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A photoproduct of DXCF cyanobacteriochromes without reversible Cys ligation is destabilized by rotating ring twist of the chromophore.
Photochemical & Photobiological Sciences ( IF 2.7 ) Pub Date : 2020-07-23 , DOI: 10.1039/d0pp00208a Keiji Fushimi 1 , Takumi Matsunaga 2 , Rei Narikawa 3
Photochemical & Photobiological Sciences ( IF 2.7 ) Pub Date : 2020-07-23 , DOI: 10.1039/d0pp00208a Keiji Fushimi 1 , Takumi Matsunaga 2 , Rei Narikawa 3
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Cyanobacteriochrome photoreceptors (CBCRs) ligate linear tetrapyrrole chromophores via their first (canonical) Cys residue and show reversible photoconversion triggered by light-dependent Z/E isomerization of the chromophore. Among the huge repertoire of CBCRs, DXCF CBCRs contain a second Cys residue within the highly conserved Asp-Xaa-Cys-Phe (DXCF) motif. In the typical receptors, the second Cys covalently attaches to the 15Z-chromophore in the dark state and detaches from the 15E-chromophore in the photoproduct state, whereas atypical ones that lack reversible ligation activity show red-shifted absorption in the dark state due to a more extended π-conjugated system. Moreover, some DXCF CBCRs show blue-shifted absorption in the photoproduct state due to the twisted geometry of the rotating ring. During the process of rational color tuning of a certain DXCF CBCR, we unexpectedly found that twisted photoproducts of some variant molecules showed dark reversion to the dark state, which prompted us to hypothesize that the photoproduct is destabilized by the twisted geometry of the rotating ring. In this study, we comprehensively examined the photoproduct stability of the twisted and relaxed molecules derived from the same CBCR scaffolds under dark conditions. In the DXCF CBCRs lacking reversible ligation activity, the twisted photoproducts showed faster dark reversion than the relaxed ones, supporting our hypothesis. By contrast, in the DXCF CBCRs exhibiting reversible ligation activity, the twisted photoproducts showed no detectable photoconversion. Reversible Cys adduct formation thus results in drastic rearrangement of the protein–chromophore interaction in the photoproduct state, which would contribute to the previously unknown photoproduct stability.
中文翻译：
DXCF氰基细菌色素无可逆Cys连接的光产物通过发色团的旋转环扭曲而不稳定。
蓝细菌色素光感受器（CBCR）通过其第一个（规范）Cys残基连接线性四吡咯发色团，并显示出由光依赖的发色团的Z / E异构化引发的可逆光转化。在CBCR的所有库中，DXCF CBCR在高度保守的Asp-Xaa-Cys-Phe（DXCF）主题中包含第二个Cys残基。在典型的受体中，第二个Cys在黑暗状态下共价附于15 Z-发色团，并与15 E脱离-处于发色状态的发色团，而缺乏可逆连接活性的非典型发色团由于扩展的π共轭体系而在暗态下显示出红移吸收。此外，由于旋转环的扭曲几何形状，某些DXCF CBCR在光产品状态下显示蓝移吸收。在对某个DXCF CBCR进行合理的颜色调整的过程中，我们意外地发现某些变体分子的扭曲光产物显示出暗态回复到暗态，这促使我们假设该光产物由于旋转环的扭曲几何形状而变得不稳定。在这项研究中，我们全面检查了在黑暗条件下源自相同CBCR支架的扭曲和松弛分子的光产物稳定性。在缺乏可逆连接活性的DXCF CBCR中，扭曲的光产品显示出比松弛光产品更快的暗色回复，支持了我们的假设。相反，在表现出可逆的连接活性的DXCF CBCR中，扭曲的光产物未显示可检测的光转化。因此，可逆的Cys加合物的形成导致光产物状态下蛋白质与生色团相互作用的剧烈重排，这将有助于以前未知的光产物稳定性。
更新日期：2020-07-23
中文翻译：
DXCF氰基细菌色素无可逆Cys连接的光产物通过发色团的旋转环扭曲而不稳定。
蓝细菌色素光感受器（CBCR）通过其第一个（规范）Cys残基连接线性四吡咯发色团，并显示出由光依赖的发色团的Z / E异构化引发的可逆光转化。在CBCR的所有库中，DXCF CBCR在高度保守的Asp-Xaa-Cys-Phe（DXCF）主题中包含第二个Cys残基。在典型的受体中，第二个Cys在黑暗状态下共价附于15 Z-发色团，并与15 E脱离-处于发色状态的发色团，而缺乏可逆连接活性的非典型发色团由于扩展的π共轭体系而在暗态下显示出红移吸收。此外，由于旋转环的扭曲几何形状，某些DXCF CBCR在光产品状态下显示蓝移吸收。在对某个DXCF CBCR进行合理的颜色调整的过程中，我们意外地发现某些变体分子的扭曲光产物显示出暗态回复到暗态，这促使我们假设该光产物由于旋转环的扭曲几何形状而变得不稳定。在这项研究中，我们全面检查了在黑暗条件下源自相同CBCR支架的扭曲和松弛分子的光产物稳定性。在缺乏可逆连接活性的DXCF CBCR中，扭曲的光产品显示出比松弛光产品更快的暗色回复，支持了我们的假设。相反，在表现出可逆的连接活性的DXCF CBCR中，扭曲的光产物未显示可检测的光转化。因此，可逆的Cys加合物的形成导致光产物状态下蛋白质与生色团相互作用的剧烈重排，这将有助于以前未知的光产物稳定性。
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