A member of the E2/UBC superfamily of proteins found in several bacteria. The active site residues are very similar to the eukaryotic E2 proteins [1,2]. Members of this family are usually fused to E1 and JAB domains C-terminal to the E2 domain. The protein is usually in the gene neighborhood of a gene encoding a distinct metallobetalactamase family protein [1].

1: The prokaryotic antecedents of the ubiquitin-signaling system and the early evolution of ubiquitin-like beta-grasp domains. Iyer LM, Burroughs AM, Aravind L; Genome Biol. 2006;7:R60. PMID:16859499

2: Anatomy of the E2 ligase fold: implications for enzymology and evolution of ubiquitin/Ub-like protein conjugation. Burroughs AM, Jaffee M, Iyer LM, Aravind L; J Struct Biol. 2008;162:205-218. PMID:18276160