Direct evidence for a deprotonated lysine serving as a H- bond acceptor in a photoreceptor protein

• 成果类型: Article
• 署名作者: Nagae, Takayuki; Takeda, Mitsuhiro; Noji, Tomoyasu; Saito, Keisuke; Aoyama, Hiroshi; Miyanoiri, Yohei; Ito, Yutaka; Kainosho, Masatsune; Hirose, Yuu; Ishikita, Hiroshi; Mishima, Masaki
• 署名单位: Tokyo University of Pharmacy & Life Sciences; University of Tokyo; University of Tokyo; University of Osaka; Tokyo Metropolitan University; Toyohashi University of Technology
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-9744
• DOI: 10.1073/pnas.2404472121
• 发表日期: 2024-09-03
• 关键词: spin coupling-constants; hydrogen-bonds; histidine-residues; hydrophobic core; imidazole ring; active-site; nmr; shift; perturbation; conjugation

摘要

Deprotonation or suppression of the pKa of the amino group of a lysine sidechain is a widely recognized phenomenon whereby the sidechain amino group transiently can act as a nucleophile at the active site of enzymatic reactions. However, a deprotonated lysine and its molecular interactions have not been directly experimentally detected. Here, we demonstrate a deprotonated lysine stably serving as an acceptor in a H- bond between the photosensor protein RcaE and its chromophore. Signal splitting and trans- H- bond J coupling observed by NMR spectroscopy provide direct evidence that Lys261 is deprotonated and serves as a H- bond acceptor for the chromophore NH group. Quantum mechanical/molecular mechanical calculations also indicate that this H- bond exists stably. Interestingly, the sidechain amino group of the lysine can act as both donor and acceptor. The remarkable shift in the H- bond characteristics arises from a decrease in solvation, triggered by photoisomerization. Our results provide insights into the dual role of this lysine. This mechanism has broad implications for other biological reactions in which lysine plays a role.