstrate peptides, M5 and SM-1, inhibited endothelial cell retraction equally and more effectively than myosin kinase-inhibitory peptide with a sequence based on the phosphorylated site of myosin light chain. M5 was shown to inhibit thiophosphorylation of endothelial cell myosin light chains. Endothelial cells incubated with exogenous unregulated kinase in the presence of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetra-acetic acid retracted on addition of ATP. This retraction was accompanied by thiophosphorylation of the 19 kDa myosin light chains in the presence of ATP gamma 35S. The N-ethylmaleimide-modified subfragment 1 of myosin heads, a specific inhibitor of actin-myosin interaction, prevented retraction. These data add support to the proposal of a central role for MLCK activation of myosin in endothelial retraction.
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PMID:Regulation of permeabilized endothelial cell retraction by myosin phosphorylation. 185 58

The 20-kDa regulatory myosin light chain (MLC), also known as MLC-2, plays an important role in the regulation of both smooth muscle and nonmuscle cell contractile activity. Phosphorylation of MLC-2 by the enzyme MLC kinase increases the actin-activated myosin ATPase activity and thereby regulates the contractile activity. We have isolated and characterized an MLC-2 cDNA corresponding to the human vascular smooth muscle MLC-2 isoform from a cDNA library derived from umbilical artery RNA. The translation of the in vitro synthesized mRNA, corresponding to the cDNA insert, in a rabbit reticulocyte lysate results in the synthesis of a 20,000-dalton protein that is immunoreactive with antibodies raised against purified chicken gizzard MLC-2. The derived amino acid sequence of the putative human smooth muscle MLC-2 shows only three amino acid differences when compared to chicken gizzard MLC-2. However, comparison with the human cardiac isoform reveals only 48% homology. Blot hybridizations and S1 nuclease analysis indicate that the human smooth muscle MLC-2 isoform is expressed restrictively in smooth muscle tissues such as colon and uterus and in some, but not all, nonmuscle cell lines. Previously reported MLC-2 cDNA from rat aortic smooth muscle cells in culture is ubiquitously expressed in all muscle and nonmuscle cells, and it was suggested that both smooth muscle and nonmuscle MLC-2 proteins are identical and are probably encoded by the same gene. In contrast, the human smooth muscle MLC-2 cDNA that we have characterized from an intact smooth muscle tissue is not expressed in skeletal and cardiac muscles and also in a number of nonmuscle cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization and differential expression of human vascular smooth muscle myosin light chain 2 isoform in nonmuscle cells. 252 55

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

The addition of large amounts of myosin light chain kinase to the reconstituted gizzard actomyosin shows diphosphorylation of 20 kDa myosin light chain. Accompanying diphosphorylation, the actin-activated myosin ATPase activity was also enhanced. The extent of diphosphorylation and the myosin ATPase activity were clearly demonstrated to be in a linear relationship. From the time course experiment, the conversion of monophosphorylated light chain into one which was diphosphorylated seemed to be a sequential process. Moreover, analyzing phospho-amino acid by using a two-dimensional electrophoresis technique revealed that monophosphorylated light chain contained phosphoserine and diphosphorylated one contained phosphothreonine in addition to phosphoserine.
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PMID:Linear relationship between diphosphorylation of 20 kDa light chain of gizzard myosin and the actin-activated myosin ATPase activity. 293 11

The purpose of this study was to examine the distribution of myosin isozymes in rodent (Rattus norvegicus) hindlimb skeletal muscles and regions of muscle known to have contrasting fiber-type composition. Muscle samples were analyzed for Ca2+-regulated myofibril adenosine triphosphatase (ATPase) activity, Ca2+-activated myosin ATPase activity, myosin isozyme profile, and myosin light chain profile. Four isozymes of myosin were identified based on native protein and light chain electrophoresis patterns: one associated primarily with slow-twitch muscle (SM) and three associated primarily with fast-twitch muscle (FM). Multiple linear regression analysis of Ca2+-regulated myofibril ATPase activity (pCA 4) vs. measured isozyme profile was used to estimate the myofibril ATPase activities of the individual isozymes (FM1 = 0.86, FM2 = 0.52, FM3 = 0.31, and SM = 0.15 mumol Pi formed . mg myofibril protein-1 . min-1 at 25 degrees C, n = 180, P less than 0.001). Differences in the native isozyme profiles and myofibril ATPase activities between muscles and muscle regions of similar fiber type composition indicate that a given fiber type may not necessarily express a single isozyme profile. These data are consistent with the hypothesis that, among rodent hindlimb skeletal muscles and inherently their motor units, a range of myosin isozyme profiles exists that may provide a broad range of mechanical expression.
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PMID:Myosin isozyme distribution in rodent hindlimb skeletal muscle. 294 6


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