Ubiquitin Enzymes

Ubiquitination is a tightly controlled three-step multienzyme cascades. A ubiquitin-activating enzyme (E1), a ubiquitin-conjugating enzyme (E2), and a ubiquitin ligase (E3) act in a concerted manner to form a covalent bond between ubiquitin and its substrate protein, and thereby write the ubiquitin code. In detail, this process is initiated by a family of mechanistically and structurally-related E1 enzymes. The E1s serve to activate ubiquitin/UBLs through C-terminal adenylation and thiol transfer and to coordinate the utilization of ubiquitin/UBLs in specific downstream pathways by charging cognate E2 enzymes, which then interact with the downstream ubiquitylation machinery to coordinate modification of the target.