菌鞭毛細(xì)絲的轉(zhuǎn)動(dòng)是細(xì)菌運(yùn)動(dòng)的原因,。轉(zhuǎn)動(dòng)的方向決定細(xì)菌是會(huì)平穩(wěn)向前運(yùn)動(dòng)還是會(huì)改變其運(yùn)動(dòng)軌跡。鞭毛“馬達(dá)”向順時(shí)針方向或逆時(shí)針方向驅(qū)動(dòng)這種轉(zhuǎn)動(dòng),，轉(zhuǎn)動(dòng)方向由鞭毛開關(guān)復(fù)合物調(diào)控,。
它的組成部分之一（一種被稱為FliG的環(huán)狀蛋白）施加使該“馬達(dá)”能夠切換方向的扭動(dòng)運(yùn)動(dòng)或扭矩——這是一個(gè)引人注目的本領(lǐng)，因?yàn)楸廾悦棵霂装俎D(zhuǎn)的速度轉(zhuǎn)動(dòng),，但能夠在不到一毫秒時(shí)間內(nèi)逆轉(zhuǎn)方向?，F(xiàn)在，F(xiàn)IiG的全長(zhǎng)度結(jié)構(gòu)已被確定,，在轉(zhuǎn)動(dòng)方向的切換中所涉及的構(gòu)形變化也被識(shí)別了出來(lái),。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature doi:10.1038/nature09300
Structure of the torque ring of the flagellar motor and the molecular basis for rotational switching
Lawrence K. Lee,Michael A. Ginsburg,Claudia Crovace,Mhairi Donohoe& Daniela Stock
The flagellar motor drives the rotation of flagellar filaments at hundreds of revolutions per second1, 2, efficiently propelling bacteria through viscous media3. The motor uses the potential energy from an electrochemical gradient of cations4, 5 across the cytoplasmic membrane to generate torque. A rapid switch from anticlockwise to clockwise rotation determines whether a bacterium runs smoothly forward or tumbles to change its trajectory6, 7. A protein called FliG forms a ring in the rotor of the flagellar motor that is involved in the generation of torque8, 9, 10, 11, 12, 13 through an interaction with the cation-channel-forming stator subunit MotA12. FliG has been suggested to adopt distinct conformations that induce switching but these structural changes and the molecular mechanism of switching are unknown. Here we report the molecular structure of the full-length FliG protein, identify conformational changes that are involved in rotational switching and uncover the structural basis for the formation of the FliG torque ring. This allows us to propose a model of the complete ring and switching mechanism in which conformational changes in FliG reverse the electrostatic charges involved in torque generation.
