Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan.
Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK 74078.
Proc Natl Acad Sci U S A. 2018 Aug 28;115(35):8671-8675. doi: 10.1073/pnas.1806491115. Epub 2018 Aug 13.
Photoactive yellow protein (PYP), from the phototrophic bacterium , is a small water-soluble photoreceptor protein and contains -coumaric acid (CA) as a chromophore. PYP has been an attractive model for studying the physical chemistry of protein active sites. Here, we explore how Raman optical activity (ROA) can be used to extract quantitative information on distortions of the CA chromophore at the active site in PYP. We use C8-CA to assign an intense signal at 826 cm in the ROA spectrum of PYP to a hydrogen out-of-plane vibration of the ethylenic moiety of the chromophore. Quantum-chemical calculations based on density functional theory demonstrate that the sign of this ROA band reports the direction of the distortion in the dihedral angle about the ethylenic C=C bond, while its amplitude is proportional to the dihedral angle. These results document the ability of ROA to quantify structural deformations of a cofactor molecule embedded in a protein moiety.
光激活黄色蛋白（PYP）来源于光合细菌，是一种小的水溶性光受体蛋白，含有 - 香豆酸（CA）作为生色团。PYP 一直是研究蛋白质活性位点物理化学的有吸引力的模型。在这里，我们探讨了拉曼光学活性（ROA）如何用于提取 PYP 活性位点中 CA 生色团的扭曲的定量信息。我们使用 C8-CA 将 PYP 的 ROA 光谱中 826 cm 处的强信号分配给生色团的双键的乙烯部分的氢面外振动。基于密度泛函理论的量子化学计算表明，该 ROA 带的符号报告了关于乙烯 C = C 键的二面角的扭曲方向，而其幅度与二面角成正比。这些结果证明了 ROA 定量测定嵌入蛋白质部分的辅因子分子的结构变形的能力。
