Figure 2.

Three major categories of proximity labeling. Each category is illustrated by one or two representative enzyme systems. (a) Binary-candidate PL method using BirA and BAP attached to the bait and prey proteins, respectively. The reaction is induced by biotin and ATP; (b) Peroxidase based PL using Horseradish peroxidase (HRP)-based method on cell surface or APEX in a cellular compartment. The reaction is induced by modified biotin molecules and H₂O₂; (c) Promiscuous PL enzyme illustrated by BioID, which has a working distance around 10 nm. This PL reaction is induced by biotin.