Figure 3. Cdc34 efficiently generates K48-linked polyubiquitin chains but also inefficiently utilizes Ub K11 and K63. Cdc34 (top) and Cdc34 S139D (bottom) were tested for their ability to generate polyubiquitin chains in the presence of SCFCdc4, with Sic1-K50 as substrate and wild-type Ub (Ub WT), Ub with no lysines (Ub K0) or Ub mutants with a single lysine in the designated position. Lane 1 is a control where E1 was omitted from the reaction. The position of Sic1-K50 substrate, monoubiquitinated Sic1-K50 (Sic1-K50-Ub), diubiquitinated Sic1-K50 (Sic1-K50-Ub2) and polyubiquitinated Sic1-K50 (Sic1 K50-PolyUb) is indicated on the right.