HOIP based peptides bind to HOIP-UBA over HOIL-UBL. (A) Representative gels from fluorescent hrCNE. Bands representing FITC labeled HOIP WT peptide in absence (lanes 1–4), or presence (lanes 6, 8, and 10) of specified recombinant proteins. Lanes 5, 7, and 9 were loaded with each of the recombinant proteins, but without FITC-peptide. (B) Representative blot against total ubiquitin of the HOIL-UBL and HOIP-UBA competition assays. Petit-LUBAC and the indicated peptides were incubated in presence or absence of 90 μg/mL of HOIL-UBL or HOIP-UBA.