Direct observation of steps in rotation of the bacterial flagellar motor
Direct observation of steps in rotation of the bacterial flagellar motor
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DOI：
10.1038/nature04003
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发表时间：
2005-10-06
期刊：
影响因子：
64.8
通讯作者：
Berry, RM
中科院分区：
文献类型：
--
作者：
Sowa, Y;Rowe, AD;Berry, RM
细菌鞭毛马达是一种旋转的分子机器，它旋转推动许多种类游动细菌的螺旋细丝（1,2）。转子是细胞质膜上直径达45纳米的一组环(3)；定子包含大约10个扭矩发电单元，固定在转子周围的细胞壁上（4,5）。马达的自由能量来源是离子穿过细胞质膜的向内电化学梯度，即氢离子驱动和钠离子驱动马达的质子动力或钠离子动力。在这里，我们展示了大肠杆菌(6)中Na+驱动的嵌合鞭毛马达在低钠动力下的步进运动，并控制了少量扭矩产生单元的表达。我们观察到每转26步，这与flyg蛋白环的周期性一致，flyg蛋白是转子上产生扭矩的位置（7,8）。尽管没有鞭毛转换蛋白CheY，但后退一步表明每一步自由能的变化很小，类似于单个离子传递。
The bacterial flagellar motor is a rotary molecular machine that rotates the helical filaments that propel many species of swimming bacteria(1,2). The rotor is a set of rings up to 45 nm in diameter in the cytoplasmic membrane(3); the stator contains about ten torque-generating units anchored to the cell wall at the perimeter of the rotor(4,5). The free-energy source for the motor is an inward-directed electrochemical gradient of ions across the cytoplasmic membrane, the protonmotive force or sodium-motive force for H+-driven and Na+-driven motors, respectively. Here we demonstrate a stepping motion of a Na+-driven chimaeric flagellar motor in Escherichia coli(6) at low sodium-motive force and with controlled expression of a small number of torque-generating units. We observe 26 steps per revolution, which is consistent with the periodicity of the ring of FliG protein, the proposed site of torque generation on the rotor(7,8). Backwards steps despite the absence of the flagellar switching protein CheY indicate a small change in free energy per step, similar to that of a single ion transit.