Elucidation of the transport mechanism of a secondary active transporter, Mhp1.

转运蛋白通过交替进入机制将底物转运穿过膜，其中蛋白质具有三种功能上不同的构象状态（面向外、封闭和面向内）。Mhp1是LeuT超家族的次级活性转运蛋白。我们成功地确定了Mhp1结构在这三个国家的交替访问机制。通过比较这些结构，发现这些状态之间的构象变化是通过四个螺旋相对于蛋白质其余部分的刚体运动来实现的。交替进入机制的分子基础在LeuT超家族中应该是共同的。

Transporters transport the substrates across the membrane by the alternating access mechanism in which the proteins have three functionally distinct conformational states(outward-facing, occluded, and inward-facing). Mhp1 is a secondary active transporter belonging to the LeuT superfamily. We succeeded to determine the Mhp1 structures in these three states of the alternating access mechanism. By the comparison of these structures, the conformational changes between these states are found to be achieved by the rigid body movement of the four helices relative to the rest of the protein. The molecular basis of the alternating access mechanism should be common among t he LeuT superfamily.