This domain is found mainly in the Cyanobacteria and in Proteobacteria such as the nitrogen-fixing bacterium Azotobacter vinelandii. It is found in Nif11, a protein described in Azotobacter as linked to nitrogen fixation [1]. It also constitutes a leader peptide in Nif11-derived peptides (N11P), which are thought to be post-translationally modified microcins derived from a putative nitrogen-fixing protein [2]. N11P sequences have a classic leader peptide cleavage motif, usually Gly-Gly, which marks the end of family-wide similarity area and the beginning of a low-complexity region rich in Cys, Gly and Ser [2].

1: Physical and genetic map of the major nif gene cluster from Azotobacter vinelandii. Jacobson MR, Brigle KE, Bennett LT, Setterquist RA, Wilson MS, Cash VL, Beynon J, Newton WE, Dean DR; J Bacteriol 1989;171:1017-1027. PMID:2644218

2: Expansion of ribosomally produced natural products: a nitrile hydratase- and Nif11-related precursor family. Haft DH, Basu MK, Mitchell DA; BMC Biol. 2010;8:70. PMID:20500830