Supplementary Figure 4: Comparison of the Ube2V2–Ubc13~Ub–RING complex with the MMS2–Ubc13~Ub complex (2GMI) and the UEV1A–Ubc13–CHIP complex (2C2V).

Ube2V2, Ubc13 and donor Ub from the Ube2V2–Ubc13~Ub–RING complex are coloured in blue, green and yellow respectively. The linear fusion dimer of the RING domain of RNF4 is coloured in dark and pale pink. Ub* is coloured in orange. MMS2, Ubc13 and Ub from the MMS2–Ubc13~Ub complex (2GMI) (Eddins, M. J. et al., Nat. Struct. Mol. Biol. 13, 915–20, 2006) are coloured in cyan, grey and magenta respectively. Ubiquitin from the MMS2–Ubc13~Ub complex has been transformed using the symmetry operator X+1/2, –Y+1/2, –Z to show its role as the acceptor ubiquitin.

(a) Ubc13 molecules from both complexes have been superimposed to highlight the different orientation of Ube2V2 and MMS2 with respect to Ubc13 and the resultant effect on the positioning of the acceptor Ub K63.

(b) MMS2 and Ube2V2 molecules from the two complexes have been superimposed to show slight differences in the positioning of the acceptor Ub with respect to MMS2 and Ube2V2. This is likely due to differences in crystal packing.

(c) The Ube2V2–Ubc13~Ub–RING complex is coloured the same as in a. UEV1A and Ubc13 from the UEV1A–Ubc13–CHIP complex (2C2V) (Zhang, M. et al., Mol. Cell. 20, 525–38, 2005) are coloured in dark blue and cyan respectively. One protomer of the CHIP dimer is coloured in grey and the other is coloured in purple. These two structures have been superimposed using Ubc13 showing the similarity between the Ubc13–Ube2V2 and the Ubc13–UEV1A interfaces. Although CHIP is a U-box containing E3 ligase, it adopts the same orientation with respect to the Ubc13–UEV1A complex as the RING domain dimer of RNF4 in the Ube2V2–Ubc13~Ub–RING complex.