Figure 1.

ClustalW alignment of the region surrounding the active site of the C. elegans, Drosophila and human UBC proteins. The names of the proteins are color-coded: C. elegans (green), Drosophila (blue), and human (red). Subgroups of UBCs, separated by horizontal lines, have Roman numerals and UBC designations that correspond to branches shown on the dendrogram in Figure 2. The UBC designations (right) for the subgroups indicate the most similar S. cerevisiae UBC. The active-site cysteinyl residue (C) is highlighted in red, and an invariant proline (P, green) and tryptophan (W, yellow) are also indicated. Other features indicated are the UBC tripeptide motif HPN and variants (in yellow and blue) (see text)