The prototypical H+/galactose symporter GalP assembles into functional trimers.
The prototypical H+/galactose symporter GalP assembles into functional trimers.
复制标题
原型 H /半乳糖同向转运蛋白 GalP 组装成功能性三聚体。
DOI：
10.1016/j.jmb.2009.12.010
复制
发表时间：
2010
影响因子：
5.6
通讯作者：
Gonen,Tamir
中科院分区：
文献类型：
--
作者：
Zheng,Hongjin;Taraska,Justin;Merz,AlexeyJ;Gonen,Tamir
葡萄糖是人体细胞的主要能量来源。葡萄糖转运体形成专门的膜通道，用于糖进出细胞的运输。半乳糖渗透酶（GalP）是最接近人类促进葡萄糖转运蛋白的细菌同源物。在这里，我们报道了GalP的功能重构和二维结晶。纯化GalP的单粒子电子显微镜分析表明，该蛋白以三种不同密度的低聚物组装。重构分析产生二维GalP晶体，显示出具有p3对称的六边形阵列。GalP在18 Å分辨率下的投影结构表明该蛋白为三聚体。三聚体中的每个单体形成自己的通道，但在低聚物的3倍轴上明显存在额外的空腔（直径10 ~ 15 Å）。我们发现晶体GalP能够选择性地结合底物，这表明三聚体形式具有生物活性。
Glucose is a primary source of energy for human cells. Glucose transporters form specialized membrane channels for the transport of sugars into and out of cells. Galactose permease (GalP) is the closest bacterial homolog of human facilitated glucose transporters. Here, we report the functional reconstitution and 2D crystallization of GalP. Single particle electron microscopy analysis of purified GalP shows that the protein assembles as an oligomer with three distinct densities. Reconstitution assays yield 2D GalP crystals that exhibit a hexagonal array having p3 symmetry. The projection structure of GalP at 18 Å resolution shows that the protein is trimeric. Each monomer in the trimer forms its own channel, but an additional cavity (10∼15 Å in diameter) is apparent at the 3-fold axis of the oligomer. We show that the crystalline GalP is able to selectively bind substrate, suggesting that the trimeric form is biologically active.