Zhou J, Lloyd S A, Blair D F
Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
Proc Natl Acad Sci U S A. 1998 May 26;95(11):6436-41. doi: 10.1073/pnas.95.11.6436.
Bacterial flagellar motors rotate, obtaining power from the membrane gradient of protons or, in some species, sodium ions. Torque generation in the flagellar motor must involve interactions between components of the rotor and components of the stator. Sites of interaction between the rotor and stator have not been identified. Mutational studies of the rotor protein FliG and the stator protein MotA showed that both proteins contain charged residues essential for motor rotation. This suggests that functionally important electrostatic interactions might occur between the rotor and stator. To test this proposal, we examined double mutants with charged-residue substitutions in both the rotor protein FliG and the stator protein MotA. Several combinations of FliG mutations with MotA mutations exhibited strong synergism, whereas others showed strong suppression, in a pattern that indicates that the functionally important charged residues of FliG interact with those of MotA. These results identify a functionally important site of interaction between the rotor and stator and suggest a hypothesis for electrostatic interactions at the rotor-stator interface.
细菌鞭毛马达旋转，从质子的膜梯度中获取能量，在某些物种中则从钠离子的膜梯度中获取能量。鞭毛马达中扭矩的产生必定涉及转子组件和定子组件之间的相互作用。转子和定子之间的相互作用位点尚未确定。对转子蛋白FliG和定子蛋白MotA的突变研究表明，这两种蛋白都含有对马达旋转至关重要的带电荷残基。这表明转子和定子之间可能发生功能上重要的静电相互作用。为了验证这一假设，我们研究了在转子蛋白FliG和定子蛋白MotA中都带有电荷残基替代的双突变体。FliG突变与MotA突变的几种组合表现出强烈的协同作用，而其他组合则表现出强烈的抑制作用，其模式表明FliG的功能上重要的带电荷残基与MotA的带电荷残基相互作用。这些结果确定了转子和定子之间功能上重要的相互作用位点，并提出了转子-定子界面静电相互作用的假设。
