Welch M, Oosawa K, Aizawa S, Eisenbach M
Department of Membrane Research and Biophysics, Weizmann Institute of Science, Rehovot, Israel.
Proc Natl Acad Sci U S A. 1993 Oct 1;90(19):8787-91. doi: 10.1073/pnas.90.19.8787.
Regulation of the direction of flagellar rotation is central to the mechanism of bacterial chemotaxis. The transitions between counterclockwise and clockwise rotation are controlled by a "switch complex" composed of three proteins (FliG, FliM, and FliN) and located at the base of the flagellar motor. The mechanism of function of the switch is unknown. Here we demonstrate that the diffusible clockwise-signal molecule, the CheY protein, binds to the switch, that the primary docking site is FliM, that the extent of CheY binding to FliM is dependent upon the phosphorylation level of CheY, and that it is unaffected by the other two switch proteins. This study provides a biochemical demonstration of binding of a signal molecule to the bacterial switch and demonstrates directly that phosphorylation regulates the activity of this molecule.
鞭毛旋转方向的调控是细菌趋化机制的核心。逆时针和顺时针旋转之间的转换由位于鞭毛马达基部的一种由三种蛋白质（FliG、FliM和FliN）组成的“开关复合体”控制。该开关的功能机制尚不清楚。在此我们证明，可扩散的顺时针信号分子CheY蛋白与该开关结合，主要对接位点是FliM，CheY与FliM的结合程度取决于CheY的磷酸化水平，且不受其他两种开关蛋白的影响。这项研究提供了信号分子与细菌开关结合的生化证据，并直接证明磷酸化调节该分子的活性。
