Bogdanov Mikhail, Heacock Phillip N, Dowhan William
Department of Biochemistry and Molecular Biology, Medical School, University of Texas-Houston, Houston, TX 77225, USA.
EMBO J. 2002 May 1;21(9):2107-16. doi: 10.1093/emboj/21.9.2107.
To address the role of phospholipids in the topological organization of polytopic membrane proteins, the function and assembly of lactose permease (LacY) was studied in mutants of Escherichia coli lacking phosphatidylethanolamine (PE). PE is required for the proper conformation and active transport function of LacY. The N-terminal half of LacY assembled in PE-lacking cells adopts an inverted topology in which normally non-translocated domains are translocated and vice versa. Post-assembly synthesis of PE triggers a conformational change, resulting in a lipid-dependent recovery of normal conformation and topology of at least one LacY subdomain accompanied by restoration of active transport. These results demonstrate that membrane protein topology once attained can be changed in a reversible manner in response to alterations in phospholipid composition, and may be subject to post-assembly proofreading to correct misfolded structures.
为了研究磷脂在多跨膜蛋白拓扑组织中的作用，我们在缺乏磷脂酰乙醇胺（PE）的大肠杆菌突变体中研究了乳糖通透酶（LacY）的功能和组装。LacY的正确构象和主动运输功能需要PE。在缺乏PE的细胞中组装的LacY的N端一半采用了一种反向拓扑结构，其中通常不转运的结构域发生了转运，反之亦然。PE的组装后合成引发了构象变化，导致至少一个LacY亚结构域的正常构象和拓扑结构以脂质依赖的方式恢复，并伴随着主动运输的恢复。这些结果表明，一旦获得的膜蛋白拓扑结构可以响应磷脂组成的变化以可逆的方式改变，并且可能会在组装后进行校对以纠正错误折叠的结构。
