Bonhivers M, Ghazi A, Boulanger P, Letellier L
Laboratoire des Biomembranes, URA CNRS 1116, Université Paris Sud, Orsay, France.
EMBO J. 1996 Apr 15;15(8):1850-6.
The Escherichia coli outer membrane protein FhuA catalyzes the transport of Fe3+(-)ferrichrome and is the receptor of phage T5 and phi 80. The purified protein inserted into planar lipid bilayers showed no channel activity. Binding of phage T5 and FhuA resulted in the appearance of high conductance ion channels. The electrophysiological characteristics of the channels (conductance, kinetic behavior, substates, ion selectivity including the effect of ferrichrome) showed similarities with those of the channel formed by a FhuA derivative from which the 'gating loop' (delta 322-355) had been removed. binding of phage T5 to FhuA in E.coli cells conferred SDS sensitivity to the bacteria, suggesting that such channels also exist in vivo. These data suggest that binding of T5 to loop 322-355 of FhuA, which constitutes the T5 binding site, unmasks an inner channel in FhuA. Both T5 and ferrichrome bind to the closed state of the channel but only T5 can trigger its opening.
大肠杆菌外膜蛋白FhuA催化Fe3+(-)高铁色素的转运，并且是噬菌体T5和φ80的受体。插入平面脂质双分子层的纯化蛋白未表现出通道活性。噬菌体T5与FhuA结合导致出现高电导离子通道。这些通道的电生理特性（电导、动力学行为、亚状态、离子选择性包括高铁色素的影响）与由去除了“门控环”（δ322 - 355）的FhuA衍生物形成的通道相似。噬菌体T5与大肠杆菌细胞中的FhuA结合使细菌对SDS敏感，这表明体内也存在此类通道。这些数据表明，T5与构成T5结合位点的FhuA的322 - 355环结合，使FhuA中的内部通道暴露。T5和高铁色素都与通道的关闭状态结合，但只有T5能触发其开放。
