Crystal structure of human Band3 (anion exchanger)

阴离子交换基因（AE）家族由四个成员组成，AE 1 -4。这些AE蛋白存在于大多数细胞中，并通过跨膜阴离子的交换运输来调节细胞内pH和氯离子（Cl-）。带3，命名为AE 1，是红细胞和肾脏远端和集合小管的闰细胞的主要膜蛋白。条带3由911个氨基酸组成，具有两个主要结构域。其在细胞质中的40 kDa N-末端结构域结合红细胞骨架蛋白，并在维持红细胞形状方面发挥作用。而人红细胞Band 3的膜结构域是Cl^-/HCO_3^-逆向转运蛋白。这种交换是血液中CO_2/O_2循环的关键步骤。尽管它们的重要性，关于Band 3的结构信息仍然未知。我们使用X射线晶体学来解决Band 3的三维结构，通过交联固定在向外开放的构象中，分辨率为3.4 μ m。Band 3形成为与Fab片段复合的二聚体。在调光器的中心附近有V形密度。

Anion exchanger (AE) gene family consists of four members, AE1-4. These AE proteins are present in most cells and regulate intracellular pH and chloride (Cl-) by the exchange transport of anions across membranes. Band 3, designated AE1, is the major integral membrane protein of the red blood cells and intercalated cells of the distal and collecting tubules of the kidney. Band 3, consisting of 911 amino acids, has two principal structural domains. Its 40 kDa N-terminal domain in the cytoplasm binds the red blood cell skeleton proteins and has a role in maintaining the shape of erythrocytes. While the membrane domain of human erythrocyte Band3 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 Band3 is still unknown. We used X-ray crystallography to solve the three-dimensional structure of Band3, fixed in an outward-open conformation by cross-linking, at 3.4Å resolution. Band3 are formed as a dimmer in complex with Fab fragments. There are V-shaped densities near the center of the dimmer.