A divergent member of the E2/UBC superfamily of proteins found in bacteria. Members of the family contain a conserved cysteine in place of the histidine of the classical E2/UBC proteins [1,2]. Members of this family are usually fused to an E1 domain at their C-terminus. The protein is usually in the gene neighborhood of a gene encoding a JAB peptidase and another encoding a predicted metal binding domain [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