TY - JOUR
T1 - Biochemical and immunological properties of lactoferrin binding proteins from Moraxella (Branhamella) catarrhalis
AU - Bonnah, Robert A.
AU - Yu, Rong Hua
AU - Wong, Henry
AU - Schryvers, Anthony B.
PY - 1998/2
Y1 - 1998/2
N2 - 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.
AB - 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.
KW - Iron
KW - Lactoferrin
KW - Lactoferrin binding protein
KW - Transferrin
KW - Transferrin binding protein
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U2 - 10.1006/mpat.1997.0173
DO - 10.1006/mpat.1997.0173
M3 - Article
C2 - 9480791
AN - SCOPUS:0031933035
SN - 0882-4010
VL - 24
SP - 89
EP - 100
JO - Microbial Pathogenesis
JF - Microbial Pathogenesis
IS - 2
ER -