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Ubiquitin-conjugating enzyme E2, catalytic (UBCc) domain of ubiquitin conjugating enzyme E2 S and related domains The E2S subfamily includes mammalian ubiquitin-conjugating enzymes E2 S (UBE2S/E2EPF), plant ubiquitin-conjugating enzyme E2 22 (UBC22), and similar proteins. They are ubiquitin-conjugating enzymes (EC2.3.2.23) that accept ubiquitin from the E1 complex and catalyze the covalent attachment to other proteins. UBE2S catalyzes 'Lys-11'-linked polyubiquitination. It acts as an essential factor of the anaphase promoting complex/cyclosome (APC/C), a cell cycle-regulated ubiquitin ligase that controls progression through mitosis. UBE2S acts by specifically elongating 'Lys-11'-linked polyubiquitin chains initiated by the E2 enzyme UBE2C/UBCH10 on APC/C substrates, enhancing the degradation of APC/C substrates by the proteasome and promoting mitotic exit. It also acts by elongating ubiquitin chains initiated by the E2 enzyme UBE2D1/UBCH5 in vitro; it is however unclear whether UBE2D1/UBCH5 acts as an E2 enzyme for the APC/C in vivo. UBE2S is also involved in ubiquitination and subsequent degradation of VHL, resulting in an accumulation of HIF1A. In vitro, it can promote polyubiquitination using all 7 ubiquitin Lys residues, except 'Lys-48'-linked polyubiquitination.
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