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: London Nature Publishing Group UK 21.03.2024; Nature Publishing Group
• Subjects: 13/109; 14/19; 14/35; 45/77; 631/92/475; 631/92/96; 82/51; 82/58; 82/80; 96/1; 96/34; 96/98; Amino Acids; Cations; Cations - chemistry; Chemical reactions; Chemistry; Cyclization; Humanities and Social Sciences; Indicators and Reagents; Labeling; Lysine; Modulators; multidisciplinary; Oxidation; Oxidation-Reduction; Oxidative Stress; Payloads; Peptides; Phase separation; Proteins; Proteome; Proteomes; Reagents; Residues; Science; Science (multidisciplinary); 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 1 – 3 . Owing to their high nucleophilicity, cysteine and lysine residues are the most common points of attachment for protein bioconjugation chemistry through acid–base reactivity 3 , 4 . 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. Global profiling of hyper-reactive tryptophan sites across whole proteomes using tryptophan chemical ligation by cyclization (Trp-CLiC) reveals a systematic map of tryptophan residues that participate in cation–π interactions, including functional sites that can regulate protein-mediated phase-separation processes.