Fig. 1.

A schematic presentation of three different strategies to isolate ubiquitinated substrates. A, The affinity purification strategy using Ub tag that allows purification under proteome denaturing condition. B, Tandem Ub binding domain for endogenous substrate enrichment. C, Poly-Ub chain specific antibody or ubiquitination signature remnant antibody. D, Three different contaminants of either protein precipitation during incubation, nonspecific binders to the matrix, or specific binding proteins to the affinity bait and poly-Ub conjugates exist during purification process.