An uncharacterised alpha/beta domain fused to E1 proteins. This protein is usually present in gene neighbourhoods with genes encoding a JAB protein and a predicted metal-binding protein. In related E1 proteins, the E1-N domain is replaced by an E2/UBC superfamily 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