一种核黄素(维生素 B2)膜运输因子（重要能量耦合因子(ECF)家族的一个成员）的X-射线晶体结构已被确定。来自金黄葡萄球菌的运输因子的“膜嵌入基质结合域”的结构显示了一个以前没有报道过的折叠，其中核黄素分子结合在一个环及几个跨膜片段的周质部分上。（生物谷Bioon.com）
生物谷推荐原文出处：
Nature doi:10.1038/nature09488
Structure and mechanism of the S component of a bacterial ECF transporter
Peng Zhang1, Jiawei Wang2 & Yigong Shi3
1.Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Princeton, New Jersey 08544, USA
2.State Key Laboratory of Biomembrane and Membrane Biotechnology, Center for Structural Biology, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China
3.Ministry of Education Protein Science Laboratory, Center for Structural Biology, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China
Top of pageAbstractThe energy-coupling factor (ECF) transporters, responsible for vitamin uptake in prokaryotes, are a unique family of membrane transporters1, 2. 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-? 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.
