Le Dain A C, Häse C C, Tommassen J, Martinac B
Department of Pharmacology, University of Western Australia, Nedlands, WA, Australia.
EMBO J. 1996 Jul 15;15(14):3524-8.
OmpC and PhoE porins of Escherichia coli were examined by the patch-clamp technique following reconstitution in liposomes, and were observed primarily in the open (conducting) state. With application of negative voltage and positive hydrostatic pressure, OmpC exhibited marked gating towards a more closed state whereas PhoE remained largely unaffected by pressure application. Hybrid chimeric OmpC-PhoE proteins showed an increased tendency for pressure-dependent gating as the OmpC proportion in the chimeric molecule increased. In addition, several PhoE mutants with amino acid substitutions and insertions in either the L3 or L4 loop of the monomer exhibited pressure sensitivity comparable with the wild-type OmpC porin. Our data support the structural plasticity model of porins and are consistent with the 'charge-screening-unscreening' hypothesis that describes how these proteins may exist in distinct conformations.
利用膜片钳技术对脂质体重构后的大肠杆菌OmpC和PhoE孔蛋白进行了检测，发现它们主要处于开放（导电）状态。施加负电压和正静水压力后，OmpC表现出明显的向更关闭状态的门控特性，而PhoE在施加压力时基本不受影响。随着嵌合分子中OmpC比例的增加，杂合嵌合OmpC-PhoE蛋白表现出对压力依赖性门控的增强趋势。此外，在单体的L3或L4环中具有氨基酸取代和插入的几个PhoE突变体表现出与野生型OmpC孔蛋白相当的压力敏感性。我们的数据支持孔蛋白的结构可塑性模型，并且与描述这些蛋白质如何以不同构象存在的“电荷筛选-去筛选”假说一致。
