National Laboratory of Macromolecules, National Center of Protein Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
Proc Natl Acad Sci U S A. 2013 Sep 3;110(36):14664-9. doi: 10.1073/pnas.1308127110. Epub 2013 Aug 15.
The major facilitator superfamily (MFS) is the largest family of secondary active transporters and is present in all life kingdoms. Detailed structural basis of the substrate transport and energy-coupling mechanisms of these proteins remain to be elucidated. YajR is a putative proton-driven MFS transporter found in many Gram-negative bacteria. Here we report the crystal structure of Escherichia coli YajR at 3.15 Å resolution in an outward-facing conformation. In addition to having the 12 canonical transmembrane helices, the YajR structure includes a unique 65-residue C-terminal domain which is independently stable. The structure is unique in illustrating the functional role of "sequence motif A." This highly conserved element is seen to stabilize the outward conformation of YajR and suggests a general mechanism for the conformational change between the inward and outward states of the MFS transporters.
主要易化超家族（MFS）是次级主动转运蛋白中最大的家族，存在于所有生命王国中。这些蛋白质的底物转运和能量偶联机制的详细结构基础仍有待阐明。YajR 是一种假定的质子驱动 MFS 转运蛋白，存在于许多革兰氏阴性菌中。在这里，我们报道了大肠杆菌 YajR 在向外开放构象下的 3.15Å 分辨率的晶体结构。除了具有 12 个典型的跨膜螺旋外，YajR 结构还包括一个独特的 65 个残基的 C 末端结构域，该结构域是独立稳定的。该结构独特之处在于说明了“序列基序 A”的功能作用。这个高度保守的元件被认为稳定了 YajR 的外向构象，并为 MFS 转运蛋白的内向和外向状态之间的构象变化提供了一个通用机制。
