Calcium sensitivity of myofilaments in cardiac muscle--effect of myosin phosphorylation.
We investigated the influence of the extent of phosphorylation of the myosin P-light-chain on the calcium sensitivity of skinned heart fibres. Treatment of skinned heart fibres with PCM-phosphatase decreased the phosphorylation level of P-light-chain from 0.3 mol P/mol LC-2 and 0.2 mol P/mol LC-2* to 0.16 mol P/mol LC-2 and 0.14 mol P/mol LC-2*. Isometric tension development decreased by 34% at submaximal Ca2+-concentration (pCa 5.5) after incubation with PCM-phosphatase while tension achieved at maximum Ca2+-concentration (pCa 4.3) was not affected. The effect of desensitization on skinned fibres could be reversed by washing out the phosphatase or by addition of myosin light chain kinase.
D008841:Actin Cytoskeleton / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D003599:Cytoskeleton / Q000378:metabolism*; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000494:pharmacology; D043263:Myosin-Light-Chain Phosphatase; D009218:Myosins / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D013552:Swine
D009219:Myosin-Light-Chain Kinase; D010749:Phosphoprotein Phosphatases; D043263:Myosin-Light-Chain Phosphatase; D009218:Myosins; D002118:Calcium