UBA1 (UBA1 is the acronym for "Ubiquitin Like Modifier Activating Enzyme 1") is a protein-coding gene located on chromosome Xp11.3 ( Lee I et al. 2008). The gene is part of a gene cluster on chromosome Xp11.23. Alternatively spliced transcript variants encoding the same protein have been described. An important paralog of this gene is UBA7.
The enzyme encoded by the UBA1 gene (E1) is a 110-120 kDa monomeric protein. E1 consists of 4 building blocks:
- Adenylation domain consisting of two MoeB/ThiF homology motifs, the latter of which binds ATP and Ub.
- catalytic cysteine half-domains containing the E1 activity center cysteine inserted into each of the adenylation domains
- Four-helix bundle representing a second insertion in the inactive adenylation domain immediately following the first catalytic cysteine half-domain
- C-terminal ubiquitin fold domain that recruits specific E2.