title: Iron response regulator protein IrrB in Magnetospirillum gryphiswaldense MSR-1 helps control the iron/oxygen balance, oxidative stress tolerance, and magnetosome formation.
abstract: Magnetotactic bacteria are capable of forming nanosized, membrane-enclosed magnetosomes under iron-rich and oxygen-limited conditions. The complete genomic sequence of Magnetospirillum gryphiswaldense strain MSR-1 has been analyzed and found to contain five fur homologue genes whose protein products are predicted to be involved in iron homeostasis and the response to oxidative stress. Of these, only the MGMSRv2_3149 gene (irrB) was significantly downregulated under high-iron and low-oxygen conditions, during the transition of cell growth from the logarithmic to the stationary phase. The encoded protein, IrrB, containing the conserved HHH motif, was identified as an iron response regulator (Irr) protein belonging to the Fur superfamily. To investigate the function of IrrB, we constructed an irrB deletion mutant (ΔirrB). The levels of cell growth and magnetosome formation were lower in the ΔirrB strain than in the wild type (WT) under both high-iron and low-iron conditions. The ΔirrB strain also showed lower levels of iron uptake and H2O2 tolerance than the WT. Quantitative real-time reverse transcription-PCR analysis indicated that the irrB mutation reduced the expression of numerous genes involved in iron transport, iron storage, heme biosynthesis, and Fe-S cluster assembly. Transcription studies of the other fur homologue genes in the ΔirrB strain indicated complementary functions of the Fur proteins in MSR-1. IrrB appears to be directly responsible for iron metabolism and homeostasis and to be indirectly involved in magnetosome formation. We propose two IrrB-regulated networks (under high- and low-iron conditions) in MSR-1 cells that control the balance of iron and oxygen metabolism and account for the coexistence of five Fur homologues.
authors.affiliation: State Key Laboratories for Agro-Biotechnology, China Agricultural University, Beijing, People's Republic of China College of Agriculture and Biotechnology, China Agricultural University, Beijing, People's Republic of China France-China Biomineralization and Nanostructure Laboratory, Beijing, People's Republic of China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Wang
authors.affiliation: State Key Laboratories for Agro-Biotechnology, China Agricultural University, Beijing, People's Republic of China France-China Biomineralization and Nanostructure Laboratory, Beijing, People's Republic of China.
authors.forename: Meiwen
authors.initials: M
authors.lastname: Wang
authors.affiliation: State Key Laboratories for Agro-Biotechnology, China Agricultural University, Beijing, People's Republic of China France-China Biomineralization and Nanostructure Laboratory, Beijing, People's Republic of China.
authors.forename: Xu
authors.initials: X
authors.lastname: Wang
authors.affiliation: State Key Laboratories for Agro-Biotechnology, China Agricultural University, Beijing, People's Republic of China France-China Biomineralization and Nanostructure Laboratory, Beijing, People's Republic of China.
authors.forename: Guohua
authors.initials: G
authors.lastname: Guan
authors.affiliation: State Key Laboratories for Agro-Biotechnology, China Agricultural University, Beijing, People's Republic of China France-China Biomineralization and Nanostructure Laboratory, Beijing, People's Republic of China yingli528@vip.sina.com.
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Laboratories for Agro-Biotechnology, China Agricultural University, Beijing, People's Republic of China College of Agriculture and Biotechnology, China Agricultural University, Beijing, People's Republic of China.
authors.forename: Youliang
authors.initials: Y
authors.lastname: Peng
authors.affiliation: State Key Laboratories for Agro-Biotechnology, China Agricultural University, Beijing, People's Republic of China France-China Biomineralization and Nanostructure Laboratory, Beijing, People's Republic of China.
authors.forename: Jilun
authors.initials: J
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D015536:Down-Regulation; D052203:Ferrosoferric Oxide / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D035925:Iron-Regulatory Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D055944:Magnetosomes / Q000378:metabolism*; D042201:Magnetospirillum / Q000235:genetics* / Q000378:metabolism; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism*; D016415:Sequence Alignment; D017384:Sequence Deletion
chemical_list: D035925:Iron-Regulatory Proteins; D007501:Iron; D010100:Oxygen; D052203:Ferrosoferric Oxide