Tunable Cell Surface Proximity Labeling via Photocatalytic and Enzymatic Activation of Fast Bioorthogonal Chemistry

H serves as a quencher during the proximity labeling reaction, and adjusting quencher concentration can attenuate labeling, as demonstrated in vitro on a model protein. Tuning the half-life of the proximity labeling reaction was also studied in live cells to give proteomic data sets with high overlap. Labeling reactions with shorter half-lives enriched fewer total proteins but maintained enrichment of known interactors. We anticipate that this use of fast bioorthogonal reactions will be broadly applicable for studying protein-protein interactions.