I Weblogos of the HTH motifs of UBE2S, UBE2C, UBE2D, and UBE2R. Residues colored according to their average net negative (red) or positive (blue) charge. Residues of interest on UBE2S, UBE2C, UBE2D, and UBE2R are labeled. UBE2R is extended to show conservation of D143, used in Fig 4. 