Figure 2. Structure of Ube2s, Ube2k, and Ube2r.

(A) Domain structure of the E2 enzymes where flexible regions of the E2 enzymes are indicated with lines and domains are shown as coloured boxes. The numbers indicate the number of amino acids in the E2 enzymes. (B) Representative chain-building E2 enzyme (Ube2r; PDB 6NYO) showing the acidic insertion, C-terminal extension, and the helix-loop-helix motif in red. Alpha-helices are numbered, and the N and C terminus are indicated by N and C, respectively.