Three-Dimensional Microscopy Research Team, RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan.
J Mol Biol. 2010 Mar 19;397(1):179-89. doi: 10.1016/j.jmb.2010.01.027. Epub 2010 Jan 25.
The membrane domain of human erythrocyte anion exchanger 1 (AE1) works as a Cl(-)/HCO(3)(-) antiporter. This exchange is a key step for CO(2)/O(2) circulation in the blood. In spite of their importance, structural information about AE1 and the AE (anion exchanger) family are still very limited. We used electron microscopy to solve the three-dimensional structure of the AE1 membrane domain, fixed in an outward-open conformation by cross-linking, at 7.5-A resolution. A dimer of AE1 membrane domains packed in two-dimensional array showed a projection map similar to that of the prokaryotic homolog of the ClC chloride channel, a Cl(-)/H(+) antiporter. In a three-dimensional map, there are V-shaped densities near the center of the dimer and slightly narrower V-shaped clusters at a greater distance from the center of the dimer. These appear to be inserted into the membrane from opposite sides. The structural motifs, two homologous pairs of helices in internal repeats of the ClC transporter (helices B+C and J+K), are well fitted to those AE1 densities after simple domain movement.
人红细胞阴离子交换器 1（AE1）的膜结构域作为 Cl(-)/HCO(3)(-)反向转运体起作用。这种交换是血液中 CO(2)/O(2)循环的关键步骤。尽管它们很重要，但 AE1 和 AE（阴离子交换器）家族的结构信息仍然非常有限。我们使用电子显微镜以 7.5-A 分辨率解决了通过交联固定在向外开放构象中的 AE1 膜结构域的三维结构。二维排列的 AE1 膜结构域二聚体显示出类似于 ClC 氯离子通道（Cl(-)/H(+)反向转运体）的原核同源物的投影图。在三维图谱中，二聚体中心附近有 V 形密度，而距离二聚体中心稍远的地方则有较窄的 V 形簇。这些似乎从相对的两侧插入膜中。结构基序，ClC 转运蛋白内部重复的两对同源螺旋（螺旋 B+C 和 J+K），在简单的结构域运动后很好地适合于那些 AE1 密度。
