FIG. 5.

Three-dimensional map of functionally important surfaces. The three-dimensional surface of S. cerevisiae RAD6 is used as the map template rotated to the left or right by 60°. The amino terminus is found at the top of the structures. The active-site cysteine is yellow. Conserved solvent-accessible regions are gray. Residues of clear specific functional importance for each E2 based on mutation studies are highlighted in dark green (UBC4), dark magenta (CDC34), or blue (RAD6). Residues of potential importance to E2 specificity according to the criteria described in Results are highlighted in light green (UBC4) or pink (CDC34).