Further studies on the effects of myosin P-light chain phosphorylation on contractile properties of skinned cardiac fibres.
We investigated the influence of myosin P-light chain phosphorylation by Ca2+-calmodulin dependent myosin light chain kinase (MLCK) on the sensitivity of the tension-pCa relation and maximum unloaded shortening velocity (Vmax) of chemically skinned heart fibres of the pig. Submaximum Ca2+ stimulation (pCa 5.5) induced 20 +/- 5% of the isometric tension achieved at maximum Ca2+ activation (pCa 4.3). MLCK-induced myosin P-light chain phosphorylation increased the isometric force development at pCa 5.5 by 40% whereas maximum tension at pCa 4.3 was not affected. Unloaded shortening velocity (Vmax) was not altered by myosin P-light chain phosphorylation either at maximum or at submaximum Ca2+ concentration, being c. 1.2 muscle length/s at pCa 5.5 and 2.2 muscle length/s at pCa 4.3. The MLCK-induced increase of the myosin P-light chain phosphorylation level was evaluated by determination of 32P-incorporation. Two phosphorylatable myosin P-light chains could be demonstrated.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000494:pharmacology; D007700:Kinetics; D009200:Myocardial Contraction; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D013552:Swine
D002147:Calmodulin; D010761:Phosphorus Radioisotopes; D009219:Myosin-Light-Chain Kinase; D009218:Myosins; D002118:Calcium