Figure 1.

Crosslinking strategy for proteasome subtype identification. Bifunctional proteasome probes, comprised of two peptide epoxyketone proteasome inhibitors coupled by a linker, crosslink different pairs of proteasome catalytic subunits when they are present within the same 20S core complex. Crosslinking efficiency of a particular subunit pair is determined by the subunit selectivity of the two inhibitors as well as the length of the linker by which they are coupled. Following treatment of cell lysates or purified 20S proteasomes with bifunctional proteasome probes, the crosslinked subunit pairs are identified by immunoblotting analysis.