Iwazawa J, Imae Y, Kobayasi S
Department of Molecular Biology, School of Science, Nagoya University, Japan.
Biophys J. 1993 Mar;64(3):925-33. doi: 10.1016/S0006-3495(93)81454-1.
Bacterial flagella are driven by a rotary motor that is energized by an electrochemical ion gradient across the cell membrane. In this study the torque generated by the flagellar motor was measured in tethered cells of a smooth-swimming Escherichia coli strain by using rotating electric fields to determine the relationship between the torque and speed over a wide range. By measuring the electric current applied to the sample cell and combining the data obtained at different viscosities, the torque of the flagellar motor was estimated up to 55 Hz, and also at negative rotation rates. By this method we have found that the torque of the flagellar motor linearly decreases with rotation rate from negative through positive rate of rotation. In addition, the dependence of torque upon temperature was also investigated. We showed that torque at the high speeds encountered in swimming cells had a much steeper dependence on temperature that at the low speeds encountered in tethered cells. From these results, the activation energy of the proton transfer reaction in the torque-generating unit was calculated to be about 7.0 x 10(-20) J.
细菌鞭毛由一个旋转马达驱动，该马达由跨细胞膜的电化学离子梯度提供能量。在本研究中，通过使用旋转电场在一株游动平稳的大肠杆菌的系留细胞中测量鞭毛马达产生的扭矩，以确定在很宽范围内扭矩与速度之间的关系。通过测量施加到样品池的电流并结合在不同粘度下获得的数据，估计了鞭毛马达在高达55赫兹时以及在负旋转速率下的扭矩。通过这种方法我们发现，鞭毛马达的扭矩随着旋转速率从负到正线性下降。此外，还研究了扭矩对温度的依赖性。我们表明，在游动细胞中遇到的高速下的扭矩对温度的依赖性比在系留细胞中遇到的低速下的扭矩对温度的依赖性陡峭得多。根据这些结果，计算出扭矩产生单元中质子转移反应的活化能约为7.0×10⁻²⁰焦耳。
