Effect of caldesmon on the ATPase activity and the binding of smooth and skeletal myosin subfragments to actin.

摘要: We have previously shown that inhibition of the ATPase activity skeletal muscle myosin subfragment 1 (S1) by caldesmon is correlated with S1 binding in presence ATP or pyrophosphate (Chalovich, J., Cornelius, P., and Benson, C. (1987) J. Biol Chem. 262, 5711-5716). In contrast, Lash et al. (Lash, Sellers, Hathaway, D. (1986) Biol. 261, 16155-16160) smooth heavy meromyosin (HMM) an increase HMM to actin ATP. now show, agreement, does actin-tropomyosin while decreasing activity. The effect on reversed Ca2+-calmodulin. Caldesmon strengthens S1.ATP HMM.ATP but a lesser extent than HMM.ATP. Furthermore, this not parallel absence ATP, all subfragments compete for actin. Thus, has depends source myosin, type subfragment, nucleotide present. actin-activated hydrolysis caldesmon, however, greatly different subfragments. Evidence presented inhibits attenuating productive interaction between normally accelerates hydrolysis. increased seen some subfragments, may be due these nonproductive site actin-caldesmon. which show appear bind directly as demonstrated affinity chromatography.