Effect of Intracellular pH on the Torque-Speed Relationship of Bacterial Proton-Driven Flagellar Motor
Effect of Intracellular pH on the Torque-Speed Relationship of Bacterial Proton-Driven Flagellar Motor
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DOI：
10.1016/j.jmb.2008.12.034
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发表时间：
2009-02-20
影响因子：
5.6
通讯作者：
Namba, Keiichi
中科院分区：
文献类型：
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作者：
Nakamura, Shuichi;Kami-ike, Nobunori;Namba, Keiichi
负责运动的细菌鞭毛由旋转电机驱动，该电机由跨细胞质膜的特定离子的电化学势差提供动力。质子驱动鞭毛电机的定子将质子流入转化为机械功。然而，能量转换机制仍不清楚。在这里，我们表明，电机在低负载下高速旋转时对细胞内质子浓度敏感，降低细胞内 pH 值会严重损害这种浓度，而零速扭矩则不受影响。细胞外pH值的变化没有显示出任何影响。这些结果表明，高细胞内质子浓度会降低质子易位的速率，从而降低电机的机械化学反应循环的速率，但不会降低循环中定子-转子相互作用产生的实际扭矩步骤。 (C) 2008 Elsevier Ltd. 保留所有权利。
Bacterial flagella responsible for motility are driven by rotary motors powered by the electrochemical potential difference of specific ions across the cytoplasmic membrane. The stator of proton-driven flagellar motor converts proton influx into mechanical work. However, the energy conversion mechanism remains unclear. Here, we show that the motor is sensitive to intracellular proton concentration for high-speed rotation at low load, which was considerably impaired by lowering intracellular pH, while zero-speed torque was not affected. The change in extracellular pH did not show any effect. These results suggest that a high intracellular proton concentration decreases the rate of proton translocation and therefore that of the mechanochemical reaction cycle of the motor but not the actual torque generation step within the cycle by the stator-rotor interactions. (C) 2008 Elsevier Ltd. All rights reserved.