This family consists of several bacterial periplasmic nitrate reductase NapE proteins. Seven genes, napKEFDABC, encoding the periplasmic nitrate reductase system were cloned from the denitrifying phototrophic bacterium Rhodobacter sphaeroides f. sp. denitrificans IL106. NapE is thought to be a transmembrane protein [1].

1: Involvement in denitrification of the napKEFDABC genes encoding the periplasmic nitrate reductase system in the denitrifying phototrophic bacterium Rhodobacter sphaeroides f. sp. denitrificans. Liu HP, Takio S, Satoh T, Yamamoto I; Biosci Biotechnol Biochem 1999;63:530-536. PMID:10227138

2: The napEDABC gene cluster encoding the periplasmic nitrate reductase system of Thiosphaera pantotropha. Berks BC, Richardson DJ, Reilly A, Willis AC, Ferguson SJ; Biochem J 1995;309:983-992. PMID:7639719