Structures of FolT in substrate-bound and substrate-released conformations reveal a gating mechanism for ECF transporters.
Structures of FolT in substrate-bound and substrate-released conformations reveal a gating mechanism for ECF transporters.
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FolT 底物结合和释放构象的结构揭示了 ECF 转运蛋白的门控机制
DOI：
10.1038/ncomms8661
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发表时间：
2015-07-22
影响因子：
16.6
通讯作者：
Zhang P
中科院分区：
文献类型：
--
作者：
Zhao Q;Wang C;Wang C;Guo H;Bao Z;Zhang M;Zhang P
能量偶联因子转运蛋白（ECF）是ABC转运蛋白的一个新家族，由四个亚基组成：两个胞质ATP酶EcfA和EcfA'，两个跨膜蛋白EcfS和EcfT。在这里，我们报告的3.2-kDa分辨率的晶体结构的叶酸ECF转运蛋白从粪肠球菌EfFolT，一个密切的同源物的FolT从短乳杆菌LbFolT。结构和生化分析揭示了构成叶酸结合口袋的残基，并确定底物结合特异性。叶酸结合的EfFolT与不含叶酸的LbFolT的全息转运蛋白复合物的结构比较揭示了L1环的显著构象变化，并揭示了ECF转运蛋白的门控机制，其中EcfS的L1环在底物结合和释放中充当门控。 ECF转运蛋白的底物特异性由跨膜EcfS蛋白亚基决定。Zhao等人在本文中介绍了细菌叶酸转运蛋白EcfS的底物结合和底物释放结构，并提出了ECF转运蛋白的门控机制。
Energy-coupling factor (ECF) transporters are a new family of ABC transporters that consist of four subunits, two cytoplasmic ATPases EcfA and EcfA' and two transmembrane proteins namely EcfS for substrate-specific binding and EcfT for energy coupling. Here, we report the 3.2-Å resolution crystal structure of the EcfS protein of a folate ECF transporter from Enterococcus faecalis-EfFolT, a close homologue of FolT from Lactobacillus brevis-LbFolT. Structural and biochemical analyses reveal the residues constituting the folate-binding pocket and determining the substrate-binding specificity. Structural comparison of the folate-bound EfFolT with the folate-free LbFolT contained in the holotransporter complex discloses significant conformational change at the L1 loop, and reveals a gating mechanism of ECF transporters in which the L1 loop of EcfS acts as a gate in the substrate binding and release. Substrate specificity of ECF transporters is determined by the transmembrane EcfS protein subunit. Here Zhao et al. present substrate-bound and substrate-released structures of a bacterial folate transporter EcfS and suggest a gating mechanism for ECF transporters.