Welch M, Margolin Y, Caplan S R, Eisenbach M
Department of Membrane Research and Biophysics, Weizmann Institute of Science, Rehovot, Israel.
Biochim Biophys Acta. 1995 Jul 20;1268(1):81-7. doi: 10.1016/0167-4889(95)00054-v.
The flagellar motor of Escherichia coli (E. coli) is driven by a proton-motive force (PMF), hence it was of interest to determine whether the motor is symmetrical in the sense that it can be rotated by any polarity of PMF. For this purpose the cells had to be deenergized first. Conventional deenergization procedures caused irreversible loss of motility, presumably due to ATP-dependent degradative processes. However, E. coli cells deenergized by incubation with arsenate manifested a slow, reversible depletion of PMF. In this procedure there was a sufficiently long time window, during which a considerable proportion of the cells lost their motility and could be made to rotate again by an artificially-imposed PMF. The motors of these cells rotated in response to any PMF polarity, but positive and negative polarities rotated different sub-populations of cells and the direction was almost exclusively counterclockwise. The reason for the unidirectionality of the rotation was not the intervention of the chemotaxis system. A number of potential reasons are suggested. One is the arsenate effect on the motor function found previously [Margolin, Y., Barak, R. and Eisenbach, M. (1994) J. Bacteriol. 176, 5547-5549]. A possible interaction between arsenate and the motor is discussed.
大肠杆菌（E. coli）的鞭毛马达由质子动力（PMF）驱动，因此确定该马达在可被任何极性的PMF驱动旋转这一意义上是否对称是很有意义的。为此，必须先使细胞去能。传统的去能程序会导致不可逆的运动性丧失，推测这是由于ATP依赖的降解过程。然而，用砷酸盐孵育去能的大肠杆菌细胞表现出PMF的缓慢、可逆消耗。在这个过程中有一个足够长的时间窗口，在此期间相当一部分细胞失去了运动性，并且可以通过人为施加的PMF再次使其旋转。这些细胞的马达对任何PMF极性都有反应，但正极性和负极性驱动不同亚群的细胞旋转，并且方向几乎完全是逆时针的。旋转单向性的原因不是趋化系统的干预。文中提出了一些潜在原因。其中之一是先前发现的砷酸盐对马达功能的影响[Margolin, Y., Barak, R. and Eisenbach, M. (1994) J. Bacteriol. 176, 5547 - 5549]。文中还讨论了砷酸盐与马达之间可能的相互作用。
