A molecular mechanism of direction switching in the flagellar motor of Escherichia coli
A molecular mechanism of direction switching in the flagellar motor of Escherichia coli
复制标题
DOI：
10.1073/pnas.1110111108
复制
发表时间：
2011-10-11
影响因子：
11.1
通讯作者：
Blair, David F.
中科院分区：
文献类型：
--
作者：
Paul, Koushik;Brunstetter, Duncan;Blair, David F.
鞭毛旋转的方向由安装在转子上的蛋白质组装体调节，称为“开关复合物”，由蛋白质FliG、FliM和FliN的多个拷贝形成。这些蛋白质的主要部分的结构是已知的，并且先前已经使用蛋白质结合、突变和交联方法的组合阐明了复合物中蛋白质的整体组织。在大肠杆菌中，从逆时针旋转到顺时针旋转的开关是由信号蛋白磷酸化CheY触发的，磷酸化CheY结合到开关复合物的下部，并诱导FliM和FliN亚基相对于彼此的微小运动。方向转换还必须在复合物的上部产生运动，特别是在FliG的C-末端结构域（FliG（C））中，其与定子相互作用以产生用于鞭毛旋转的扭矩。在本研究中，蛋白质运动的开关复合物的中间和上部已被探测通过有针对性的交联和突变分析。开关引起形成开关中间部分的FliM域的倾斜运动和随后的固定的FliGC域的旋转，其将定子相互作用位点重新定向约90度。在最近提出的运动机制假说中，FliGC的这种重新定向将逆转运动旋转的方向。
The direction of flagellar rotation is regulated by a rotor-mounted protein assembly, termed the "switch complex," formed from multiple copies of the proteins FliG, FliM, and FliN. The structures of major parts of these proteins are known, and the overall organization of proteins in the complex has been elucidated previously using a combination of protein-binding, mutational, and cross-linking approaches. In Escherichia coli, the switch from counter-clockwise to clockwise rotation is triggered by the signaling protein phospho-CheY, which binds to the lower part of the switch complex and induces small movements of FliM and FliN subunits relative to each other. Direction switching also must produce movements in the upper part of the complex, particularly in the C-terminal domain of FliG (FliG(C)), which interacts with the stator to generate the torque for flagellar rotation. In the present study, protein movements in the middle and upper parts of the switch complex have been probed by means of targeted cross-linking and mutational analysis. Switching induces a tilting movement of the FliM domains that form the middle part of the switch and a consequent rotation of the affixed FliGC domains that reorients the stator interaction sites by about 90 degrees. In a recently proposed hypothesis for the motor mechanism, such a reorientation of FliGC would reverse the direction of motor rotation.