biostudies-literatureRaynal LWellcome Trust62787-62793https://www.ebi.ac.uk/biostudies/studies/S-EPMC12756790biostudies-literatureUnknown10(51)Proximity catalysis exploits ligand binding for localized, catalytic protein modification. In this work, we introduce catalyst-functionalized peptides as versatile ligands for this approach. Through the functionalization of target-binding peptides with pyridinium oxime catalysts, we show that model proteins can be site-selectively modified with a variety of <i>N</i>-acyl-<i>N</i>-alkylsulfonamide reagents to introduce common functionalities, including fluorophores and affinity handles to the protein surface. Critically, we show that simple changes to the peptide-catalyst structure, moving the pyridinium oxime from the N- to C-terminus, alter the site of modification. This opens up possibilities to develop peptide libraries for a particular target protein and subsequently tuning the modificACS omegaSite-Selective Protein Modification via Peptide-Directed Proximity Catalysis.PMC12756790221349/Z/20/ZJohnson SDNabarro JRaynal LMiller LMSpicer CDMoul SLDowle AAMasithi PFascione MAfalseSite-Selective Protein Modification via Peptide-Directed Proximity Catalysis.Proximity catalysis exploits ligand binding for localized, catalytic protein modification. In this work, we introduce catalyst-functionalized peptides as versatile ligands for this approach. Through the functionalization of target-binding peptides with pyridinium oxime catalysts, we show that model proteins can be site-selectively modified with a variety of <i>N</i>-acyl-<i>N</i>-alkylsulfonamide reagents to introduce common functionalities, including fluorophores and affinity handles to the protein surface. Critically, we show that simple changes to the peptide-catalyst structure, moving the pyridinium oxime from the N- to C-terminus, alter the site of modification. This opens up possibilities to develop peptide libraries for a particular target protein and subsequently tuning the modific2025-01-01T00:00:00Z2025 Dec2026-06-06T10:42:35.384Z2026-05-29T03:12:34.017ZS-EPMC127567904148725610.1021/acsomega.5c07883