Members of this protein family belong to a conserved gene four-gene neighborhood found sporadically in a phylogenetically broad range of bacteria: Nocardia farcinica, Symbiobacterium thermophilum, and Streptomyces avermitilis (Actinobacteria), Geobacillus kaustophilus (Firmicutes), Azoarcus sp. EbN1 and Ralstonia solanacearum (Betaproteobacteria). Proteins in this family average over 1400 amino acids in length. [Hypothetical proteins, Conserved]