The structure of the actin-smooth muscle myosin motor domain complex in the rigor state
The structure of the actin-smooth muscle myosin motor domain complex in the rigor state
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DOI：
10.1016/j.jsb.2017.10.003
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发表时间：
2017-12-01
影响因子：
3
通讯作者：
Taylor, Kenneth A.
中科院分区：
文献类型：
--
作者：
Banerjee, Chaity;Hu, Zhongjun;Taylor, Kenneth A.
基于肌球蛋白的运动利用 ATP 的催化来驱动 F-肌动蛋白和肌球蛋白的相对滑动。最早的基于冷冻电子显微镜 (cryoEM) 和 X 射线晶体学的详细模型假设，较高的肌动蛋白亲和力和杠杆臂运动与被称为肌动蛋白结合裂口的肌球蛋白头部特征的闭合相结合。此后的几项研究使用肌球蛋白-V 的晶体学和 F-肌动蛋白结合的肌球蛋白-I、-II 和-V 的冷冻电镜结构提供了该模型的详细信息。平滑肌肌球蛋白 II 与 F-肌动蛋白的相互作用可能与横纹肌和非肌肉肌球蛋白 II 的相互作用不同，部分原因是重要表面环的长度不同。在这里，我们报告了使用直接电子探测器记录的图像，用无核苷酸重组平滑肌肌球蛋白-II 运动结构域 (MD) 装饰的 F-肌动蛋白的类似 6 A 分辨率重建。 F-肌动蛋白和肌动蛋白-肌球蛋白界面的分辨率最高 (3.5-4 A)，MD 最大半径部分的分辨率最低（类似于 6-7 A）。 F-肌动蛋白密度中内置的原子模型与之前报道的兔肌肉肌动蛋白的原子模型相当，并显示了结合 ADP 的密度。 MD的原子模型与最近发表的与F-肌动蛋白结合的脊椎动物非肌肉肌球蛋白n的结构和无核苷酸肌球蛋白-V的晶体结构非常相似。与用兔骨骼肌肌球蛋白亚片段 1 装饰的 F-肌动蛋白的冷冻电镜结构相比，观察到更大的差异。这些差异表明肌动蛋白结合的骨骼肌肌球蛋白结构中 50 kDa 结构域的闭合程度较低。
Myosin-based motility utilizes catalysis of ATP to drive the relative sliding of F-actin and myosin. The earliest detailed model based on cryo-electron microscopy (cryoEM) and X-ray crystallography postulated that higher actin affinity and lever arm movement were coupled to closure of a feature of the myosin head dubbed the actin-binding cleft. Several studies since then using crystallography of myosin-V and cryoEM structures of F-actin bound myosin-I,-II and-V have provided details of this model. The smooth muscle myosin II interaction with F-actin may differ from those for striated and non-muscle myosin II due in part to different lengths of important surface loops. Here we report a similar to 6 A resolution reconstruction of F-actin decorated with the nucleotide-free recombinant smooth muscle myosin-II motor domain (MD) from images recorded using a direct electron detector. Resolution is highest for F-actin and the actin-myosin interface (3.5-4 A) and lowest (similar to 6-7 A) for those parts of the MD at the highest radius. Atomic models built into the F-actin density are quite comparable to those previously reported for rabbit muscle actin and show density from the bound ADP. The atomic model of the MD, is quite similar to a recently published structure of vertebrate non-muscle myosin n bound to F-actin and a crystal structure of nucleotide free myosin-V. Larger differences are observed when compared to the cryoEM structure of F-actin decorated with rabbit skeletal muscle myosin subfragment 1. The differences suggest less closure of the 50 kDa domain in the actin bound skeletal muscle myosin structure.