Conversion of a Ca2+-dependent myosin light chain kinase from skeletal muscle to a Ca2+-independent form.
The Ca2+- and calmodulin-dependent myosin light chain kinase of rabbit skeletal muscle was converted to a Ca2+-independent form by limited proteolysis with alpha-chymotrypsin. The conditions prevailing during proteolysis are important and the loss of Ca2+-dependence was achieved best by hydrolysis of the Ca2+-calmodulin-kinase complex. The lack of Ca2+- and calmodulin-dependence was found using both myosin and isolated light chains as substrates. The specific activity of the Ca2+-independent form (Mr approximately 65,000) was similar to that of the native enzyme, i.e., 2 to 5 mumol phosphate transferred min-1 mg-1 kinase. The 65,000-dalton fragment was phosphorylated by the catalytic subunit of the cAMP-dependent protein kinase and approximately 0.8 moles phosphate were incorporated per fragment.
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002147:Calmodulin; D055598:Chemical Phenomena; D002621:Chemistry; D002918:Chymotrypsin; D006868:Hydrolysis; D009132:Muscles / Q000201:enzymology*; D009219:Myosin-Light-Chain Kinase; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011817:Rabbits
D002147:Calmodulin; D011494:Protein Kinases; D009219:Myosin-Light-Chain Kinase; D002918:Chymotrypsin; D002118:Calcium