RESUMEN
Interrelation between the effects of C-protein and LC2-light chains on actin-activated ATPase activity of skeletal muscle myosin has been investigated at various ionic strength (0.06-0.14) and free calcium levels (10(-4) M, 10(-8) M). The ATPase activity of AM reconstituted with column-purified myosin or partly-purified myosin and non-regulated actin exhibits a pronounced dependence on ionic strength with maximum at I = 0.1. C-protein impurities (5 per cent) usually present in Minit can inhibit AM ATPase at every ionic strength assayed, without changing the character of this dependence. Actin-activated ATPase of the above myosins shows calcium sensitivity at every ionic strength studied. The partial removal of LC2 from Mcol results in a decrease of AM ATPase and in a disappearance of its calcium sensitivity. C-protein added to Mcol in a molar ratio of 1:1 inhibits considerably AM ATPase, reduces its sensitivity to ionic strength and abolishes its calcium sensitivity.
Asunto(s)
Adenosina Trifosfatasas/metabolismo , Proteínas Portadoras/farmacología , Miosinas/farmacología , Adenosina Trifosfatasas/antagonistas & inhibidores , Animales , Calcio/farmacología , Técnicas In Vitro , Músculos/metabolismo , Concentración Osmolar , ConejosRESUMEN
It is shown that when myosin and heavy (HMM) and light (LMM) meromyosins are treated with concentrated solutions of neutral salts there is change in a number of parameters of the fluorescence spectra of these proteins. For myosin and HMM this change takes place in the region of the same concentrations of LiCl, MgDl2, KSCN where there occurs dissociation of the light chains of the myosin molecule. Change in the fluorescence characteristics of myosin and HMM in the presence of these salts may be caused by two effects: change in the native conformation of the myosin molecule and dissociation of its light chains. The effect of salts on LMM fluorescence is in good agreement with general theory of the influence of concentrated salts on macromolecules.