Murakami Midori, Kitahara Rei, Gotoh Toshiaki, Kouyama Tsutomu
Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Japan.
Acta Crystallogr Sect F Struct Biol Cryst Commun. 2007 Jun 1;63(Pt 6):475-9. doi: 10.1107/S1744309107017423. Epub 2007 May 5.
Rhodopsin, a photoreceptor membrane protein in the retina, is a prototypical member of the G-protein-coupled receptor family. In this study, rhodopsin from the retina of the squid Todarodes pacificus was treated with V8 protease to remove the C-terminal extension. Truncated rhodopsin was selectively extracted from the microvillar membranes using alkyl glucoside in the presence of zinc ions and was then crystallized by the sitting-drop vapour-diffusion method. Of the various crystals obtained, hexagonal crystals grown in the presence of octylglucoside and ammonium sulfate diffracted to 2.8 A resolution. The diffraction data suggested that the crystal belongs to space group P6(2), with unit-cell parameters a = b = 122.1, c = 158.6 A. Preliminary crystallographic analysis, together with linear dichroism results, suggested that the rhodopsin dimers are packed in such a manner that their transmembrane helices are aligned nearly parallel to the c axis.
视紫红质是视网膜中的一种光感受器膜蛋白，是G蛋白偶联受体家族的典型成员。在本研究中，用V8蛋白酶处理太平洋褶柔鱼视网膜中的视紫红质，以去除其C末端延伸部分。在锌离子存在的情况下，使用烷基葡糖苷从微绒毛膜中选择性提取截短的视紫红质，然后通过坐滴气相扩散法使其结晶。在获得的各种晶体中，在辛基葡糖苷和硫酸铵存在下生长的六方晶体的衍射分辨率达到2.8 Å。衍射数据表明该晶体属于空间群P6(2)，晶胞参数a = b = 122.1，c = 158.6 Å。初步晶体学分析以及线性二色性结果表明，视紫红质二聚体以其跨膜螺旋几乎平行于c轴排列的方式堆积。
