title: Groove-type recognition of chlamydiaceae-specific lipopolysaccharide antigen by a family of antibodies possessing an unusual variable heavy chain N-linked glycan.
abstract: The structure of the antigen binding fragment of mAb S25-26, determined to 1.95 Å resolution in complex with the Chlamydiaceae family-specific trisaccharide antigen Kdo(2→8)Kdo(2→4)Kdo (Kdo = 3-deoxy-α-d-manno-oct-2-ulopyranosonic acid), displays a germ-line-coded paratope that differs significantly from previously characterized Chlamydiaceae-specific mAbs despite being raised against the identical immunogen. Unlike the terminal Kdo recognition pocket that promotes cross-reactivity in S25-2-type antibodies, S25-26 and the closely related S25-23 utilize a groove composed of germ-line residues to recognize the entire trisaccharide antigen and so confer strict specificity. Interest in S25-23 was sparked by its rare high μm affinity and strict specificity for the family-specific trisaccharide antigen; however, only the related antibody S25-26 proved amenable to crystallization. The structures of three unliganded forms of S25-26 have a labile complementary-determining region H3 adjacent to significant glycosylation of the variable heavy chain on asparagine 85 in Framework Region 3. Analysis of the glycan reveals a heterogeneous mixture with a common root structure that contains an unusually high number of terminal αGal-Gal moieties. One of the few reported structures of glycosylated mAbs containing these epitopes is the therapeutic antibody Cetuximab; however, unlike Cetuximab, one of the unliganded structures in S25-26 shows significant order in the glycan with appropriate electron density for nine residues. The elucidation of the three-dimensional structure of an αGal-containing N-linked glycan on a mAb variable heavy chain has potential clinical interest, as it has been implicated in allergic response in patients receiving therapeutic antibodies.
authors.affiliation: From the Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8P 3P6, Canada.
authors.forename: Omid
authors.initials: O
authors.lastname: Haji-Ghassemi
authors.affiliation: Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 22, Borstel D-23845, Germany, sml@fz-borstel.de.
authors.forename: Sven
authors.initials: S
authors.lastname: Müller-Loennies
authors.affiliation: GlycoScience Group, the National Institute for Bioprocessing Research and Training (NIBRT), Mount Merrion, Blackrock, Dublin 4, Ireland.
authors.forename: Radka
authors.initials: R
authors.lastname: Saldova
authors.affiliation: GlycoScience Group, the National Institute for Bioprocessing Research and Training (NIBRT), Mount Merrion, Blackrock, Dublin 4, Ireland.
authors.forename: Mohankumar
authors.initials: M
authors.lastname: Muniyappa
authors.affiliation: Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 22, Borstel D-23845, Germany.
authors.forename: Lore
authors.initials: L
authors.lastname: Brade
authors.affiliation: GlycoScience Group, the National Institute for Bioprocessing Research and Training (NIBRT), Mount Merrion, Blackrock, Dublin 4, Ireland.
authors.forename: Pauline M
authors.initials: PM
authors.lastname: Rudd
authors.affiliation: Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom.
authors.forename: David J
authors.initials: DJ
authors.lastname: Harvey
authors.affiliation: University of Natural Resources and Life Sciences, Vienna, Austria, and.
authors.forename: Paul
authors.initials: P
authors.lastname: Kosma
authors.affiliation: Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 22, Borstel D-23845, Germany.
authors.forename: Helmut
authors.initials: H
authors.lastname: Brade
authors.affiliation: From the Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8P 3P6, Canada, svevans@uvic.ca.
authors.forename: Stephen V
authors.initials: SV
authors.lastname: Evans
mesh_terms: D000595:Amino Acid Sequence; D000907:Antibodies, Bacterial / Q000737:chemistry / Q000276:immunology; D000915:Antibody Affinity; D001666:Binding Sites, Antibody; D002689:Chlamydia / Q000737:chemistry / Q000276:immunology*; D007143:Immunoglobulin Heavy Chains / Q000737:chemistry* / Q000276:immunology; D007135:Immunoglobulin Variable Region / Q000737:chemistry* / Q000276:immunology; D008070:Lipopolysaccharides / Q000737:chemistry* / Q000276:immunology; D062105:Molecular Docking Simulation; D008969:Molecular Sequence Data
chemical_list: D000907:Antibodies, Bacterial; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D008070:Lipopolysaccharides
keywords: Antibodies; Antigen; Carbohydrate Complex; Glycosylation; X-ray Crystallography