IN-VITRO INTERACTIONS OF PROTEINS FROM IN SECT MYOSIN-FILAMENTS

Thick filaments or insect muscles contain at least 2 myosin-associated proteins, paramyosin and projectin. In vitro, both proteins seem to c ooperate with respect to the determination of the dimensions of synthe tic cofilaments (formed by coaggregation of the 3 proteins) and to the stimulation of their actin-activated ATPase activity. Projectin from locust muscles may phosphorylate in vitro itself and myosin heavy chai ns. Results of binding studies suggest that there are different bindin g affinities between the three proteins myosin, paramyosin and project in. These properties might influence the process of filament formation during muscle development and, by an improved presentation of the myo sin heads at the filament surface, also improve the efficiency of the contractile system.