A member of the E2/UBC superfamily of proteins found in diverse bacteria. Analysis of the active site residues suggest that members of this family are inactive as they lack the characteristic catalytic residues of the E2 enzymes [1,2]. They are usually fused to or in the neighborhood of a multi/poly ubiquitin domain protein. Other proteins of the ubiquitin modification pathway such as the E1 and JAB proteins are also found in its gene neighborhood along with a distinct predicted metal-binding protein.

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