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分子机器，它旋转螺旋细丝，推动许多种类的游泳细菌。转子是细胞质膜中直径达45 nm的一组环3;定子包含约10个扭矩产生单元，其锚定在转子周边的细胞壁4，5。马达的自由能源是跨细胞质膜的离子的向内定向的电化学梯度，分别为H1驱动和Na 1驱动马达的质子动力或钠动力。在这里，我们展示了一个步进运动的钠驱动的嵌合体鞭毛电机在大肠杆菌6在低钠动力和控制表达少量的扭矩产生单位。我们观察到每转26步，这与FliG蛋白环的周期性一致，这是转子上扭矩产生的建议位点7，8。向后的步骤，尽管没有鞭毛开关蛋白CheY表明每一步的自由能的变化很小，类似于一个单一的离子过境。

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.