The C-terminal extension of UCHL5 (UCH37) binds to ADRM1, part of the proteasomal 19S regulatory subunit which is itself a subunit of the 26S proteasome. Binding of UCHL5 enhances its DUB activity (Qiu et al. 2006). UCHL5 forms oligomers in solution that have very low DUB activity. Binding with ADRM1 is 1:1, preventing oligomerization of UCHL5 while making the active site of UCHL5 accessible to Ubiquitin (Jiao et al. 2014). When associated with the proteasome, UCHL5 disassembles poly-Ub chains by hydrolyzing the distal ubiquitin from a chain. This dissassembly of the degradation signal from only the distal end of polyubiquitin chains may selectively rescue poorly ubiquitinated or slowly degraded Ub-protein conjugates from proteolysis (Lam et al. 1997).