Myosin light chain kinase stimulates smooth muscle myosin ATPase activity by binding to the myosin heads without phosphorylating the myosin light chain
Myosin light chain kinase stimulates smooth muscle myosin ATPase activity by binding to the myosin heads without phosphorylating the myosin light chain
复制标题
DOI：
10.1016/s0006-291x(03)00690-9
复制
发表时间：
2003-05-23
影响因子：
3.1
通讯作者：
Kohama, K
中科院分区：
文献类型：
--
作者：
Gao, Y;Kawano, K;Kohama, K
肌球蛋白轻链激酶（MLCK）是平滑肌收缩的多功能调节蛋白[IUBMB Life 51（2001）337，用于综述]。其公认的调节模式是磷酸化20 kDa肌球蛋白轻链（MLC 20）以激活肌球蛋白ATP酶活性。MLCK除了具有这种激酶活性外，还具有肌球蛋白结合活性。肌球蛋白结合活性还刺激肌球蛋白ATP酶活性而不磷酸化MLC 20 [Proc.Natl. Acad. Sci. USA 96（1999）6666]。我们设计了一个含有肌球蛋白结合结构域但没有催化结构域的MLCK片段，以探索肌球蛋白如何被这种非激酶途径刺激。由此获得的重组片段刺激肌球蛋白ATP酶活性，V-max = 5.53 +/- 0.63-倍，K-m = 4.22 +/- 0.58 μ M（n = 4）。通过测定HMM和S1的ATP酶活性，获得了相似的刺激图。还验证了该片段与HMM和S1的结合，表明该片段通过肌球蛋白头发挥刺激作用。由于S1处于活性形式而不管MLC 20的磷酸化状态，我们得出结论，非激酶刺激独立于肌球蛋白激活的磷酸化模式。(C)2003 Elsevier Science（美国）。All rights reserved.
Myosin light chain kinase (MLCK) is a multifunctional regulatory protein of smooth muscle contraction [IUBMB Life 51 (2001) 337, for review]. The well-established mode for its regulation is to phosphorylate the 20 kDa myosin light chain (MLC 20) to activate myosin ATPase activity. MLCK exhibits myosin-binding activity in addition to this kinase activity. The myosin-binding activity also stimulates myosin ATPase activity without phosphorylating MLC 20 [Proc. Natl. Acad. Sci. USA 96 (1999) 6666]. We engineered an MLCK fragment containing the myosin-binding domain but devoid of a catalytic domain to explore how myosin is stimulated by this non-kinase pathway. The recombinant fragment thus obtained stimulated myosin ATPase activity by V-max = 5.53 +/- 0.63-fold with K-m = 4.22 +/- 0.58 muM (n = 4). Similar stimulation figures were obtained by measuring the ATPase activity of HMM and S1. Binding of the fragment to both HMM and S1 was also verified, indicating that the fragment exerts stimulation through the myosin heads. Since S I is in an active form regardless of the phosphorylated state of MLC 20, we conclude that the non-kinase stimulation is independent of the phosphorylating mode for activation of myosin. (C) 2003 Elsevier Science (USA). All rights reserved.