[Influence of C-protein on mechano-chemical properties and structure of reconstituted actomyosin].

C-protein on the mechano-chemical properties (ATPase activity and superprecipitation) of actomyosin systems has been investigated. The presence of C-protein in AM-complexes has been shown to decrease the rate of superprecipitation (SPP) and simultaneously increase the ATPase activity. Both effects of C-protein are dependent on its quantity in the system. Tropomyosin decreased considerably but does not eliminate completely the inhibitory influence of C-protein on the SPP. Electron microscopy does not reveal considerable structural differences in the initial AM-complexes depending on the presence or absence of C-protein. It is supposed that the discovered effects of C-protein on the behaviour of AM-systems are determined by the fine local structural and (or) charge changes produced by C-protein in the region of myosin cross-bridges, which in its turn results in a modification of the actin-myosin interaction. Possible participation of C-protein in the regulation of the interaction of thin and thick filaments in the muscle is discussed.