Serohijos Adrian W R, Chen Yiwen, Ding Feng, Elston Timothy C, Dokholyan Nikolay V
Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599, USA.
Proc Natl Acad Sci U S A. 2006 Dec 5;103(49):18540-5. doi: 10.1073/pnas.0602867103. Epub 2006 Nov 22.
Intracellular active transport is driven by ATP-hydrolyzing motor proteins that move along cytoskeletal filaments. In particular, the microtubule-associated dynein motor is involved in the transport of organelles and vesicles, the maintenance of the Golgi, and mitosis. However, unlike kinesin and myosin, the mechanism by which dynein converts chemical energy into mechanical force remains largely a mystery, due primarily to the lack of a high-resolution molecular structure. Using homology modeling and normal mode analysis, we propose a complete atomic structure and a mechanism for force generation by the motor protein dynein. In agreement with very recent electron microscopy (EM) reconstructions showing dynein as a ring-shaped heptamer, our model consists of six ATPases of the AAA (ATPases associated with various cellular activities) superfamily and a C-terminal domain, which is experimentally known to control motor function. Our model shows a coiled coil spanning the diameter of the motor that accounts for previously unidentified structures in EM studies and provides a potential mechanism for long-range communication between the AAA domains. Furthermore, normal mode analysis reveals that the subunits of the motor that contain the nucleotide binding sites exhibit minimal movement, whereas the rest of the motor is very mobile. Our analysis suggests the likely domain rearrangements of the motor unit that generate its power stroke. This study provides insights into the structure and function of dynein that can guide further experimental investigations into energy transduction in dynein.
细胞内的主动运输由沿着细胞骨架细丝移动的ATP水解驱动蛋白所推动。特别地，与微管相关的动力蛋白参与细胞器和囊泡的运输、高尔基体的维持以及有丝分裂。然而，与驱动蛋白和肌球蛋白不同，动力蛋白将化学能转化为机械力的机制在很大程度上仍是个谜，这主要是由于缺乏高分辨率的分子结构。通过同源建模和正常模式分析，我们提出了动力蛋白驱动蛋白的完整原子结构和力产生机制。与最近的电子显微镜（EM）重建结果一致，该结果显示动力蛋白为环形七聚体，我们的模型由AAA（与各种细胞活动相关的ATP酶）超家族的六个ATP酶和一个C端结构域组成，实验已知该结构域可控制运动功能。我们的模型显示了一个横跨动力蛋白直径的卷曲螺旋，这解释了EM研究中先前未识别的结构，并为AAA结构域之间的远程通信提供了一种潜在机制。此外，正常模式分析表明，包含核苷酸结合位点的动力蛋白亚基运动极小，而动力蛋白的其余部分则非常活跃。我们的分析表明了动力蛋白单元可能产生其动力冲程的结构域重排。这项研究为动力蛋白的结构和功能提供了见解，可指导对动力蛋白能量转导的进一步实验研究。
