Truebestein Linda, Elsner Daniel J, Fuchs Elisabeth, Leonard Thomas A
Department of Structural and Computational Biology, Max F. Perutz Laboratories, Vienna Biocenter, 1030 Vienna, Austria.
Department of Medical Biochemistry, Medical University of Vienna, 1090 Vienna, Austria.
Nat Commun. 2015 Dec 1;6:10029. doi: 10.1038/ncomms10029.
The Rho-associated coiled-coil kinases (ROCK) are essential regulators of the actin cytoskeleton; however, the structure of a full-length ROCK is unknown and the mechanisms by which its kinase activity is controlled are not well understood. Here we determine the low-resolution structure of human ROCK2 using electron microscopy, revealing it to be a constitutive dimer, 120 nm in length, with a long coiled-coil tether linking the kinase and membrane-binding domains. We find, in contrast to previous reports, that ROCK2 activity does not appear to be directly regulated by binding to membranes, RhoA, or by phosphorylation. Instead, we show that changing the length of the tether modulates ROCK2 function in cells, suggesting that it acts as a molecular ruler. We present a model in which ROCK activity is restricted to a discrete region of the actin cytoskeleton, governed by the length of its coiled-coil. This represents a new type of spatial control, and hence a new paradigm for kinase regulation.
Rho相关卷曲螺旋激酶（ROCK）是肌动蛋白细胞骨架的重要调节因子；然而，全长ROCK的结构尚不清楚，其激酶活性的调控机制也未得到充分了解。在此，我们利用电子显微镜确定了人类ROCK2的低分辨率结构，发现它是一种组成型二聚体，长度为120纳米，有一个长的卷曲螺旋连接激酶和膜结合结构域。与之前的报道相反，我们发现ROCK2的活性似乎不受与膜、RhoA结合或磷酸化的直接调控。相反，我们表明改变连接体的长度可调节细胞中ROCK2的功能，这表明它起到了分子尺的作用。我们提出了一个模型，其中ROCK活性被限制在肌动蛋白细胞骨架的一个离散区域，由其卷曲螺旋的长度控制。这代表了一种新型的空间控制，因此也是激酶调控的一种新范式。
