Clarification of the energy and signal transduction of bacterial flagellar motor using hybrid motor

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。转子是一组直径达45nm的环，位于细胞质膜中；定子包含大约10个扭矩发电单元，固定在转子四周的细胞壁上4,5。马达的自由能量来源是离子在细胞质膜上向内的电化学梯度，即h1驱动和na1驱动马达的质子动力或钠动力。在这里，我们展示了在低钠动力和少量扭矩产生单元的控制表达下，大肠杆菌6中由na1驱动的嵌合鞭毛马达的步进运动。我们观察到每转26步，这与FliG蛋白环的周期性一致，FliG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. The rotor is a set of rings up to 45nm in diameter in the cytoplasmic membrane3 ; the stator contains about ten torque generating units anchored to the cell wall at the perimeter of the rotor4, 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 H1-driven and Na1-driven motors, respectively. Here we demonstrate a stepping motion of a Na1-driven chimaeric flagellar motor in Escherichia coli6 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 rotor7, 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.