This family of proteins are functionally uncharacterised and are predicted to adopt an all-beta fold [1]. They are often found in gene neighborhoods containing genes for an NlpC peptidase and a Ubiquitin domain predicted to be involved in tail assembly [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