Genetically Encoded Quinone Methides Enabling Rapid, Site-Specific, and Photocontrolled Protein Modification with Amine Reagents

• Published in: Journal of the American Chemical Society 2020-10, Vol.142 (40), p.17057-17068
• Main Authors: Liu, Jun, Cheng, Rujin, Van Eps, Ned, Wang, Nanxi, Morizumi, Takefumi, Ou, Wei-Lin, Klauser, Paul C, Rozovsky, Sharon, Ernst, Oliver P, Wang, Lei
• Format: Article
• Language: English
• Subjects: Amines - chemistry; Amino Acids - chemistry; Binding Sites; Electron Spin Resonance Spectroscopy; Indolequinones - chemistry; Kinetics; Photochemical Processes; Protein Conformation; Protein Processing, Post-Translational; Proteins - chemistry; Solvents - chemistry; Spin Labels; Staining and Labeling - methods; Sulfhydryl Compounds - chemistry; Temperature
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.0c06820

Site-specific modification of proteins with functional molecules provides powerful tools for researching and engineering proteins. Here we report a new chemical conjugation method which photocages highly reactive but chemically selective moieties, enabling the use of protein-inert amines for selective protein modification. New amino acids FnbY and FmnbY, bearing photocaged quinone methides (QMs), were genetically incorporated into proteins. Upon light activation, they generated highly reactive QM, which rapidly reacted with amine derivatives. This method features a rare combination of desired properties including fast kinetics, small and stable linkage, compatibility with low temperature, photocontrollability, and widely available reagents. Moreover, labeling via FnbY occurs on the β-carbon, affording the shortest linkage to protein backbone which is essential for advanced studies involving orientation and distance. We installed various functionalities onto proteins and attached a spin label as close as possible to the protein backbone, achieving high resolution in double electron–electron paramagnetic resonance distance measurements.