title: Three-dimensional structure of two crystal forms of FabR19.9 from a monoclonal anti-arsonate antibody.
abstract: The three-dimensional structure of FabR19.9 from a well-characterized anti-p-azobenzenearsonate monoclonal antibody has been determined by x-ray diffraction techniques in two crystalline forms (I and II) to a resolution of 2.8 and 2.7 A, respectively. Essentially the same tertiary and quaternary structure of the Fab is observed in the two forms. The major difference resides in the intermolecular contacts, which are interpreted to favor an irreversible transition from the metastable form I to the more stable form II. The third complementarity-determining region of the heavy chain (H3) folds back over the combining site and requires rearrangement for hapten binding. This dynamic requirement on H3 is consistent with its mobility in the structure and can explain hapten binding to an otherwise inaccessible antibody combining site.
authors.affiliation: Unite de Recherche Associée 359 Centre National de la Recherche Scientifique, Institut Pasteur, Paris, France.
authors.forename: M B
authors.initials: MB
authors.lastname: Lascombe
authors.forename: P M
authors.initials: PM
authors.lastname: Alzari
authors.forename: R J
authors.initials: RJ
authors.lastname: Poljak
authors.forename: A
authors.initials: A
authors.lastname: Nisonoff
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000648:ultrastructure*; D001666:Binding Sites, Antibody; D003461:Crystallography; D006241:Haptens; D007140:Immunoglobulin Fab Fragments / Q000648:ultrastructure*; D066298:In Vitro Techniques; D051379:Mice; D008958:Models, Molecular; D011487:Protein Conformation; D014961:X-Ray Diffraction; D010132:p-Azobenzenearsonate / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D006241:Haptens; D007140:Immunoglobulin Fab Fragments; D010132:p-Azobenzenearsonate