Steady-state force velocity relation of ATP-dependent sliding between slime mold myosin, arranged on paramyosin filaments, and algal cell actin cables

摘要

To investigate characteristics of ATP-dependent sliding of a non-muscle cell myosin, obtained from a cellular slime mold Dictyostelium discoideum, on actin filament, we prepared hybrid thick filaments, in which Dictyostelium myosin was regularly arranged around paramyosin filaments obtained from a molluscan smooth muscle. A single to a few hybrid filaments were attached to a polystyrene bead (diameter, 4.5 mu m; specific gravity, 1.5), and the filaments were made to slide on actin filament arrays (actin cables) in the internodal cell of an alga Chara corallina, mounted on the rotor of a centrifuge microscope. The filament-attached bead was observed to move with a constant velocity under a constant external load for many seconds. The steady-state force-velocity relation of Dictyostelium myosin sliding on actin cables was hyperbolic in shape except for large loads < 0.7-0.8 P-0, being qualitatively similar to that of skeletal muscle fibres, despite a considerable variation in the number of myosin molecules interacting with actin cables. Comparison of the P-V curves between Dictyostelium myosin and muscle myosins sliding on actin cables suggests that the time of attachment to actin in a single attachment-detachment cycle is much longer in Dictyostelium myosin than in muscle myosins. (C) 1998 Elsevier Science Inc. All rights reserved. [References: 23]