Conformational dynamics in substrate-binding domains influences transport in the ABC importer GlnPQ
Conformational dynamics in substrate-binding domains influences transport in the ABC importer GlnPQ
复制标题
DOI：
10.1038/nsmb.2929
复制
发表时间：
2015-01-01
影响因子：
16.8
通讯作者：
Poolman, Bert
中科院分区：
文献类型：
--
作者：
Gouridis, Giorgos;Schuurman-Wolters, Gea K.;Poolman, Bert
ABC转运蛋白的构象动力学在很大程度上是难以捉摸的。来自乳酸乳球菌的ABC进口商GlnPQ具有不同的共价连接的底物结合结构域（SBD），从而使其成为阐明SBD在运输中的动力学和作用的优良模型系统。我们通过单分子光谱证明，这两个SBD本质上从开放到封闭的无配体构象的转变，并且蛋白质通过诱导配合机制捕获它们的氨基酸配体。高亲和力的配体引起的转换，而不改变的封闭状态的寿命，而低亲和力的配体显着缩短it.We表明，SBD在封闭状态的竞争对接到转运，但值得注意的是，没有配体的效果是最强的。我们发现，速率决定步骤取决于SBD和氨基酸转运。我们得出结论，封闭构象的寿命控制SBD对接到转运蛋白和底物释放。
The conformational dynamics in ABC transporters is largely elusive. The ABC importer GlnPQ from Lactococcus lactis has different covalently linked substrate-binding domains (SBDs), thus making it an excellent model system to elucidate the dynamics and role of the SBDs in transport. We demonstrate by single-molecule spectroscopy that the two SBDs intrinsically transit from open to closed ligand-free conformation, and the proteins capture their amino acid ligands via an induced-fit mechanism. High-affinity ligands elicit transitions without changing the closed-state lifetime, whereas low-affinity ligands dramatically shorten it. We show that SBDs in the closed state compete for docking onto the translocator, but remarkably the effect is strongest without ligand. We find that the rate-determining steps depend on the SBD and the amino acid transported. We conclude that the lifetime of the closed conformation controls both SBD docking to the translocator and substrate release.