Salt-bridge dynamics control substrate-induced conformational change in the membrane transporter GlpT
Salt-bridge dynamics control substrate-induced conformational change in the membrane transporter GlpT
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DOI：
10.1016/j.jmb.2008.03.029
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发表时间：
2008-05-09
影响因子：
5.6
通讯作者：
Wang, Da-Neng
中科院分区：
文献类型：
--
作者：
Law, Christopher J.;Almqvist, Jonas;Wang, Da-Neng
底物跨细胞质膜的主动转运具有重要的生理、医学和药学重要性。大肠杆菌内膜的 3-磷酸甘油 (G3P) 转运蛋白 (GlpT) 是来自普遍存在的主要促进子超家族的次级活性逆向转运蛋白，它耦合 G3P 的输入？无机磷酸盐 (Pi) 沿着其浓度梯度流出。整合来自结构、分子动力学模拟和生化研究的新组合的信息，我们确定了直接参与底物与 GlpT 内向构象结合的残基，从而定义了该转运蛋白的底物特异性的结构基础。底物结合机制涉及结合位点组氨酸残基的质子化。此外，我们的数据表明，域间和域内盐桥的形成和破坏控制着伴随底物跨膜易位的转运蛋白的构象变化。我们提出的机制可能是有机磷酸盐：磷酸盐逆向转运蛋白的范例。 (c) 2008 Elsevier Ltd. 保留所有权利。
Active transport of substrates across cytoplasmic membranes is of great physiological, medical and pharmaceutical importance. The glycerol-3-phosphate (G3P) transporter (GlpT) of the E. coli inner membrane is a secondary active antiporter from the ubiquitous major facilitator superfamily that couples the import of G3P? to the efflux of inorganic phosphate (Pi) down its concentration gradient. Integrating information from a novel combination of structural, molecular dynamics simulations and biochemical studies, we identify the residues involved directly in binding of substrate to the inward-facing conformation of GlpT, thus defining the structural basis for the substrate-specificity of this transporter. The substrate binding mechanism involves protonation of a histidine residue at the binding site. Furthermore, our data suggest that the formation and breaking of inter- and intradomain salt bridges control the conformational change of the transporter that accompanies substrate translocation across the membrane. The mechanism we propose may be a paradigm for organophosphate:phosphate antiporters. (c) 2008 Elsevier Ltd. All rights reserved.