Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furocho, Chikusa, Nagoya, Aichi 464-8601, Japan.
Department of Chemistry, Graduate School of Science, Nagoya University, Furocho, Chikusa, Nagoya, Aichi 464-8601, Japan.
J Phys Chem Lett. 2024 May 30;15(21):5788-5794. doi: 10.1021/acs.jpclett.4c00879. Epub 2024 May 23.
Channelrhodopsin (ChR) and heliorhodopsin (HeR) are microbial rhodopsins with similar structures but different circular dichroism (CD) spectra: ChR shows biphasic negative and positive bands, whereas HeR shows a single positive band. We explored the physicochemical factors underlying these differences through computational methods. Using the exciton model based on first-principles computations, we obtained the CD spectra of ChR and HeR. The obtained spectra indicate that the protein dimer structures and the quantum mechanical treatment of the retinal chromophore and its interacting amino acids are crucial for accurately reproducing the experimental spectra. Further calculations revealed that the sign of the excitonic coupling was opposite between the ChR and HeR dimers, which was attributed to the contrasting second term of the orientation factor between the two retinal chromophores. These findings demonstrate that slight variations in the intermolecular orientation of the two chromophores can result in significant differences in the CD spectral shape.
通道蛋白视紫红质 (ChR) 和噬盐菌视紫红质 (HeR) 是具有相似结构但圆二色性 (CD) 光谱不同的微生物视紫红质：ChR 显示出两相负和正带，而 HeR 显示出单一正带。我们通过计算方法探索了这些差异的理化因素。使用基于第一性原理计算的激子模型，我们获得了 ChR 和 HeR 的 CD 光谱。所得光谱表明，蛋白二聚体结构和对视黄醛发色团及其相互作用氨基酸的量子力学处理对于准确再现实验光谱至关重要。进一步的计算表明，ChR 和 HeR 二聚体之间的激子耦合的符号相反，这归因于两个视黄醛发色团之间取向因子的第二项的对比。这些发现表明，两个发色团的分子间取向的微小变化会导致 CD 光谱形状的显著差异。
