title: Tandem and single genes of three membrane-bound nitrate transporters in the nar gene cluster of the moderately halophilic denitrifier, Halomonas halodenitrificans.
abstract: We identified the genes encoding the membrane-bound nitrate reductase (Nar) from the moderate halophile, Halomonas halodenitrificans, and examined the structure of the gene cluster. Screening of a H. halodenitrificans genomic DNA library in lambda EMBL3 phage by chromosome walking revealed that the region adjacent to the nor gene cluster encoding nitric oxide (NO) reductase contains three nitrate transporters: tandem narK2 and narK1.1 genes and a single narK1.2 gene encoded in opposite directions. NarK1.1 and NarK1.2 proteins, which have 12 putative membrane-spanning helices, were classified as type I NarK, whereas NarK2, which has 14 putative membrane-spanning helices, was classified as a type II NarK. NarK1.1 and NarK2 proteins were considered to be functionally and structurally linked in the cytoplasmic membrane. The systems regulating the expression of the tandem narK2K1.1 gene and the single narK1.2 gene were found to be different. Further, binding sites for NarL and Fnr-like proteins are present in the promoter region of the narK2 gene.
authors.affiliation: Division of Biological Structure, Graduate School of Natural Sciences, Nagoya City University, Mizuho 1, Nagoya 467-8501, Japan. sakurai@nsc.nagoya-cu.ac.jp
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Sakurai
authors.forename: Azumi
authors.initials: A
authors.lastname: Asada
authors.forename: Shuhei
authors.initials: S
authors.lastname: Mano
authors.forename: Kunishige
authors.initials: K
authors.lastname: Kataoka
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sakurai
mesh_terms: D027321:Anion Transport Proteins / Q000235:genetics* / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D020632:Halomonas / Q000235:genetics* / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family; D000091285:Nitrate Transporters; D009566:Nitrates / Q000378:metabolism*
chemical_list: D027321:Anion Transport Proteins; D001426:Bacterial Proteins; D008565:Membrane Proteins; D000091285:Nitrate Transporters; D009566:Nitrates