A Ubiquitin-superfamily protein that is present across several bacterial lineages, and found in gene neighborhoods with components of the ubiquitin modification system such as the E1, E2 and JAB proteins, and a novel alpha-helical protein, which is predicted to be enzymatic [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