title: Molecular cloning of haemoglobin-binding protein HgbA in the outer membrane of Actinobacillus pleuropneumoniae.
abstract: From the porcine pathogen Actinobacillus pleuropneumoniae cultivated in iron-deficient or haem-deficient media, haemoglobin (Hb)-agarose affinity purification was exploited to isolate an outer-membrane protein of approximately 105 kDa, designated HgbA. Internal peptide sequences of purified HgbA were used to design oligonucleotide primers for PCR amplification, yielding amplicons that showed partial sequences with homology to hgbA of Pasteurella multocida. Upon screening two genomic libraries of A. pleuropneumoniae serotype 1 strain 4074, positive clones were assembled into an ORF of 2838 bp. HgbA (946 aa) includes a signal peptide of 23 aa and the deduced HgbA sequence (104 890 Da) also demonstrated a possible Ton box. The promoter region of hgbA from A. pleuropneumoniae serotype 1 showed consensus for -35 and -10 sequences and a putative Fur-binding site. RT-PCR confirmed that hgbA of A. pleuropneumoniae is upregulated in response to diminished levels of iron in the culture medium. While an internally deleted hgbA mutant was unable to use pig Hb as sole source of iron for growth, flow cytometry confirmed its Hb binding; the internally deleted sequences may not be required for Hb binding, but appear necessary for the iron supply from Hb. HgbA is required for growth of A. pleuropneumoniae in the presence of Hb as sole iron source.
authors.affiliation: Department of Microbiology and Immunology, McGill University, 3775 University Street, Montreal, QC, Canada H3A 2B4.
authors.forename: Ramakrishnan
authors.initials: R
authors.lastname: Srikumar
authors.affiliation: Groupe de Recherche sur les Maladies Infectieuses du Porc, Département de Pathologie et Microbiologie, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, QC, Canada J2S 7C6.
authors.forename: Leonie G
authors.initials: LG
authors.lastname: Mikael
authors.affiliation: Department of Microbiology and Immunology, McGill University, 3775 University Street, Montreal, QC, Canada H3A 2B4.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Pawelek
authors.affiliation: Department of Microbiology and Immunology, McGill University, 3775 University Street, Montreal, QC, Canada H3A 2B4.
authors.forename: Ali
authors.initials: A
authors.lastname: Khamessan
authors.affiliation: MDS Pharma Services, St Laurent, QC, Canada H4R 2N6.
authors.forename: Bernard F
authors.initials: BF
authors.lastname: Gibbs
authors.affiliation: Groupe de Recherche sur les Maladies Infectieuses du Porc, Département de Pathologie et Microbiologie, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, QC, Canada J2S 7C6.
authors.forename: Mario
authors.initials: M
authors.lastname: Jacques
authors.affiliation: Department of Microbiology and Immunology, McGill University, 3775 University Street, Montreal, QC, Canada H3A 2B4.
authors.forename: James W
authors.initials: JW
authors.lastname: Coulton
mesh_terms: D016977:Actinobacillus pleuropneumoniae / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins; D001483:Base Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D006454:Hemoglobins / Q000378:metabolism*; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D006454:Hemoglobins; D011994:Recombinant Proteins; C017206:hemoglobin-binding protein, bacteria