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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: All Haemophilus influenzae strains have an absolute requirement for exogenously supplied haem for aerobic growth. A majority of strains of H. influenzae type b (Hib) produce a 100 kDa protein which binds haem: haemopexin complexes. This 100 kDa haem:haemopexin binding protein, designated HxuA, was originally detected on the Hib cell surface. Monoclonal antibody (mAb)-based analyses revealed that the HxuA protein was also present in soluble form in Hib culture supernatants. This soluble HxuA protein exhibited haem:haemopexin-binding activity in a direct binding assay. Nucleotide sequence analysis of the hxuA gene from Hib strain DL42, together with N-terminal amino acid analysis of HxuA protein purified from Hib culture supernatant, revealed that this protein was synthesized as a 101 kDa precursor with a leader peptide that was removed to yield a 99kDa protein. Southern blot analysis of chromosomal DNA from four Hib and four non-typeable H. influenzae (NTHI) strains detected the presence of a single band in each strain that hybridized a Hib hxuA gene probe. Subsequent analysis of these NTHI strains showed that all four strains released into culture supernatant a haem:haemopexin-binding protein that migrated in SDS-PAGE at a rate similar or identical to that of the Hib HxuA protein. A Hib hxuA mutant was used to screen an NTHI genomic DNA library and an NTHI gene was cloned that complemented the mutation in this Hib strain. Nucleotide sequence analysis of this NTHI gene revealed that it encoded a protein with 87% identity to the Hib HxuA protein. The expression of HxuA by both Hib and NTHI strains indicates that this particular haem acquisition system is conserved among H. influenzae strains.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: To elucidate potential vaccine antigens, Moraxella catarrhalis outer membrane proteins (OMPs) were studied. We have previously shown an OMP to be a target for human IgG and have now further characterised this OMP which appears to have a molecular mass of 84 kDa and to be distinct from the 81-kDa OMP, CopB. Human transferrin was shown to bind the 84-kDa OMP alone. N-terminal sequencing of this OMP and purified M. catarrhalis transferrin binding protein B (TbpB) revealed homology both with each other and with the TbpB of Haemophilus influenzae and Neisseria meningitidis. Adsorption of human anti-serum with purified TbpB from two M. catarrhalis strains abolished or reduced binding of IgG to the 84-kDa OMP from three M. catarrhalis isolates. IgG binding to CopB was unaffected. It is clear that the 84-kDa OMP is distinct from CopB and is a likely homologue of TbpB.
    Type of Medium: Electronic Resource
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