Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan.
Sci Rep. 2018 Sep 3;8(1):13123. doi: 10.1038/s41598-018-31370-0.
Bacteriorhodopsin (bR) of Halobacterium salinarum is a membrane protein that acts as a light-driven proton pump. bR and its homologues have recently been utilized in optogenetics and other applications. Although the structures of those have been reported so far, the resolutions are not sufficient for elucidation of the intrinsic structural features critical to the color tuning and ion pumping properties. Here we report the accurate crystallographic analysis of bR in the ground state. The influence of X-rays was suppressed by collecting the data under a low irradiation dose at 15 K. Consequently, individual atoms could be separately observed in the electron density map at better than 1.3 Å resolution. Residues from Thr5 to Ala233 were continuously constructed in the model. The twist of the retinal polyene was determined to be different from those in the previous models. Two conformations were observed for the proton release region. We discuss the meaning of these fine structural features.
盐沼盐杆菌视紫红质（bR）是一种膜蛋白，可作为光驱动质子泵。bR 及其同源物最近已被应用于光遗传学和其他应用。尽管迄今已报道了这些结构，但分辨率不足以阐明对颜色调谐和离子泵送特性至关重要的内在结构特征。在这里，我们报告了在基态下 bR 的精确晶体学分析。通过在 15 K 下以低辐照剂量收集数据，抑制了 X 射线的影响。因此，在优于 1.3Å 的分辨率下，可以单独观察到电子密度图中的单个原子。在模型中连续构建了从 Thr5 到 Ala233 的残基。确定视黄醛聚烯的扭曲与以前的模型不同。观察到质子释放区域的两种构象。我们讨论了这些精细结构特征的意义。
