The glycerol-3-phosphate transporter (GlpT) is a member of the major facilitator superfamily (MFS). GlpT is an organic phosphate/inorganic phosphate antiporter. It shares a similar fold with other MFS transporters (e.g. LacY and EmrD) consisting of 12 transmembrane (TM) helices which form two domains (each of six TM helices) surrounding a central ligand-binding cavity. The TM helices (especially the cavity-lining helices) contain a large number of proline and glycine residues, which may aid in the conformational changes believed to underline the transport mechanism. Molecular dynamics simulations in a phospholipid bilayer have been used to compare the conformational properties of the isolated TM helices with those in the intact GlpT protein. Analysis of these simulations focuses on the role of proline-induced flexibility in the TM helices. Our results are consistent with the proposed rocker switch mechanism for transport by GlpT. In particular, the simulations highlight the cavity-lining helices (H4, H5, H10 and H11) as being significantly flexible, suggesting that the transport mechanism may involve intra-helix motions in addition to pseudo-rigid body motions of the N- and C-terminal domains relative to one another.

中文翻译：

---

膜转运蛋白中的螺旋动力学：甘油3-磷酸转运蛋白及其组成螺旋的比较模拟。

甘油3-磷酸转运蛋白（GlpT）是主要促进子超家族（MFS）的成员。GlpT是有机磷酸盐/无机磷酸盐反向转运蛋白。它与其他由12个跨膜（TM）螺旋组成的MFS转运蛋白（例如LacY和EmrD）具有相似的折叠，形成围绕着中心配体结合腔的两个域（六个TM螺旋中的每一个）。TM螺旋（特别是腔衬螺旋）含有大量脯氨酸和甘氨酸残基，这可能有助于构象变化，从而强调了转运机制。磷脂双层中的分子动力学模拟已用于比较分离的TM螺旋和完整GlpT蛋白中的螺旋构象。这些模拟的分析重点在于脯氨酸诱导的弹性在TM螺旋中的作用。我们的结果与提出的用于GlpT运输的翘板开关机制是一致的。尤其是，模拟突出显示了腔衬螺旋（H4，H5，H10和H11）具有显着的柔韧性，这表明除了N和C的拟刚性身体运动外，转运机制还可能涉及螺旋内运动-末端域相对于彼此。