Miller S, Douglas R M, Carter P, Booth I R
Department of Molecular and Cell Biology, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom.
J Biol Chem. 1997 Oct 3;272(40):24942-7. doi: 10.1074/jbc.272.40.24942.
The kefC gene of Escherichia coli encodes a potassium efflux system that is gated by glutathione (GSH) and by GSH adducts. Independently isolated kefC mutations that result in spontaneous activation of the efflux system have been analyzed. Three mutations affect residues located adjacent to the conserved Rossman fold in the carboxyl-terminal domain. Two mutations lie in a sequence predicted to form a cytoplasmically located loop in the membrane domain of KefC. All of the mutants retain normal regulation by the YabF protein and by GSH adducts. A mutation in the Rossman fold, R416S, alters the normal regulation of KefC by GSH. In contrast to the wild-type protein, which is inactive in the presence of GSH, the R416S mutant is only active in the presence of GSH or its analogue, ophthalmic acid. Other mutations in this region or elsewhere in the protein have their spontaneous activity augmented by depletion of the GSH pool. These data identify a specific role for the carboxyl-terminal domain of KefC in regulating KefC activity and are discussed in the light of recent data that suggest that GSH adducts can bind within a Rossman fold.
大肠杆菌的kefC基因编码一种钾离子外流系统，该系统由谷胱甘肽（GSH）及其加合物控制。对独立分离出的导致外流系统自发激活的kefC突变进行了分析。三个突变影响位于羧基末端结构域中与保守的罗斯曼折叠相邻的残基。两个突变位于预测在KefC膜结构域中形成胞质环的序列中。所有突变体通过YabF蛋白和GSH加合物保持正常调控。罗斯曼折叠中的R416S突变改变了GSH对KefC的正常调控。与在GSH存在下无活性的野生型蛋白不同，R416S突变体仅在GSH或其类似物眼酸存在下有活性。该区域或蛋白其他位置的其他突变通过GSH池的消耗增强其自发活性。这些数据确定了KefC羧基末端结构域在调节KefC活性中的特定作用，并根据最近表明GSH加合物可结合在罗斯曼折叠内的数据进行了讨论。
