an enzyme of the ubiquitin-activating E1 family. Adenylates ubiquitin at its carboxy-terminal glycine residue and thereafter links this residue to the side chain of a cysteine residue in E1, yielding an ubiquitin-E1 thiolester. There are two active sites within the E1 molecule, allowing it to accomodate two ubiquitin moieties at a time, with a new ubiquitin forming an adenylate intermediate as the previous one is transferred to the thiol site. Complements an X-linked mouse temperature-sensitive defect in DNA synthesis, and thus may function in DNA repair. Note: This description may include information from UniProtKB.
Protein type: EC 18.104.22.168; Ubiquitin conjugating system; Ubiquitin ligase