DIRECTION AND SPEED OF ACTIN-FILAMENTS MOVING ALONG THICK FILAMENTS ISOLATED FROM MOLLUSCAN SMOOTH-MUSCLE

The active movement of fluorescence-labeled actin filaments along thick filaments isolated from molluscan smooth muscle was observed. Along a single thick filament, actin filaments moved toward the center of the thick filament at the speed of 1.19±0.38 μm 8- (mean±SD, n=42) and detached themselves from it upon reaching the central zone. Movement of actin also occurred in the opposite direction, i.e., away from the center, albeit at a much lower velocity (0.09±0.07 μms-1 n = 17). Thus, the thick filament shows functional bipolarity in terms of velocity but does not determine the direction of the movement. © 1990 Copyright, 1990 by the Journal of Biochemistry.