Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Myosin modified in the presence or in the absence of pyrophosphate by 2,4-dinitrophenyl beta-hydroxyethyl disulphide was treated with iodo[1-(14)C]acetamide. The residual Ca(2+)-stimulated adenosine triphosphatase (ATPase) activity of the modified myosin was different depending on the presence or absence of PP(i) during modification and the number of 2,4-dinitrophenyl beta-hydroxyethyl disulphide-modified thiol groups. The radioactivity incorporated into the light components of myosin correlated with the Ca(2+)-stimulated ATPase activity of the modified myosin and decreased with decreasing residual Ca(2+)-stimulated ATPase activity of the modified myosin. When native myosin was treated with low concentrations of iodo[1-(14)C]acetamide the residual Ca(2+)-stimulated ATPase activity of carboxyamidomethylated myosin was high and the radioactivity incorporated into the light components of myosin was negligible. The thiol groups of the light components of myosin are essential to preserve the ATPase activity of the protein and are close to the pyrophosphate-binding sites.
 ...
PMID:The location of the thiol groups of myosin that are protected by pyrophosphate against reaction with 2,4-dinitrophenyl -hydroxyethyl disulphide. 433 36

The steady-state kinetics of the K+, Ca2+, and Mg2+-activated adenosine triphosphatase (ATPase) activities of rabbit skeletal myosin were investigated in the substrate concentration range from 0.05 microM to 5 mM and found not to follow Michaelis-Menten kinetics but rather to display biphasic behavior. The Ca2+-ATPase activity of myosin chymotryptic subfragment-1 (S-1), which has only one active site, also exhibits biphasic kinetics, thus excluding the possibility that the biphasic behavior is caused by negative cooperativity between the two active sites of myosin. Myosin K+ and Mg2+-ATPase are both activated by 5'-adenyl methylenediphosphonate (AdoPP[CH2]P) in a competitive manner at high substrate concentrations; i.e. the maximal velocity observed at high substrate concentrations is independent of the AdoPP[CH2]P concentration. This result provides evidence for substrate activation via binding to a regulatory site. Pyrophosphate inhibits myosin ATPase in a competitive manner at low substrate concentrations and in an uncompetitive manner at high substrate concentrations, with the uncompetitive Ki being smaller than the competitive Ki; i.e. pyrophosphate binds more tightly to the effector site than to the active site.
 ...
PMID:Biphasic steady-state kinetics of myosin adenosine triphosphatase. Evidence for a substrate effector site. 610 32

Myosin was isolated from the free right and left ventricular wall of normal adult human myocardium and purified until actin contamination was considered negligible as judged by sodium dodecyl sulphate polyacrylamide gel electrophoresis and adenosine triphosphatase assay in the presence of magnesium chloride. Ca2+ and K+ ethylenediaminetetra-acetic acid activated adenosine triphosphatase activities were determined in the presence of 3 mmol.litre-1 adenosine triphosphate. Myosin light chain subunits, VLC-1 and VLC-2, were analysed by polyacrylamide gel electrophoresis using: (i) sodium dodecyl sulphate at pH 7.0; (ii) 6 mol.litre-1 urea at pH 8.5; and (iii) isoelectric focusing in 9.2 mol.litre-1 urea over the pH range 4 to 6. No inherent differences in enzymic or physiochemical properties of the myosins from the human right and left ventricle were observed. Similar results were obtained in the baboon and dog.
 ...
PMID:Myosin adenosinetriphosphatase activity and light chain subunit composition of human right and left ventricle. 645 7

Myosin II, which converts the energy of adenosine triphosphate hydrolysis into the movement of actin filaments, is a hexamer of two heavy chains, two essential light chains, and two regulatory light chains (RLCs). Dictyostelium myosin II is known to be regulated in vitro by phosphorylation of the RLC. Cells in which the wild-type myosin II heavy chain was replaced with a recombinant form that lacks the binding site for RLC carried out cytokinesis and almost normal development, processes known to be dependent on functional myosin II. Characterization of the purified recombinant protein suggests that a complex of RLC and the RLC binding site of the heavy chain plays an inhibitory role for adenosine triphosphatase activity and a structural role for the movement of myosin along actin.
 ...
PMID:A functional recombinant myosin II lacking a regulatory light chain-binding site. 826 74

The relationship between the myosin heavy chain (HC) IId isoform and histochemically defined fibre types was investigated in the rat soleus muscle after hindlimb suspension. After 4 weeks of suspension, right and left muscles were removed and fibre type composition and total fibre number were examined by histochemical myosin adenosine triphosphatase staining sections. Myosin HC isoforms were analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. After the suspension, there was a significant decrease in the percentage of type I fibres and a concomitant increase in that of type IIa fibres. However, the total number of fibres was not affected by suspension. The synthesis of HC IId isoform, which was not found in the control, and the decrease in the ratio of slow type myosin heavy chain isoform (HC I) were observed after suspension. These results would may suggest that the change of fibre type composition was caused by a shift from type I to IIa fibres after suspension. Furthermore, it could be suggested that the synthesis of HC IId isoform occurred during the stage of type shift from type I to IIa fibres.
 ...
PMID:Relationship between myosin heavy chain IId isoform and fibre types in soleus muscle of the rat after hindlimb suspension. 833 Jun 15

Myosin is one of the basic structural components of skeletal muscles. Its interaction with actin results in muscle contraction. The myosin molecule is composed of two heavy (MyHC) and two light chains (MyLC) that, together with the adenosine triphosphatase (ATPase) activity, determine the functional characteristics of the fibre. Both MyHC and MyLC present different isoforms. The main MyHC isoforms in adult mammals are the slow MyHC (MyHC-I) and fast MyHCs (MyHC-IIa, MyHC-IIb and MyHC-IIx). Muscle fibres can express only one isoform or coexpress different forms. The muscle phenotype is the product of genome plus environmental stimuli. The family of genes that codifies the MyHC isoforms is located in two different clusters, each isoform being encoded by a separate gene. The gene corresponding to slow MyHC is located in chromosome 14, both in humans and in mice. The other genes are positioned in chromosome 17 in humans, and in chromosome 11 in mice. The transcriptional and translational mechanisms that control the expression of MyHC isoforms are not well known, although it is believed that the main regulation is dependent on mechanical signals. These signals are probably mediated by a biochemical messenger. As a general rule, fast MyHC genes seem to be expressed "by default", whereas the slow MyHC gene would be expressed as a response to changes in load. So far, few studies have analysed the in vivo regulation of MyHC gene expression in respiratory muscles. It has recently been reported that breathing against moderate levels of inspiratory resistance quickly induces an increase in the genetic expression of slow MyHC in the diaphragm. This suggests the possibility of eliciting a phenotypic adaptation of respiratory muscles using specific training protocols.
 ...
PMID:Myosin gene expression in the respiratory muscles. 938 72

Myosin II motors play several important roles in a variety of cellular processes, some of which involve active assembly/disassembly of cytoskeletal substructures. Myosin II motors have been shown to function in actin bundle turnover in neuronal growth cones and in the recycling of actin filaments during cytokinesis. Close examination had shown an intimate relationship between myosin II motor adenosine triphosphatase activity and actin turnover rate. However, the direct implication of myosin II in actin turnover is still not understood. Herein, we show, using high-resolution cryo-transmission electron microscopy, that myosin II motors control the turnover of actin bundles in a concentration-dependent manner in vitro. We demonstrate that disassembly of actin bundles occurs through two main stages: the first stage involves unbundling into individual filaments, and the second involves their subsequent depolymerization. These evidence suggest that, in addition to their "classical" contractile abilities, myosin II motors may be directly implicated in active actin depolymerization. We believe that myosin II motors may function similarly in vivo (e.g., in the disassembly of the contractile ring by fine tuning the local concentration/activity of myosin II motors).
 ...
PMID:A cytoskeletal demolition worker: myosin II acts as an actin depolymerization agent. 1802 3

Muscle lesions and decreased numbers of peripheral nerve branches have been reported in the soft palates of dogs presenting with brachycephalic airway obstruction syndrome (BAOS). Myosin adenosine triphosphatase staining was employed to investigate whether muscle lesions in the elongated soft palate (ESP) of dogs with BAOS reflect the presence of denervation. Soft palates were collected from nine brachycephalic dogs during surgical intervention for BAOS and from five healthy beagle dogs as controls. In the control soft palates, myofibres with relatively uniform diameters and a random mosaic pattern of type I and II myofibres were observed in the palatinus muscle (PM), while almost all of the myofibres in the levator veli palatini muscle (LVPM) were of type II. In the ESPs, small group atrophy, large group atrophy and angular-shaped atrophy were observed in myofibres of the PM and rarely in the LVPM. Fibre type grouping and an increase in type IIC myofibres were found only in the PM. Morphometric analysis of ESPs revealed a significant increase in the number of type I and II myofibres in the PM showing atrophy or hypertrophy compared with controls. A significant increase in atrophic type II myofibres was found in the LVPM of affected dogs. Myopathy consistent with denervation was observed in the PM, but rarely in the LVPM, of ESP specimens. The results suggest that the myopathy seen in dogs with ESP may partly reflect atrophy of myofibres resulting from damage to peripheral nerve branches, with subsequent reinnervation of myofibres.
...
PMID:Denervation-Associated Change in the Palatinus and Levator Veli Palatini Muscles of Dogs with Elongated Soft Palate. 2742 2


<< Previous 1 2