pfam10585: UBA_E1_SCCH (This model is not part of the current CDD release)
Ubiquitin-activating enzyme, SCCH domain
Ubiquitin-activating enzyme (E1 enzyme) activates ubiquitin by first adenylating with ATP its C-terminal glycine residue and thereafter linking this residue to the side chain of a cysteine residue in E1, yielding an ubiquitin-E1 thiolester and free AMP. Later the ubiquitin moiety is transferred to a cysteine residue on one of the many forms of ubiquitin-conjugating enzymes (E2). This domain carries the last of five conserved cysteines that is part of the active site of the enzyme, responsible for ubiquitin thiolester complex formation, the active site being represented by the sequence motif PICTLKNFP. The catalytic cysteine domain contains the E1 active site cysteine, and is divided in two half-domains, FCCH and SCCH, for 'first' and 'second' catalytic cysteine half-domain, respectively. This is the SCCH domain in which resides the catalytic cysteine.
Jiyao W et al.(2023). "The conserved domain database in 2023.",