title: Recognition of a cell-surface oligosaccharide of pathogenic Salmonella by an antibody Fab fragment.
abstract: The 2.05 angstrom (A) resolution crystal structure of a dodecasaccharide-Fab complex revealed an unusual carbohydrate recognition site, defined by aromatic amino acids and a structured water molecule, rather than the carboxylic acid and amide side chains and a structured water molecule, rather than the carboxylic acid and amide side chains that are features of transport and other carbohydrate binding proteins. A trisaccharide epitope of a branched bacterial lipopolysaccharide fills this hydrophobic pocket (8 A deep by 7 A wide) in an entropy-assisted association (association constant = 2.05 x 10(5) liters per mole, enthalpy = -20.5 +/- 1.7 kilojoules per mole, and temperature times entropy = +10.0 +/- 2.9 kilojoules per mole). The requirement for the complementarity of van der Waals surfaces and the requirements of saccharide-saccharide and protein-saccharide hydrogen-bonding networks determine the antigen conformation adopted in the bound state.
authors.affiliation: Biotechnology Research Institute, National Research Council of Canada, Montréal, Québec.
authors.forename: M
authors.initials: M
authors.lastname: Cygler
authors.forename: D R
authors.initials: DR
authors.lastname: Rose
authors.forename: D R
authors.initials: DR
authors.lastname: Bundle
mesh_terms: D000595:Amino Acid Sequence; D000936:Antigen-Antibody Complex; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D000939:Epitopes / Q000737:chemistry; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry / Q000276:immunology*; D007074:Immunoglobulin G / Q000145:classification / Q000276:immunology*; D008070:Lipopolysaccharides / Q000737:chemistry / Q000276:immunology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry / Q000276:immunology*; D011487:Protein Conformation; D012475:Salmonella / Q000276:immunology* / Q000472:pathogenicity
chemical_list: D000936:Antigen-Antibody Complex; D000939:Epitopes; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D008070:Lipopolysaccharides; D009844:Oligosaccharides