Calmodulin and myosin light-chain kinase of rabbit fast skeletal muscle.
1. It is confirmed that myosin light-chain kinase is a protein of mol.wt. about 80,000 that is inactive in the absence of calmodulin. 2. In the presence of 1 mol of calmodulin/mol of kinase 80-90% of the maximal activity is obtained. 3. Crude preparations of the whole light-chain fraction of rabbit fast-skeletal-muscle myosin contain enough calmodulin to activate the enzyme. A method for the preparation of calmodulin-free P light chain is described. 4. A procedure is described for the isolation of calmodulin from rabbit fast skeletal muscle. 5. Rabbit fast-skeletal-muscle calmodulin is indistinguishable from bovine brain calmodulin in its ability to activate myosin light-chain kinase. The other properties of these two proteins are also very similar. 6. Rabbit fast-skeletal-muscle troponin C was about 10% as effective as calmodulin as activator for myosin light-chain kinase. 7. By chromatography on a Sepharose-calmodulin affinity column evidence was obtained for the formation of a Ca2+-dependent complex between calmodulin and myosin light-chain kinase. 8. Troponin I from rabbit fast skeletal muscle and histone IIAS were phosphorylated by fully activated myosin light-chain kinase at about 1% of the rate of the P light chain.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D009132:Muscles / Q000201:enzymology*; D009218:Myosins; D010770:Phosphotransferases / Q000378:metabolism*; D011817:Rabbits; D013379:Substrate Specificity
D002147:Calmodulin; D002352:Carrier Proteins; D010770:Phosphotransferases; D009218:Myosins; D002118:Calcium