Activates ubiquitin by first adenylating its C-terminal glycine residue with ATP, and thereafter linking this residue to the side chain of a cysteine residue in E1, yielding an ubiquitin- E1 thioester and free AMP. Specific for ubiquitin, does not activate ubiquitin-like peptides. Differs from UBE1 in its specificity for substrate E2 charging. Does not charge cell cycle E2s, such as CDC34. Essential for embryonic development. Required for UBD/FAT10 conjugation. Isoform 2 may play a key role in ubiquitin system and may influence spermatogenesis and male fertility. Belongs to the ubiquitin-activating E1 family. 4 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.
Protein type: EC 188.8.131.52; Ubiquitin conjugating system; Ubiquitin ligase