Department of Biochemistry and Molecular Biophysics Washington University School of Medicine, St. Louis, MO 63110, United States.
Curr Opin Struct Biol. 2012 Feb;22(1):38-43. doi: 10.1016/j.sbi.2011.10.004. Epub 2011 Nov 16.
The small multidrug resistance transporters represent a unique model system for studying the mechanism of secondary active transport and membrane protein evolution. However, this seemingly simple protein has been highly controversial. Recent studies have provided experimental evidence that EmrE exists as an asymmetric dimer that exchanges between identical inward-facing and outward-facing states. Re-examination of the published literature in light of these findings fills in many details of the microscopic steps in the transport cycle. Future work will need to examine how the symmetry observed in vitro affects EmrE function in the asymmetric environment of its native Escherichia coli membrane.
小多重耐药转运蛋白是研究次级主动转运和膜蛋白进化机制的独特模型系统。然而，这种看似简单的蛋白质却极具争议。最近的研究提供了实验证据，表明 EmrE 以不对称二聚体的形式存在，在相同的内向和外向构象之间交换。根据这些发现重新审视已发表的文献，填补了转运循环中微观步骤的许多细节。未来的工作需要研究在体外观察到的对称性如何影响 EmrE 在其天然大肠杆菌膜的不对称环境中的功能。
