title: Complementarity-determining region 2 is implicated in the binding of staphylococcal protein A to human immunoglobulin VHIII variable regions.
abstract: Staphylococcal protein A (SPA) has two distinct binding sites on human immunoglobulins. In addition to binding to the Fc region of most IgG molecules, an "alternative" binding site has been localized to the Fab region of human immunoglobulins encoded by heavy chain variable gene segments belonging to the VHIII family. Comparison of amino acid sequences of closely related SPA-binding and -non-binding proteins suggested that VHIII-specific residues in the second complementarity-determining region (CDR2) were likely responsible for SPA binding activity. Site-directed mutagenesis of a single amino acid residue in CDR2 converted an IgM rheumatoid factor which did not bind SPA to an SPA binder. These findings, therefore, locate a critical site involved in SPA binding to the CDR2 of human immunoglobulins encoded by VHIII family gene segments.
authors.affiliation: Institute of Immunology and Rheumatology, Oslo, Norway.
authors.forename: I
authors.initials: I
authors.lastname: Randen
authors.forename: K N
authors.initials: KN
authors.lastname: Potter
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: K M
authors.initials: KM
authors.lastname: Thompson
authors.forename: V
authors.initials: V
authors.lastname: Pascual
authors.forename: O
authors.initials: O
authors.lastname: Førre
authors.forename: J B
authors.initials: JB
authors.lastname: Natvig
authors.forename: J D
authors.initials: JD
authors.lastname: Capra
mesh_terms: D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D005803:Genes, Immunoglobulin; D006801:Humans; D007074:Immunoglobulin G / Q000235:genetics / Q000378:metabolism; D007075:Immunoglobulin M / Q000235:genetics / Q000378:metabolism; D007135:Immunoglobulin Variable Region / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D013205:Staphylococcal Protein A / Q000276:immunology* / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D007135:Immunoglobulin Variable Region; D013205:Staphylococcal Protein A; D004247:DNA