Oxidative cyclization reagents reveal tryptophan cation-π interactions

• Published in: Nature (London) Vol. 627; no. 8004; pp. 680 - 687
• Main Authors: Xie, Xiao, Moon, Patrick J, Crossley, Steven W M, Bischoff, Amanda J, He, Dan, Li, Gen, Dao, Nam, Gonzalez-Valero, Angel, Reeves, Audrey G, McKenna, Jeffrey M, Elledge, Susanna K, Wells, James A, Toste, F Dean, Chang, Christopher J
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 21.03.2024
• Subjects: Amino acids; Cations; Cations - chemistry; Chemical reactions; Chemistry; Click Chemistry; Cyclization; Indicators and Reagents - chemistry; Labeling; Lysine; Modulators; Oxidation; Oxidation-Reduction; Payloads; Peptides; Peptides - chemistry; Phase separation; Proteins; Proteins - chemistry; Proteome - chemistry; Proteomes; Reagents; Residues; Separation processes; Signal transduction; Solvents; Tryptophan; Tryptophan - chemistry
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/s41586-024-07140-6

Methods for selective covalent modification of amino acids on proteins can enable a diverse array of applications, spanning probes and modulators of protein function to proteomics . Owing to their high nucleophilicity, cysteine and lysine residues are the most common points of attachment for protein bioconjugation chemistry through acid-base reactivity . Here we report a redox-based strategy for bioconjugation of tryptophan, the rarest amino acid, using oxaziridine reagents that mimic oxidative cyclization reactions in indole-based alkaloid biosynthetic pathways to achieve highly efficient and specific tryptophan labelling. We establish the broad use of this method, termed tryptophan chemical ligation by cyclization (Trp-CLiC), for selectively appending payloads to tryptophan residues on peptides and proteins with reaction rates that rival traditional click reactions and enabling global profiling of hyper-reactive tryptophan sites across whole proteomes. Notably, these reagents reveal a systematic map of tryptophan residues that participate in cation-π interactions, including functional sites that can regulate protein-mediated phase-separation processes.