[ATPase and regulatory properties of skeletal muscle myosin in Citellus undulatus susliks during various stages of winter hibernation].

The paper is devoted to the study on enzymatic and regulatory properties of skeletal muscle myosin of hibernating ground squirrels (Citellus undulatus) for the purpose of elucidating the contribution of myosin and myosin filaments to the change of physiological state of the animal at the different stages of hibernation (hibernation, arousing, winter activity). It has been revealed that actin-activated ATPase activity of myosins of hibernating and arousing ground squirrels is less by 60 and 20%, correspondingly, than that of the myosin of active animals. In the absence of troponin-tropomyosin complex the Ca(2+)-sensitivity of actomyosins of the hibernating and arousing ground squirrels is less by 60 and 55%, correspondingly, than that of the actomyosin of active animals. The results obtained by us point to the essential decrease of functional properties of the main contractile protein, myosin upon hibernation, which evidently contributes to the inhibition of moving capacity of skeletal muscles at this period.