A member of the ubiquitin superfamily that is often fused to the ThiF-like (E1)- ubiquitin activating enzyme and is present in gene neighborhoods with components of the thiamine biosynthesis pathway [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