The counterion-retinylidene Schiff base interaction of an invertebrate rhodopsin rearranges upon light activation
The counterion-retinylidene Schiff base interaction of an invertebrate rhodopsin rearranges upon light activation
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DOI：
10.1038/s42003-019-0409-3
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发表时间：
2019-05-13
影响因子：
5.9
通讯作者：
Terakita, Akihisa
中科院分区：
文献类型：
--
作者：
Nagata, Takashi;Koyanagi, Mitsumasa;Terakita, Akihisa
动物利用光敏蛋白质--视紫红质--来感知光线，视紫红质含有一种发色团--视网膜色素，这种色素本身就能吸收紫外线。可见光的敏感性主要取决于亚视黄基席夫碱（SB）的质子化，这需要一个带负电荷的氨基酸残基-稳定。人们对各种视紫红质中最常见的拮抗剂Glu 181的功能知之甚少。在这里，我们表明，在蜘蛛视觉视紫红质，直向同源的哺乳动物黑视蛋白相关的昼夜节律，Glu 181 counterfunctions可能通过形成一个氢键网络，其中Ser 186是一个关键的调解人的Glu 181-SB相互作用。我们还建议，光激活后，Glu 181-SB相互作用重排，而Ser 186改变其贡献。这与脊椎动物视紫红质Glu 113的功能相反，它与SB形成盐桥。我们的研究结果揭示了与无脊椎动物视觉和脊椎动物非视觉光感受相关的可见光敏感性的分子机制。
Animals sense light using photosensitive proteins-rhodopsins-containing a chromophore-retinal-that intrinsically absorbs in the ultraviolet. Visible light-sensitivity depends primarily on protonation of the retinylidene Schiff base (SB), which requires a negatively-charged amino acid residue-counterion-for stabilization. Little is known about how the most common counterion among varied rhodopsins, Glu181, functions. Here, we demonstrate that in a spider visual rhodopsin, orthologue of mammal melanopsins relevant to circadian rhythms, the Glu181 counterion functions likely by forming a hydrogen-bonding network, where Ser186 is a key mediator of the Glu181-SB interaction. We also suggest that upon light activation, the Glu181-SB interaction rearranges while Ser186 changes its contribution. This is in contrast to how the counterion of vertebrate visual rhodopsins, Glu113, functions, which forms a salt bridge with the SB. Our results shed light on the molecular mechanisms of visible light-sensitivity relevant to invertebrate vision and vertebrate non-visual photoreception.