Inhibition of acto-myosin subfragment-1 ATPase activity by peptides corresponding to various segments of the 20-kDa domain of myosin heavy chain.
As reported previously, the synthetic heptapeptide having the amino acid sequence around the reactive Cys (SH1) of myosin heavy chain, IRICRKG-NH2, inhibited acto-myosin subfragment-1 (S-1) ATPase activity and half inhibition (K1/2) was observed at a peptide concentration of 0.06 mM. The inhibitory ability of the peptide was found to be decreased to one-fifth by acetylation of its N-terminal alpha-amino group. A similar effect of N-acetylation was observed with a nonapeptide, EGIRICRKG-NH2, and an undecapeptide, VLEGIRICRKG-NH2. These results indicate that N-terminal-free synthetic peptides do not act as proper analogs of the corresponding segment of S-1 heavy chain against F-actin. We isolated a longer peptide extending from Thr682 to Lys709 in S-1 heavy chain, with two Cys residues corresponding to SH1 and SH2. This peptide, having 28 residues (28peptide), inhibited acto-S-1 ATPase activity with a K1/2 of 0.23 mM. A cosedimentation binding assay indicated that the 28peptide completely dissociated acto-S-1 in the presence of ATP. This behavior is different from that observed with the N-terminal-free synthetic heptapeptide, and thus the 28peptide might be an analog of the corresponding segment. There is a possibility that the region corresponding to the 28peptide in S-1 heavy chain may bind directly with F-actin and may be involved in determining the acto-S-1 link during the steady state of the acto-S-1 ATPase reaction.
Eto
M
M
Department of Chemistry, Faculty of Science, Hokkaido University.
Isonishi
K
K
Fukui
Y
Y
Morita
F
F
Nishi
N
N
Tokura
S
S
D000107:Acetylation; D000255:Adenosine Triphosphate / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009218:Myosins / Q000037:antagonists & inhibitors* / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D011817:Rabbits
D010455:Peptides; D000255:Adenosine Triphosphate; D009218:Myosins