The highly similar UbcH6 and UbcH8 E2 enzymes interact with different RING E3 domains cohorts.

<p><b>A.</b> Sequence alignment of human UbcH6 (UBE2E1) and UbcH8 (UBE2E2). Secondary structures and E3-interface regions (H1, L1 and L2) are indicated. Arrows indicate E2-specific residues; asterisks indicate conserved residues involved in bridging. N-terminal extensions are indicated as shaded. <b>B.</b> E3-interaction profiles of <i>wt</i> UbcH6, UbcH8 and UbcH8 D113E (see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1002754#s4" target="_blank">Materials and Methods</a> section for details).