J. Biol. Chem., Vol. 265, Issue 9, 4939-4943, 03, 1990
Inhibition of actomyosin subfragment 1 ATPase activity by analog peptides of the actin-binding site around the Cys(SH1) of myosin heavy chain
R Suzuki, F Morita, N Nishi and S Tokura
Department of Chemistry, Faculty of Science, Hokkaido University, Japan.
The synthetic heptapeptide, Ile-Arg-Ile-Cys-Arg-Lsy-Gly-ethoxy, an analog
of one of the actin binding sites on myosin head (S-site) (Suzuki, R.,
Nishi, N., Tokura, S., and Morita, F. (1987) J. Biol. Chem. 262,
11410-11412) was found to completely inhibit the acto-S-1 (myosin
subfragment 1) ATPase activity. The effect of the heptapeptide on the
binding ability of S-1 for F-actin was determined by an ultracentrifugal
separation. Results indicated that the heptapeptide scarcely dissociated
the acto-S-1 complex during the ATPase reaction. Consistent results were
obtained from the acto-S-1 ATPase activities determined as a function of
S-1 concentrations in the absence or presence of the heptapeptide at a
fixed F-actin concentration. The heptapeptide reduced the maximum acto-S-1
ATPase activity without affecting the apparent dissociation constant of the
acto-S-1 complex. The heptapeptide bound by a site on actin complementary
to the S-site probably inhibits the activation of S-1 ATPase by F-actin.
These results suggest that S-1 ATPase is necessary to rebind transiently
with F-actin at the S-site in order to be activated by F-actin. This is
consistent with the activation mechanism proposed assuming the two
actin-binding sites on S-1 ATPase (Katoh, T., and Morita F. (1984) J.
Biochem. (Tokyo) 96, 1223-1230).
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