Strongly hydrogen-bonded Schiff base and adjoining polyene twisting in the retinal chromophore of schizorhodopsins
Strongly hydrogen-bonded Schiff base and adjoining polyene twisting in the retinal chromophore of schizorhodopsins
复制标题
裂视紫红质视网膜发色团中强氢键希夫碱和相邻多烯扭曲
DOI：
10.1021/acs.biochem.1c00529
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发表时间：
2021
期刊：
影响因子：
2.9
通讯作者：
and Yasuhisa Mizutani
中科院分区：
文献类型：
--
作者：
Tomomi Shionoya;Misao Mizuno;Manish Singh;Hideki Kandori;and Yasuhisa Mizutani
跨膜质子梯度是由细胞中的质子泵产生和维持的。元基因组学研究最近发现了一类新的介于1型视紫红质和日视紫质之间的视紫红质中间体，称为分裂视紫红质(SZRs)。SZR是光驱动的内向质子泵。用全面的共振拉曼光谱表征了四种SZR的非光解状态下视网膜发色团的结构。所有四个SZRs的光谱都表明，视网膜发色团是全反式的和15-反构型的，Schiff碱是质子化的。多烯链在视网膜发色团的中心是平面的，并在质子化的希夫碱附近扭曲。SZRs中的质子化Schiff碱形成了比向外质子泵浦的视紫红质更强的氢键。我们确定质子化的席夫碱的氢键伙伴不是水分子，而是氨基酸残基，推测是螺旋G中的天冬氨酸残基。这些观察结果为深入了解SZRs的内向质子泵机制提供了有价值的见解。
A transmembrane proton gradient is generated and maintained by proton pumps in a cell. Metagenomics studies have recently identified a new category of rhodopsin intermediates between type-1 rhodopsins and heliorhodopsins, named schizorhodopsins (SzRs). SzRs are light-driven inward proton pumps. Comprehensive resonance Raman measurements were conducted to characterize the structure of the retinal chromophore in the unphotolyzed state of four SzRs. The spectra of all four SzRs show that the retinal chromophore is in the all-transand 15-anticonfiguration and that the Schiff base is protonated. The polyene chain is planar in the center of the retinal chromophore and is twisted in the vicinity of the protonated Schiff base. The protonated Schiff base in the SzRs forms a stronger hydrogen bond than that in outward proton-pumping rhodopsins. We determined that the hydrogen-bonding partner of the protonated Schiff base is not a water molecule but an amino acid residue, presumably an Asp residue in helix G. The present observations provide valuable insights into the inward proton-pumping mechanism of SzRs.