title: Roles of Agrobacterium tumefaciens membrane-bound ferritin (MbfA) in iron transport and resistance to iron under acidic conditions.
abstract: Agrobacterium tumefaciens membrane-bound ferritin (MbfA) is a member of the erythrin (Er)-vacuolar iron transport family. The MbfA protein has an Er or ferritin-like domain at its N terminus and has been predicted to have five transmembrane segments in its C-terminal region. Analysis of protein localization using PhoA and LacZ reporter proteins supported the view that the N-terminal di-iron site is located in the cytoplasm whilst the C-terminal end faces the periplasm. An A. tumefaciens mbfA mutant strain had 1.5-fold higher total iron content than the WT strain. Furthermore, multi-copy expression of mbfA reduced total iron content two- and threefold in WT and mbfA mutant backgrounds, respectively. These results suggest that MbfA may function as an iron exporter rather than an iron storage protein. The mbfA mutant showed 10-fold increased sensitivity to the iron-activated antibiotic streptonigrin, implying that the mutant had increased accumulation of intracellular free iron. Growth of the mbfA mutant was reduced in the presence of high iron under acidic conditions. The expression of mbfA was induced highly in cells grown in iron-replete medium at pH 5.5, further supporting the view that mbfA is involved in the response to iron under acidic conditions. A. tumefaciens MbfA may play a protective role against increased free iron in the cytoplasm through iron binding and export, thus preventing iron-induced toxicity via the Fenton reaction.
authors.affiliation: Center of Excellence on Environmental Health and Toxicology (EHT), Ministry of Education, Bangkok, Thailand.|Applied Biological Sciences, Chulabhorn Graduate Institute, Lak Si, Bangkok 10210, Thailand.
authors.forename: Sakkarin
authors.initials: S
authors.lastname: Bhubhanil
authors.affiliation: Environmental Toxicology, Chulabhorn Graduate Institute, Lak Si, Bangkok 10210, Thailand.|Center of Excellence on Environmental Health and Toxicology (EHT), Ministry of Education, Bangkok, Thailand.
authors.forename: Jareeya
authors.initials: J
authors.lastname: Chamsing
authors.affiliation: Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand.|Environmental Toxicology, Chulabhorn Graduate Institute, Lak Si, Bangkok 10210, Thailand.|Center of Excellence on Environmental Health and Toxicology (EHT), Ministry of Education, Bangkok, Thailand.
authors.forename: Panida
authors.initials: P
authors.lastname: Sittipo
authors.affiliation: Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand.|Environmental Toxicology, Chulabhorn Graduate Institute, Lak Si, Bangkok 10210, Thailand.|Center of Excellence on Environmental Health and Toxicology (EHT), Ministry of Education, Bangkok, Thailand.
authors.forename: Paweena
authors.initials: P
authors.lastname: Chaoprasid
authors.affiliation: Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand.|Center of Excellence on Environmental Health and Toxicology (EHT), Ministry of Education, Bangkok, Thailand.|Applied Biological Sciences, Chulabhorn Graduate Institute, Lak Si, Bangkok 10210, Thailand.
authors.forename: Rojana
authors.initials: R
authors.lastname: Sukchawalit
authors.affiliation: Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.|Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand.|Center of Excellence on Environmental Health and Toxicology (EHT), Ministry of Education, Bangkok, Thailand.
authors.forename: Skorn
authors.initials: S
authors.lastname: Mongkolsuk
mesh_terms: D016960:Agrobacterium tumefaciens / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D024881:Drug Resistance, Bacterial; D005293:Ferritins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000378:metabolism* / Q000633:toxicity; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D026901:Membrane Transport Proteins; D005293:Ferritins; D007501:Iron