UBL shuttle factors bind to ubiquitin-interacting residues of proteasome receptors
hRpn13:hPLIC2 structure reveals an optimized UBL for hRpn13 binding
hPLIC2 sterically blocks Rpn13 binding to K48 diubiquitin, its preferred chain type
Rpn1 T1:Rad23UBL structure reveals Rad23 binding to Helix28/Helix30 of Rpn1 T1