title: Role of Nitrosomonas europaea NitABC iron transporter in the uptake of Fe3+-siderophore complexes.
abstract: Nitrosomonas europaea has a single three-gene operon (nitABC) encoding an iron ABC transporter system (NitABC). Phylogenetic analysis clustered the subunit NitB with Fe(3+)-ABC transporter permease components from other organisms. The N. europaea strain deficient in nitB (nitB::kan) grew well in either Fe-replete or Fe-limited media and in Fe-limited medium containing the catecholate-type siderophore, enterobactin or the citrate-based dihydroxamate-type siderophore, aerobactin. However, the nitB::kan mutant strain was unable to grow in Fe-limited media containing either the hydroxamate-type siderophores, ferrioxamine and ferrichrome or the mixed-chelating type siderophore, pyoverdine. Exposure of N. europaea cells to a ferrichrome analog coupled to the fluorescent moiety naphthalic diimide (Fhu-NI) led to increase in fluorescence in the wild type but not in nitB::kan mutant cells. Spheroplasts prepared from N. europaea wild type exposed to Fhu-NI analog retained the fluorescence, while spheroplasts of the nitB::kan mutant were not fluorescent. NitABC transports intact Fe(3+)-ferrichrome complex into the cytoplasm and is an atypical ABC type iron transporter for Fe(3+) bound to ferrioxamine, ferrichrome or pyoverdine siderophores into the cytoplasm. The mechanisms to transport iron in either the Fe(3+) or Fe(2+) forms or Fe(3+) associated with enterobactin or aerobactin siderophores into the cell across the cytoplasmic membrane are as yet undetermined.
authors.affiliation: Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, USA.
authors.forename: Neeraja
authors.initials: N
authors.lastname: Vajrala
authors.forename: Luis A
authors.initials: LA
authors.lastname: Sayavedra-Soto
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Bottomley
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Arp
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D003676:Deferoxamine / Q000378:metabolism; D004758:Enterobactin / Q000378:metabolism; D005290:Ferric Compounds / Q000378:metabolism; D005291:Ferrichrome / Q000378:metabolism; D005798:Genes, Bacterial; D006877:Hydroxamic Acids / Q000378:metabolism; D016296:Mutagenesis; D009154:Mutation; D043370:Nitrosomonas europaea / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D009842:Oligopeptides / Q000378:metabolism; D009876:Operon; D010802:Phylogeny; D012329:RNA, Bacterial / Q000235:genetics; D017262:Siderophores / Q000378:metabolism*
chemical_list: D018528:ATP-Binding Cassette Transporters; D001425:Bacterial Outer Membrane Proteins; D005290:Ferric Compounds; D006877:Hydroxamic Acids; D009842:Oligopeptides; D012329:RNA, Bacterial; D017262:Siderophores; D005291:Ferrichrome; C031819:aerobactin; D004758:Enterobactin; C002577:ferrioxamine B; C042453:pyoverdin; D003676:Deferoxamine