title: Characterization of Bacillus anthracis iron-regulated surface determinant (Isd) proteins containing NEAT domains.
abstract: Three iron-regulated surface determinant (Isd) proteins, containing NEAr Transporter (NEAT) domains (GBAA4789-7), constitute part of an eight-member Bacillus anthracis operon. GBAA4789 (IsdC), previously characterized by others as a haem-binding protein, and two novel Isd proteins characterized in this study, GBAA4788 (IsdJ) and GBAA4787 (IsdK) proteins, can be translated from two alternative overlapping transcriptional units. The three NEAT-containing Isd proteins are shown to be expressed in vivo during B. anthracis infection. Expression in vitro is regulated by iron ions independent of the virulence plasmids pXO1 and pXO2, yet their presence affects the range of response to iron ion concentration. The expression of IsdC, J and K is strongly repressed under high CO(2) tension, conditions that are optimal for B. anthracis toxin and capsule expression, suggesting that these Isd proteins are elements of a B. anthracis'air-regulon'. Deletion mutants of isdC, isdK or the entire isdCJK locus are as virulent and pathogenic to guinea pigs as the fully virulent wild-type Vollum strain. The isdC-deleted mutant is defective in sequestration of haemin, consistent with previous biochemical observations, while the DeltaisdK mutant is defective in haemoglobin uptake. Studies with recombinant IsdK demonstrate specific binding to haemoglobin.
authors.affiliation: Department of Biochemistry and Molecular Genetics, Israel Institute for biological Research, Ness Ziona, Israel. oritg@iibr.gov.il
authors.forename: Orit
authors.initials: O
authors.lastname: Gat
authors.forename: Galia
authors.initials: G
authors.lastname: Zaide
authors.forename: Izhak
authors.initials: I
authors.lastname: Inbar
authors.forename: Haim
authors.initials: H
authors.lastname: Grosfeld
authors.forename: Theodor
authors.initials: T
authors.lastname: Chitlaru
authors.forename: Haim
authors.initials: H
authors.lastname: Levy
authors.forename: Avigdor
authors.initials: A
authors.lastname: Shafferman
mesh_terms: D000818:Animals; D000881:Anthrax / Q000382:microbiology; D001408:Bacillus anthracis / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006168:Guinea Pigs; D006418:Heme / Q000378:metabolism; D006454:Hemoglobins / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D009154:Mutation; D016366:Open Reading Frames; D009876:Operon; D010957:Plasmids; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011817:Rabbits; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D006454:Hemoglobins; D002245:Carbon Dioxide; D006418:Heme; D007501:Iron