SCCRO5 augments cullin neddylation. A, Western blot analysis of the indicated cullins on products of an in vitro neddylation reaction using HeLa lysates as a source for Cullin-ROC1 complexes supplemented with a gradient of SCCRO5, which shows a dose-dependent increase in neddylation of Cul1, Cul2, and Cul3 with the addition of recombinant SCCRO5. B, Western blot analysis of Cul1 on products of an in vitro neddylation reaction with (lanes 5-8) or without (lanes 1-4) the addition of SCCRO5, which shows enhanced efficiency of Cul1 neddylation by SCCRO5. C, Western blot analysis of Cul3 on products of an in vitro neddylation reaction with concentration gradients of SCCRO5, SCCRO5_Δ1-46, SCCRO5_D225N, or SCCRO5_E226A (quantities in pmol), which shows a dose-dependent increase in neddylation of Cul3 with SCCRO5 and SCCRO5_Δ1-46 but not with SCCRO5_D225N or SCCRO5_E226A.