Smooth muscle regulation

肌球蛋白轻链激酶（Myosin light chain kinase， MLCK）是一种平滑肌收缩调节蛋白，通过磷酸化20 kda的肌球蛋白轻链（Myosin light chain, MLC20）激活肌球蛋白atp酶活性。尽管这种作用模式已经确立，但有许多报道称，平滑肌收缩与MLC20磷酸化无关。磷酸化的激酶活性位于MLCK的中心部分，在其N端也具有肌动蛋白结合活性，在其C端也具有肌球蛋白结合活性。本研究显示了MLCK的这种多功能特性是如何改变肌动蛋白-肌球蛋白相互作用的，并提出了我们的观察，即磷酸化在诱导平滑肌收缩时不是强制性的。

Myosin light chain kinase (MLCK) is a regulatory protein for smooth muscle contraction, which acts by phosphorylating 20-kDa myosin light chain (MLC20) to activate the myosin ATPase activity. Although this mode of action is well-established, there are numerous reports of smooth muscle contraction that is not associated with MLC20 phosphorylation. The kinase activity for the phosphorylation is localized at the central part of MLCK, which is also furnished with actin-binding activity at its N terminal and myosin-binding activity at its C terminal. The present study shows how such multifunctional properties of MLCK modify the actin-myosin interaction and presents our observations that the phosphorylation is not obligatory in induction of smooth muscle contraction.