Figure 4.

E3 ubiquitin ligase activity of recombinant AtPUB-ARM proteins. Affinity-purified recombinant AtPUB-ARM proteins were tested for E3 ligase activity in an in vitro ubiquitination assay. The yeast E1 enzyme, E2 enzymes from Arabidopsis (AtUBC) or human (hUBC) and ubiquitin were used in the reactions. The E2 enzyme used in each reaction is indicated above each lane, and the AtPUBARM protein tested is listed below each panel. As a control, the E2 enzyme was omitted from the reaction, and as expected, no ubiquitinated proteins were observed.