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.
Jiyao W et al.(2023). "The conserved domain database in 2023.",