Division of Life Science, Gyeongsang National University, Jinju 52828, Republic of Korea.
Electron Microscopy Research Center, Korea Basic Science Institute, Cheongju 28119, Republic of Korea.
J Microbiol Biotechnol. 2020 May 28;30(5):633-641. doi: 10.4014/jmb.1912.12010.
Microbial rhodopsins are a superfamily of photoactive membrane proteins with covalently bound retinal cofactor. Isomerization of the retinal chromophore upon absorption of a photon triggers conformational changes of the protein to function as ion pumps or sensors. After the discovery of proteorhodopsin in an uncultivated γ-proteobacterium, light-activated proton pumps have been widely detected among marine bacteria and, together with chlorophyll-based photosynthesis, are considered as an important axis responsible for primary production in the biosphere. Rhodopsins and related proteins show a high level of phylogenetic diversity; we focus on a specific class of bacterial rhodopsins containing the 3 omega motif. This motif forms a stack of three nonconsecutive aromatic amino acids that correlates with the B-C loop orientation, and is shared among the phylogenetically close ion pumps such as the NDQ motif-containing sodium-pumping rhodopsin, the NTQ motif-containing chloride-pumping rhodopsin, and some proton-pumping rhodopsins including xanthorhodopsin. Here, we reviewed the recent research progress on these omega rhodopsins, and speculated on their evolutionary origin of functional diversity..
微生物视紫红质是一个超家族的光活性膜蛋白，与共价结合的视黄醛辅因子。视黄醛发色团的光异构化吸收光子后触发蛋白质的构象变化，作为离子泵或传感器发挥作用。在未培养的γ-变形菌中发现保护视紫红质后，光激活的质子泵已广泛存在于海洋细菌中，与基于叶绿素的光合作用一起，被认为是生物圈中初级生产的一个重要轴。视紫红质和相关蛋白显示出高度的系统发育多样性；我们关注含有 3ω 基序的特定类别的细菌视紫红质。该基序形成三个非连续的芳香族氨基酸堆叠，与 B-C 环取向相关，并且在进化上密切相关的离子泵（如含 NDQ 基序的钠离子泵视紫红质、含 NTQ 基序的氯离子泵视紫红质以及一些质子泵视紫红质）中共享，包括黄质视紫红质。在这里，我们回顾了这些ω视紫红质的最新研究进展，并推测了它们功能多样性的进化起源。
