2D Gel electrophoresis of pulldowns from NEDP1 KO lysate with GST-Zn1+2 followed by Western blot analysis with α-NEDD8 antibody. Some of the 25-kDa NEDD8 band migrates to the same isoelectric point as unconjugated NEDD8 (denoted by white triangle), indicating the species is most likely an unanchored NEDD8 trimer. However, the majority of NEDD8 trimer migrates to multiple spots of lower pI (indicated in the brackets), which suggests that NEDD8 trimers undergo a post-translational modification that either adds a negative charge or blocks a positive charge on the NEDD8 trimer. 