施一公2014-04-14 4:57 PM

细菌细胞外液转运因子的S组成成分的结构和机制 Structure and mechanism of the S component of a bacterial ECF transporter.

论文摘要
在原核生物中负责维生素摄取的能量耦合因子(ECF)转运蛋白是膜转运蛋白中的独特类别。每个ECF转运蛋白包含了膜嵌入底物结合蛋白(即S成分),即能量耦合模块包括两种ATP结合蛋白(即A和A'成分)和一种跨膜蛋白(即T成分)。但我们对ECF类别的结构和传输机制仍所知甚少。在此我们展示了RibU的晶体结构以及3.6 - Å分辨率下金黄色葡萄球菌ECF类别核黄素转运蛋白的S成分。RibU包含六个跨膜片段,采用了前所未有的转运蛋白折叠并含有与L1循环和4-6跨膜段周质部分结合的核黄素分子。结构分析表明必要的配体结合残基确定了推定的传送路径,并利用序列比对揭示了保守性结构特点且建议了ECF转运蛋白中的潜在活动机制。
Abstract
The energy-coupling factor (ECF) transporters, responsible for vitamin uptake in prokaryotes, are a unique family of membrane transporters. Each ECF transporter contains a membrane-embedded, substrate-binding protein (known as the S component), an energy-coupling module that comprises two ATP-binding proteins (known as the A and A' components) and a transmembrane protein (known as the T component). The structure and transport mechanism of the ECF family remain unknown. Here we report the crystal structure of RibU, the S component of the ECF-type riboflavin transporter from Staphylococcus aureus at 3.6-Å resolution. RibU contains six transmembrane segments, adopts a previously unreported transporter fold and contains a riboflavin molecule bound to the L1 loop and the periplasmic portion of transmembrane segments 4-6. Structural analysis reveals the essential ligand-binding residues, identifies the putative transport path and, with sequence alignment, uncovers conserved structural features and suggests potential mechanisms of action among the ECF transporters.

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