title: His-tag binding by antibody C706 mimics β-amyloid recognition.
abstract: Alzheimer's disease is a progressive neurodegenerative disease characterized by extracellular deposits of β-amyloid (Aβ) plaques. Aggregation of the Aβ(42) peptide leading to plaque formation is believed to play a central role in Alzheimer's disease pathogenesis. Anti-Aβ monoclonal antibodies can reduce amyloid plaques and could possibly be used for immunotherapy. We have developed a monoclonal antibody C706, which recognizes the human Aβ peptide. Here we report the crystal structure of the antibody Fab fragment at 1.7 Å resolution. The structure was determined in two crystal forms, P2(1) and C2. Although the Fab was crystallized in the presence of Aβ(16), no peptide was observed in the crystals. The antigen-binding site is blocked by the hexahistidine tag of another Fab molecule in both crystal forms. The poly-His peptide in an extended conformation occupies a crevice between the light and heavy chains of the variable domain. Two consecutive histidines (His4-His5) stack against tryptophan residues in the central pocket of the antigen-binding surface. In addition, they form hydrogen bonds to the acidic residues at the bottom of the pocket. The mode of his-tag binding by C706 resembles the Aβ recognition by antibodies PFA1 and WO2. All three antibodies recognize the same immunodominant B-cell epitope of Aβ. By similarity, residues Phe-Arg-His of Aβ would be a major portion of the C706 epitope.
authors.affiliation: Centocor R&D, 145 King of Prussia Road, Radnor, PA 19087, USA. ateplyak@its.jnj.com
authors.forename: Alexey
authors.initials: A
authors.lastname: Teplyakov
authors.forename: Galina
authors.initials: G
authors.lastname: Obmolova
authors.forename: Gabriela
authors.initials: G
authors.lastname: Canziani
authors.forename: Yonghong
authors.initials: Y
authors.lastname: Zhao
authors.forename: Lester
authors.initials: L
authors.lastname: Gutshall
authors.forename: Sonia S
authors.initials: SS
authors.lastname: Jung
authors.forename: Gary L
authors.initials: GL
authors.lastname: Gilliland
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000378:metabolism*; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
chemical_list: D016229:Amyloid beta-Peptides; D000911:Antibodies, Monoclonal