The influence of P-light chain phosphorylation by myosin light chain kinase on the calcium sensitivity of chemically skinned heart fibres.

Phosphorylation of the P-light chain of myosin might be involved in the regulation of cardiac contractility. Thus an enhanced phosphorylation level of the P-light chain catalyzed by Ca2+-calmodulin-dependent myosin light chain kinase (MLCK) increased significantly the Ca2+ sensitivity of chemically skinned ventricular fibre bundles of the pig. This effect was reversible. Whereas force development at submaximal Ca2+ concentration (pCa 5.5) increased by approximately 50% in the presence of MLCK, maximum tension achieved at maximum Ca2+-concentration (pCa 4.3) was not affected.