平滑肌肌球蛋白B的超沉淀与肌球蛋白轻链磷酸化

The Superprecipitation of Smooth Muscle Myosin B and Ca^(2+) CaM-Dependent Phosphorylation of the Myosin Light Chain

本文报导了牛胃肌球蛋白B(天然肌动球蛋白)的超沉淀性质。当钙离子、钙调蛋白和ATP存在时,肌球蛋白B出现超沉淀,在pH6.8和7.5处,有两个峰值。Ca^(2+)(PCa值8-4)对超沉淀影响的浓度-反应曲线呈典型的S形,表明当Ca^(2+)浓度处于微摩尔水平时产生超沉淀。伴随超沉淀发生了肌球蛋白调节轻链磷酸化。这说明肌球蛋白轻链的Ca^(2+)-CaM依赖性磷酸化可能包含在脊椎动物平滑肌收缩活动的调节机制中。

The characteristics of superprecipitation of myosin B (natural actomyosin) from bovine stomach has been studied.It was found that the superprecipitation of myosin B occurs in the presence of calcium, calmodulin and ATP, showing two peaks at pH 6.8 and 7.5 The concentration-response curve for the effect of Ca2+(pCa values, from 8 to 4) on superprecipitation appears in typical S-form, indicating that myosin B superprecipitation occurs at Ca2+ concentration of micromolar level.The phosphorylation of myosin light chain is accompanied by superprecipitation.It is suggested that the Ca2+ -CaM-dependent phosphorylation of myosin light chain might be involved in the regulatory mechanism of contraction in vertebrate smooth muscle.