Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.4.1 (myosin ATPase)
 1,140 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The heptapeptide Ile-Arg-Ile-Cys-Arg-Lys-Gly-OEt is the analog of the S-site, one of the actin-binding sites in myosin [Suzuki et al. (1987) J. Biol. Chem. 262, 11410-11412]. Various substituted heptapeptides were synthesized, and the dissociation constants of each acto-heptapeptide complex was measured. Comparison of the dissociation constants indicated that the hydrophobic side chain of Ile-1 was critical for the binding with F-actin, but not that of Ile-3. The positive charge and the side chain length of Arg-2 were also important. The presence of a sulfur atom in the Cys-4 was also necessary. The affinity of the N-terminal Ile-Arg-Ile part for F-actin was influenced by the kind of residues in the C-terminal tetrapeptide part. Based on these results, the side chains of Ile(702), Arg(703), and Cys(SH1)(705) in myosin subfragment-1 heavy chain were assigned to be critical for the binding with F-actin. The amino acid sequence of S-1 heavy chain containing these critical residues for the S-site from residue number 700 to 717 can be predicted as an analogue of the segment B of the ATP-binding site [Walker et al. (1982) EMBO J. 1, 945-951]. The actin-binding S-site possibly shares a part of the ATP-binding site in myosin. We discuss the possibility that the S-site is an inhibitory site of myosin ATPase and the so-called actin-activation of myosin ATPase is a deinhibition induced by transient binding of F-actin to the S-site.
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PMID:Roles of the amino acid side chains in the actin-binding S-site of myosin heavy chain. 214 38

Decameric vanadate (V(10)) inhibits the actin-stimulated myosin ATPase activity, noncompetitively with actin or with ATP upon interaction with a high-affinity binding site (K(i) = 0.27 +/- 0.05 microM) in myosin subfragment-1 (S1). The binding of V(10) to S1 can be monitored from titration with V(10) of the fluorescence of S1 labeled at Cys-707 and Cys-697 with N-iodo-acetyl-N'-(5-sulfo-1-naphthyl)ethylenediamine (IAEDANS) or 5-(iodoacetamido) fluorescein, which showed the presence of only one V(10) binding site per monomer with a dissociation constant of 0.16-0.7 microM, indicating that S1 labeling with these dyes produced only a small distortion of the V(10) binding site. The large quenching of AEDANS-labeled S1 fluorescence produced by V(10) indicated that the V(10) binding site is close to Cys-697 and 707. Fluorescence studies demonstrated the following: (i) the binding of V(10) to S1 is not competitive either with actin or with ADP.V(1) or ADP.AlF(4); (ii) the affinity of V(10) for the complex S1/ADP.V(1) and S1/ADP.AlF(4) is 2- and 3-fold lower than for S1; and (iii) it is competitive with the S1 "back door" ligand P(1)P(5)-diadenosine pentaphosphate. A local conformational change in S1 upon binding of V(10) is supported by (i) a decrease of the efficiency of fluorescence energy transfer between eosin-labeled F-actin and fluorescein-labeled S1, and (ii) slower reassociation between S1 and F-actin after ATP hydrolysis. The results are consistent with binding of V(10) to the Walker A motif of ABC ATPases, which in S1 corresponds to conserved regions of the P-loop which form part of the phosphate tube.
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PMID:Decavanadate binding to a high affinity site near the myosin catalytic centre inhibits F-actin-stimulated myosin ATPase activity. 1512 21