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Ubiquitin activating enzyme (E1) subunit Aos1. Aos1 is part of the heterodimeric activating enzyme (E1), specific for the SUMO family of ubiquitin-like proteins (Ubls). E1 enzymes are part of a conjugation cascade to attach Ub or Ubls, covalently to substrate proteins consisting of activating (E1), conjugating (E2), and/or ligating (E3) enzymes. E1 activates ubiquitin by C-terminal adenylation, and subsequently forms a highly reactive thioester bond between its catalytic cysteine and Ubls C-terminus. The E1 also associates with E2 and promotes ubiquitin transfer to the E2's catalytic cysteine. Post-translational modification by SUMO family of ubiquitin-like proteins (Ublps) is involved in cell division, nuclear transport, the stress response and signal transduction. Aos1 contains part of the adenylation domain.
Jiyao W et al.(2023). "The conserved domain database in 2023.",