Extended Data Fig. 2: The ubiquitination pathway and SUMOylation.
a, Mechanism of ubiquitin-like protein (Ubl) conjugation. Attachment of a Ubl to a substrate is initiated by an activating enzyme (E1) in an ATP-dependent process, forming a Ubl~E1 thioester intermediate. The Ubl is then transferred to a conjugating enzyme (E2) via transthioesterification, and lastly attached to the acceptor lysine of a target protein. The last step is often assisted by specific E3 ligases, for example RING type E3s (depicted), which bring together the Ubl~E2 thioester intermediate and a given substrate, contributing to target specificity and high reactivity. Deubiquitinases (DUBs) can hydrolyse the isopeptide bond. b, SUMOylation of RanGAP1 with rhodamine-labeled SUMO3 using E1, ATP and Ubc9, in the absence of an E3 ligase. c, In-gel fluorescence of SDS–PAGE analysis of b after 1 h reaction time in the presence (filled circle) or absence (hollow circle) of ATP. n = 2 independent experiments with similar results, representative data shown. Full gel image is available in the Source Data file.
