To understand cellular processes at molecular levels, elucidation of protein-protein interactions occurring at a specific location in living cells is required. We have developed a proximity labeling method mediated by the enzyme-mediated activation of radical source (EMARS) reaction, which features a radical formation from labeling reagents by horseradish peroxidase (HRP) set on a molecule of interest (probed molecule). Proximal molecules are covalently labeled with a tag conjugated with the labeling reagent. Here we describe protocols for preparation of a labeling reagent, labeling of neighboring proteins of the probed molecule in living cells, and identification of the labeled proteins.
Keywords: Antibody array; Fluorescein-tyramide; HRP; Mass spectrometry; Radical.