中科院化学所王建平团队报道了超快二维红外光谱识别了微生物感光菌视紫红质胞质表面的结构赖氨酸159。相关研究成果发表在2022年11月18日出版的《美国化学会杂志》。

菌视紫红质（bR）是一种光驱动的微生物受体，赖氨酸159（K159）是其E–F环细胞质（CP）侧的带电残基。然而，由于快速的表面动力学，其构象和功能仍然未知。

通过使用¹³C，¹5N标记的赖氨酸（K）作为同位素探针，研究人员创建了一个特定位点的酰胺-I振动特征（主链羰基延伸）网络，以识别标记的残基对酰胺-I激子带结构的频率贡献。因此，¹³C，¹⁵N赖氨酸标记的bR（uK bR）与未标记的bR（WT bR）中的红移酰胺-I频率可以通过超快二维振动回波红外（2D IR）光谱来区分和检查。

结果表明，K159的骨架羰基位于约1693 cm^–1的高频处，并且在相同频率下具有比本体螺旋酰胺-I模式更短的振动激发态弛豫时间，这表明K159可能具有与E161（bR CP表面上的羧酸盐残基之一）氢键合的γ-圈结构。uK-bR的2D固态NMR研究还揭示了构象依赖性赖氨酸残基，从中发现K159涉及转向基序。K159保持的这种γ-转向结构可能有助于稳定E–F环，并支持E161在bR光循环的后期阶段从体中吸引质子。

该工作中所示的组合光谱方法可用于绘制其他受体和大蛋白的残基特异性局部结构和动力学。

附：英文原文

Title: Ultrafast Two-Dimensional Infrared Spectroscopy Resolved a Structured Lysine 159 on the Cytoplasmic Surface of the Microbial Photoreceptor Bacteriorhodopsin

Author: Rong Hu, Xiaoyan Ding, Pengyun Yu, Xuemei He, Anthony Watts, Xin Zhao, Jianping Wang

Issue&Volume: November 18, 2022

Abstract: Bacteriorhodopsin (bR) is a light-driven microbial receptor, and lysine 159 (K159) is a charged residue on the cytoplasmic (CP) side of its E–F loop. However, its conformation and function remain unknown due to fast surface dynamics. By utilizing a 13C, 15N-labeled lysine (K) as an isotope probe, we created a network of site-specific amide-I vibrational signatures (backbone carbonyl stretch) to identify the frequency contribution of the labeled residues to the amide-I excitonic band structure. Thus, the red-shifted amide-I frequency in the 13C, 15N-lysine-labeled bR (uK-bR) to the unlabeled bR (WT-bR) could be differentiated and examined by ultrafast two-dimensional vibrational echo infrared (2D IR) spectroscopy. Our results showed that the backbone carbonyl of K159 is located at a high frequency of ca. 1693 cm–1 and has a vibrational excited-state relaxation time shorter than the bulk helical amide-I mode at the same frequency, suggesting that K159 may possess a hydrogen-bonded γ-turn structure with E161, one of the carboxylate residues on the CP surface of bR. The 2D solid-state NMR study of uK-bR also revealed conformational dependent lysine residues, from which K159 was found to involve the turn motif. This γ-turn structure maintained by K159 may help to stabilize the E–F loop and support E161 in attracting protons from the bulk during the late stage of the bR photocycle. The combined spectroscopic approach illustrated in this work may be applied to map residue-specific local structures and dynamics of other receptors and large proteins.

DOI: 10.1021/jacs.2c09435

Source: https://pubs.acs.org/doi/10.1021/jacs.2c09435