Phosphorylation of cardiac myosin light chain 2 by protein kinase C and myosin light chain kinase increases Ca(2+)-stimulated actomyosin MgATPase activity.
Myosin light chain 2 (MLC2) phosphorylation in rat cardiac whole myosin by cardiac myosin light chain kinase (MLCK) or by protein kinase C (PKC) resulted in increased actin-stimulated myosin MgATPase activity. The phosphorylation also increased Ca(2+)-stimulated myofibrillar MgATPase activity upon substitution of the phosphorylated myosin into myofibrils. In addition, phosphorylation of MLC2 in myofibrils by MLCK increased both the Ca(2+)-sensitivity and maximum activity of the myofibrillar Ca(2+)-stimulated MgATPase activity. The latter effect was inhibited by PKC-phosphorylation of troponin I, troponin T and C-protein. A role for both PKC and MLCK in regulating cardiac myofibrillar activity, via phosphorylation of various contractile proteins, is indicated.
Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322.
T A
TA
Noland
J F
JF
Kuo
D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D004789:Enzyme Activation; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats
D011493:Protein Kinase C; D017301:Ca(2+) Mg(2+)-ATPase; D009218:Myosins; D002118:Calcium