Reversible topological organization within a polytopic membrane protein is governed by a change in membrane phospholipid composition
Reversible topological organization within a polytopic membrane protein is governed by a change in membrane phospholipid composition
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DOI：
10.1074/jbc.m309840200
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发表时间：
2003-12-12
影响因子：
4.8
通讯作者：
Dowhan, W
中科院分区：
文献类型：
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作者：
Zhang, W;Bogdanov, M;Dowhan, W
一旦插入，多跨膜蛋白的跨膜区段通常被认为是稳定定向的，因为相邻膜外结构域的拓扑重定向存在较大的自由能垒。然而，大肠杆菌的多跨膜蛋白乳糖通透酶的拓扑结构和功能取决于膜磷脂组成，这揭示了在稳定插入膜后跨膜结构域的拓扑动力学（Bogdanov，M.，Heacock，P.N.和Dowhan，W.（2002年）《欧洲分子生物学组织杂志》21卷，2107 - 2116页）。在这项研究中，我们表明高亲和力苯丙氨酸通透酶PheP与乳糖通透酶有许多相似之处。在缺乏磷脂酰乙醇胺（PE）的大肠杆菌突变体中组装的PheP，与在含PE菌株中的PheP相比，其主动转运功能显著降低，并且N末端和相邻跨膜发夹环的拓扑定向完全反转。在PheP组装后引入PE会触发N末端和相邻发夹环重新定向到其天然定向，并恢复野生型转运功能。这些二级转运蛋白响应磷脂组成变化的可逆定向可能是转运功能所必需的固有构象灵活性的结果，或者是在蛋白质组装过程中产生的。
Once inserted, transmembrane segments of polytopic membrane proteins are generally considered stably oriented due to the large free energy barrier to topological reorientation of adjacent extramembrane domains. However, the topology and function of the polytopic membrane protein lactose permease of Escherichia coli are dependent on the membrane phospholipid composition, revealing topological dynamics of transmembrane domains after stable membrane insertion (Bogdanov, M., Heacock, P. N., and Dowhan, W. ( 2002) EMBO J. 21, 2107 - 2116). In this study, we show that the high affinity phenylalanine permease PheP shares many similarities with lactose permease. PheP assembled in a mutant of E. coli lacking phosphatidylethanolamine ( PE) exhibited significantly reduced active transport function and a complete inversion in topological orientation of the N terminus and adjoining transmembrane hairpin loop compared with PheP in a PE-containing strain. Introduction of PE following the assembly of PheP triggered a reorientation of the N terminus and adjacent hairpin to their native orientation associated with regain of wild-type transport function. The reversible orientation of these secondary transport proteins in response to a change in phospholipid composition might be a result of inherent conformational flexibility necessary for transport function or during protein assembly.