Crystal structure of heliorhodopsin
Crystal structure of heliorhodopsin
复制标题
DOI：
10.1038/s41586-019-1604-6
复制
发表时间：
2019-10-03
期刊：
影响因子：
64.8
通讯作者：
Nureki, Osamu
中科院分区：
文献类型：
--
作者：
Shihoya, Wataru;Inoue, Keiichi;Nureki, Osamu
太阳神(HERS)是最近利用功能元基因组学(1)发现的视紫红质家族。它们广泛存在于细菌、古菌、藻类和藻类病毒中(2，3)。尽管她的HERS有7个预测的跨膜螺旋和一个全跨视网膜发色团，就像1型(微生物)视紫红质一样，但它们与1型和2型(动物)视紫红质的序列同源性不到15%。与其他视紫红质相比，她的视紫红质在膜中也显示出相反的取向。由于缺乏结构信息，人们对HERS的整体折叠和光活化机制知之甚少。在这里，我们展示了来自未培养的热浆菌类考古子SG8-52-1(GenBank序列ID LSSD01000000)的HER的2.4埃分辨率结构。结构和生物物理分析揭示了HERS和1型微生物视紫红质之间的异同。HER的整体皱折与细菌视紫红质相似。与1型视紫红质一样，HER中的线性疏水口袋容纳视网膜构型和异构化，尽管构成口袋的大部分残基是发散的。疏水残基填满了HER细胞外半部的空隙，阻止了质子和离子的渗透。该结构揭示了在视网膜生色团的β-紫罗兰酮环上方有一个意想不到的侧向窗口，这在从环境来源捕获视网膜方面具有关键作用。我们的研究增加了对HERS功能的理解，以及微生物视紫红质之间的结构相似性和多样性。
Heliorhodopsins (HeRs) are a family of rhodopsins that was recently discovered using functional metagenomics(1). They are widely present in bacteria, archaea, algae and algal viruses(2,3). Although HeRs have seven predicted transmembrane helices and an all-trans retinal chromophore as in the type-1 (microbial) rhodopsin, they display less than 15% sequence identity with type-1 and type-2 (animal) rhodopsins. HeRs also exhibit the reverse orientation in the membrane compared with the other rhodopsins. Owing to the lack of structural information, little is known about the overall fold and the photoactivation mechanism of HeRs. Here we present the 2.4-angstrom-resolution structure of HeR from an uncultured Therm oplasmatales archaeon SG8-52-1 (GenBank sequence ID LSSD01000000). Structural and biophysical analyses reveal the similarities and differences between HeRs and type-1 microbial rhodopsins. The overall fold of HeR is similar to that of bacteriorhodopsin. A linear hydrophobic pocket in HeR accommodates a retinal configuration and isomerization as in the type-1 rhodopsin, although most of the residues constituting the pocket are divergent. Hydrophobic residues fill the space in the extracellular half of HeR, preventing the permeation of protons and ions. The structure reveals an unexpected lateral fenestration above the beta-ionone ring of the retinal chromophore, which has a critical role in capturing retinal from environment sources. Our study increases the understanding of the functions of HeRs, and the structural similarity and diversity among the microbial rhodopsins.