title: Lactoferrin interaction with Actinobacillus actinomycetemcomitans.
abstract: The interaction of lactoferrin with Actinobacillus actinomycetemcomitans was examined in a 125I-labeled protein binding assay. The binding of human and bovine lactoferrins reached maximum within 1 h. Lactoferrin binding to the bacterium was pH-dependent and reversible. Scatchard analysis indicated the existence of two different types of binding sites on the bacterium, one with a high affinity constant k alpha approximately 8.8 x 10(-7) M) and the other with a low one (k alpha approximately 1.8 x 10(-6) M). Bacteria in the exponential phase of growth showed higher binding than cells in the stationary phase. Bacteria grown in medium containing serum and/or lysed erythrocytes bound lactoferrin to a lesser extent. Heat-inactivated serum, lysed erythrocytes and other proteins such as mucin and laminin inhibited lactoferrin binding to A. actinomycetemcomitans in a competitive binding assay. Sodium dodecyl sulfate polyacrylamide-gel electrophoresis and Western blot analysis of the cell envelope as well as the outer membrane of A. actinomycetemcomitans revealed lactoferrin-reactive protein bands at 29 kDa and 16.5 kDa. The 29-kDa band displayed a heat-modifiable lactoferrin-reactive form with a molecular weight of 34 kDa. Neither proteinase K-treated cell envelope nor lipopolysaccharide of this bacterium showed reactivity with lactoferrin. These data suggests a specific interaction of lactoferrin with outer membrane proteins of A. actinomycetemcomitans.
authors.affiliation: Department of Medical Microbiology, Malmö General Hospital, Lund University, Sweden.
authors.forename: K R
authors.initials: KR
authors.lastname: Alugupalli
authors.forename: S
authors.initials: S
authors.lastname: Kalfas
authors.forename: S
authors.initials: S
authors.lastname: Edwardsson
authors.forename: A S
authors.initials: AS
authors.lastname: Naidu
mesh_terms: D016976:Aggregatibacter actinomycetemcomitans / Q000378:metabolism*; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001667:Binding, Competitive; D002417:Cattle; D004591:Electrophoresis, Polyacrylamide Gel; D005340:Fibrinogen / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism; D006736:Horses; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007781:Lactoferrin / Q000378:metabolism*; D007797:Laminin / Q000378:metabolism; D009077:Mucins / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology
chemical_list: D001425:Bacterial Outer Membrane Proteins; D005353:Fibronectins; D007797:Laminin; D009077:Mucins; D005340:Fibrinogen; D007781:Lactoferrin