BIDIRECTIONAL MOVEMENT OF ACTIN-FILAMENTS ALONG LONG BIPOLAR TRACKS OF ORIENTED RABBIT SKELETAL-MUSCLE MYOSIN MOLECULES

In actomyosin in vitro motility assays, orientation of myosin molecule s affects their interaction with actin, We obtained long tracks of myo sin molecules with uniform orientation, Bipolar filaments about 50 mu m long were made from myosin rod prepared from molluscan smooth muscle s, to which rabbit skeletal-muscle myosin bound, creating long synthet ic thick-filaments. Movement of F-actin toward their center was much f aster (4.7 +/- 0.6 mu m s(-1)) than in the opposite direction (1.9 +/- 0.2 mu m s(-1)), indicating that myosin molecules were arranged in th e same orientation along each half of the bipolar filament. These comp lex thick-filaments permit measurement of actin movement over 20 mu m of oriented skeletal myosin tracks facilitating mechanistic studies of actomyosin motility. (C) 1997 Federation of European Biochemical Soci eties.