RIKEN SPring-8 Center, Harima Institute, Hyogo, Japan.
J Struct Biol. 2010 Mar;169(3):406-12. doi: 10.1016/j.jsb.2009.12.009. Epub 2009 Dec 21.
The C-terminal membrane domain of erythrocyte band 3 functions as an anion exchanger. Here, we report the three-dimensional (3D) structure of the membrane domain in an inhibitor-stabilized, outward-open conformation at 18A resolution. Unstained, frozen-hydrated tubular crystals containing the membrane domain of band 3 purified from human red blood cells (hB3MD) were examined using cryo-electron microscopy and iterative helical real-space reconstruction (IHRSR). The 3D image reconstruction of the tubular crystals showed the molecular packing of hB3MD dimers with dimensions of 60 x 110 A in the membrane plane and a thickness of 70A across the membrane. Immunoelectron microscopy and carboxyl-terminal digestion demonstrated that the intracellular surface of hB3MD was exposed on the outer surface of the tubular crystal. A 3D density map revealed that hB3MD consists of at least two subdomains and that the outward-open form is characterized by a large hollow area on the extracellular surface and continuous density on the intracellular surface.
红细胞带 3 的 C 端膜域作为阴离子交换器发挥作用。在这里，我们报告了在抑制剂稳定的、向外开放构象下以 18A 分辨率的膜域的三维（3D）结构。使用冷冻电镜和迭代螺旋实空间重建（IHRSR）检查了从人红细胞中纯化的带 3 的膜域（hB3MD）的未染色、冷冻水合管状晶体。管状晶体的 3D 图像重建显示了 hB3MD 二聚体的分子堆积，其在膜平面上的尺寸为 60 x 110 A，在膜上的厚度为 70A。免疫电子显微镜和羧基末端消化表明 hB3MD 的细胞内表面暴露在管状晶体的外表面上。3D 密度图显示 hB3MD 至少由两个亚结构域组成，并且向外开放形式的特征是细胞外表面上的大空腔区域和细胞内表面上的连续密度。
