Ubiquitin activating enzyme (E1) subunit APPBP1. APPBP1 is part of the heterodimeric activating enzyme (E1), specific for the Rub 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(-like) by C-terminal adenylation, and subsequently forms a highly reactive thioester bond between its catalytic cysteine and Ubls C-terminus. E1 also associates with E2 and promotes ubiquitin transfer to the E2's catalytic cysteine. Post-translational modification by Rub family of ubiquitin-like proteins (Ublps) activates SCF ubiquitin ligases and is involved in cell cycle control, signaling and embryogenesis. ABPP1 contains part of the adenylation domain.
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