Association of Myosin to Form Contractile Systems

Abstract

The association of myosin molecules at low ionic strength to form filamentous structures similar in general topology to the thick filaments of muscle has been under study in several laboratories in recent years (Jakus and Hall, 1947; Noda and Ebashi, 1960; Zobel and Carlson, 1963; Huxley, 1963; Kaminer and Bell, 1966a, b; Josephs and Harrington, 1966, 1968). Electron micrographs of negatively stained preparations of these macro-structures, prepared by lowering the ionic strength of myosin solutions near neutral pH, reveal particles of 100–150 Å diameter, with irregular surface projections except for a transverse zone devoid of such corrugations of about 0.15-0.2 µ in width which is always situated near the center of the filament. Under these ionic conditions, Huxley (1963) found the lengths of filament particles to vary between 0.25 and 2 µ with a mean length near 1.2 µ. Filaments generated by dialysis near pH 8 have similar structural properties...