biostudies-literatureBeard HARCUK | Biotechnology and Biological Sciences Research CouncilRCUK | Engineering and Physical Sciences Research CouncilWellcome TrustBiotechnology and Biological Sciences Research CouncilEngineering and Physical Sciences Research Council133https://www.ebi.ac.uk/biostudies/studies/S-EPMC7610391biostudies-literatureUnknown2Ligand-directed protein labelling allows the introduction of diverse chemical functionalities onto proteins without the need for genetically encoded tags. Here we report a method for the rapid labelling of a protein using a ruthenium-bipyridyl (Ru(II)(bpy)<sub>3</sub>)-modified peptide designed to mimic an interacting BH3 ligand within a BCL-2 family protein-protein interactions. Using sub-stoichiometric quantities of (Ru(II)(bpy)<sub>3</sub>)-modified NOXA-B and irradiation with visible light for 1 min, the anti-apoptotic protein MCL-1 can be photolabelled with a variety of functional tags. In contrast with previous reports on Ru(II)(bpy)<sub>3</sub>-mediated photolabelling, tandem mass spectrometry experiments reveal that the labelling site is a cysteine residue of MCL-1. MCL-1 can be laCommunications chemistryPhotocatalytic proximity labelling of MCL-1 by a BH3 ligand.PMC7610391097827/Z/11/A094232BB/M012573/1EP/KO39292/1094232/Z/10/ZEP/N013573EPSRC DTA0978271512523WT094232MAEP/N013573/1Beard HAWalko MGeorge RMWilson AJBon RSHauser JRfalsePhotocatalytic proximity labelling of MCL-1 by a BH3 ligand.Ligand-directed protein labelling allows the introduction of diverse chemical functionalities onto proteins without the need for genetically encoded tags. Here we report a method for the rapid labelling of a protein using a ruthenium-bipyridyl (Ru(II)(bpy)<sub>3</sub>)-modified peptide designed to mimic an interacting BH3 ligand within a BCL-2 family protein-protein interactions. Using sub-stoichiometric quantities of (Ru(II)(bpy)<sub>3</sub>)-modified NOXA-B and irradiation with visible light for 1 min, the anti-apoptotic protein MCL-1 can be photolabelled with a variety of functional tags. In contrast with previous reports on Ru(II)(bpy)<sub>3</sub>-mediated photolabelling, tandem mass spectrometry experiments reveal that the labelling site is a cysteine residue of MCL-1. MCL-1 can be la2019-01-01T00:00:00Z2019 Nov2026-05-01T17:29:49.042Z2024-11-13T06:29:58.89ZS-EPMC76103913376360310.1038/s42004-019-0235-z