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

转运蛋白通过交替的通道机制将底物运输到膜上，在这种机制中，蛋白质有三种不同的功能构象状态(向外、封闭和向内)。Mhp1是Leut超家族的第二活性转运蛋白。我们成功地确定了交替通路机制这三种状态下的Mhp1结构。通过对这些结构的比较，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实现的。交替访问机制的分子基础在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.