title: The IgD CH1 region contains the binding site for the human respiratory pathogen Moraxella catarrhalis IgD-binding protein MID.
abstract: The Moraxella catarrhalis IgD-binding protein (MID) has a unique specificity for human IgD, and the sequence with maximal IgD binding is located within the amino acids MID962-1200. In the present paper, we examined the MID binding site on IgD using a series of recombinant Ig. Full-length IgD, IgD F(ab')2, and an IgD F(ab') C290R mutant lacking the inter-heavy-chain cysteine 290 were manufactured. Furthermore, a series of IgD/IgG chimeras were constructed. ELISA, dot blot and flow cytometry were used to study the binding of purified Ig to native MID, recombinant MID962-1200 or to Moraxella with or without MID. MID962-1200 bound both the IgD F(ab')2 and F(ab') C290R, indicating that the binding occurred independently of antibody structure. When amino acids 157-224 of the IgD CH1 region were substituted with IgG sequences, binding by M. catarrhalis or recombinant MID962-1200 was abolished. Subsequent smaller substitutions of IgD CH1 157-224 with IgG sequences led us to conclude that IgD CH1 amino acids 198-206 were crucial for the interaction between MID and IgD.
authors.affiliation: Medical Microbiology, Department of Laboratory Medicine, Lund University, Malmö University Hospital, Malmö, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Samuelsson
authors.forename: Johan
authors.initials: J
authors.lastname: Jendholm
authors.forename: Stefan
authors.initials: S
authors.lastname: Amisten
authors.forename: Sherie L
authors.initials: SL
authors.lastname: Morrison
authors.forename: Arne
authors.initials: A
authors.lastname: Forsgren
authors.forename: Kristian
authors.initials: K
authors.lastname: Riesbeck
mesh_terms: D018829:Adhesins, Bacterial / Q000276:immunology* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001666:Binding Sites, Antibody / Q000276:immunology*; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D007072:Immunoglobulin D / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D007143:Immunoglobulin Heavy Chains / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D008969:Molecular Sequence Data; D001936:Moraxella catarrhalis / Q000276:immunology; D011485:Protein Binding / Q000276:immunology; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology
chemical_list: D018829:Adhesins, Bacterial; C439616:IgD-binding protein MID, Moraxella catarrhalis; D007072:Immunoglobulin D; D007143:Immunoglobulin Heavy Chains; D011994:Recombinant Proteins