Small ubiquitin-related modifier (SUMO) — which is attached to proteins by a pathway involving the E1 enzyme SAE1, the E2 enzyme UBC9 (also known as UBE21) and an E3 ligase (such as PIAS1 and ...
are post-translationally attached to proteins through a sequential enzymatic cascade that uses an E1 activating enzyme, an E2 conjugating enzyme and an E3 ligase. It was presumed that a single E1 ...