ACTIN MAY CONTRIBUTE TO THE POWER STROKE IN THE BINARY ACTOMYOSIN SYSTEM

At the physiological protein osmotic pressure, the angle formed betwee n the long axis of the actin monomer and the pointed end of the filame nt axis is roughly 61 degrees in F-actin and about 90 degrees in the m yosin subfragment 1 - decorated F-actin. ?his implies that, in the cou rse of the contractile cycle, actin itself contributes, by about 4 nm, to the displacement of the actin filament toward the center of the sa rcomer. (C) 1994 Academic Press, Inc.