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)

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

1. The initial steps on the myosin ATPase (EC 3.6.1.3) pathway are taken to be: (formula; see text) A two-step binding for ATP is assumed, but the evidence for it is unconvincing; because of the rapidity of the process unambiguous values for K1 and K2 are not available. 2. We investigated the myosin mechanism by the chemical flow-quench technique. Reaction mixtures containing [gamma-32P]ATP plus myosin subfragment 1 were quenched in unlabelled ATP (ATP chase) or acid (Pi burst). 3. We show that the ATP-chase method can lead directly to unambiguous values for K1 and k+2. 4. The binding process was slowed down by 40% ethylene glycol. It was studied as a function of the ATP concentration. A limiting plateau resulted, showing a two-step binding for ATP, and values for K1 and k+2 were obtained. 5. K1 and k+2 are rather sensitive to the experimental conditions. Ethylene glycol and lowering of the pH decrease both constants, but an increase in KCl concentration increases them. This suggests that the binding of ATP to myosin is of an electrostatic nature. 6. The Pi-burst method can lead directly to k+3 + k-3, but under certain conditions the kinetics are governed by K1 and k+2. This uncertainty of the interpretation of Pi-burst experiments is discussed.
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PMID:Evidence for the two-step binding of ATP to myosin subfragment 1 by the rapid-flow-quench method. 687 Jul 85