Biochemical and immunological properties of lactoferrin binding proteins from Moraxella (Branhamella) catarrhalis

Robert A. Bonnah, Rong Hua Yu, Henry Wong, Anthony B. Schryvers

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


The Neisseriaceae can acquire iron (Fe) from lactoferrin (Lf) using host-Lf receptors on the bacterial surface. The binding proteins that are proposed to constitute the receptor have been identified by isolation with immobilized if. Using CopB-specific monoclonal antibodies and isogenic CopB mutants, we demonstrate that the 84 kDa protein isolated with immobilized human if from Moraxella catarrhalis using low stringency conditions is CopB, an 84 kDa membrane-spanning protein with similarities to other TonB-dependent outer membrane proteins. Affinity isolation of Lf receptors from a variety of M. catarrhalis strains using high stringency conditions revealed a 95 kDa protein migrating slightly faster than LbpA on SDS-PAGE in some strains. Convalescent human antisera from patients infected with M. catarrhalis reacted specifically with this protein, but not LbpA. Proteolysis experiments demonstrated that, unlike LbpA, it was rapidly degraded. The 95 kDa protein, but not LbpA, binds labelled if after SDS-PAGE and electroblotting, suggesting the 95 kDa protein is LbpB, the homologue of TbpB. This protein comigrates with LbpA in most strains, which may explain why it had not been previously identified.

Original languageEnglish (US)
Pages (from-to)89-100
Number of pages12
JournalMicrobial Pathogenesis
Issue number2
StatePublished - Feb 1998
Externally publishedYes


  • Iron
  • Lactoferrin
  • Lactoferrin binding protein
  • Transferrin
  • Transferrin binding protein

ASJC Scopus subject areas

  • Microbiology
  • Infectious Diseases


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