title: Crystal structure of the liganded anti-gibberellin A(4) antibody 4-B8(8)/E9 Fab fragment.
abstract: Gibberellins, a class of plant hormones, consist of more than 120 members. Only a few of them are recognized by a receptor that remains unknown. The haptenic mouse monoclonal antibody, 4-B8(8)/E9, was generated against gibberellin A(4) (GA(4)) to recognize biologically active GA selectivity, and we attempted to confirm the binding properties between the antibody and GA(4). We carried out an X-ray crystallographic analysis of the 4-B8(8)/E9 Fab fragment complexed with GA(4) at a 2.8 A resolution by using the molecular replacement method. The crystal structure of the Fab fragment showed the typical immunoglobulin fold of the beta-barrel structure which is the common motif of all antibodies. A small hapten-combining site was made up of three heavy chain CDR loops. On the other hand, CDRs of the light chain did not interact directly with GA(4). The C/D rings of the GA(4) molecule were in van der Waals contact mainly with the aromatic side chain of Tyr100AH and Phe100BH of CDR-H3. The 3 beta-hydroxyl and 6 beta-carboxyl groups were, respectively, hydrogen-bonded to the main chain of Ala33H and to the Thr53H heavy chain.
authors.affiliation: Department of Applied Biological Chemistry, Division of Agriculture and Agricultural Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. tks@pgr1.ch.a.u-tokyo.ac.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Murata
authors.forename: Shinya
authors.initials: S
authors.lastname: Fushinobu
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Nakajima
authors.forename: Osamu
authors.initials: O
authors.lastname: Asami
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sassa
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Wakagi
authors.forename: Isomaro
authors.initials: I
authors.lastname: Yamaguchi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry; D001666:Binding Sites, Antibody; D018360:Crystallography, X-Ray; D019281:Dimerization; D005875:Gibberellins / Q000276:immunology*; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry*; D008024:Ligands; D051379:Mice; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data
chemical_list: D000911:Antibodies, Monoclonal; D005875:Gibberellins; D007140:Immunoglobulin Fab Fragments; D008024:Ligands