title: Structures of Abeta-related peptide--monoclonal antibody complexes.
abstract: Passive immunotherapy (PI) is being explored as a potential therapeutic against Alzheimer's disease. The most promising antibodies (Abs) used in PI target the EFRH motif of the Abeta N-terminus. The monoclonal anti-Abeta Ab PFA1 recognizes the EFRH epitope of Abeta. PFA1 has a high affinity for Abeta fibrils and protofibrils (0.1 nM), as well as good affinity for Abeta monomers (20 nM). However, PFA1 binds the toxic N-terminally modified pyroglutamate peptide pyro-Glu3-Abeta with a 77-fold loss in affinity compared to the WT Abeta(1-8). Furthermore, our earlier work illustrated PFA1's potential for cross-reactivity. The receptor tyrosine kinase Ror2, which plays a role in skeletal and bone formation, possesses the EFRH sequence. PFA1 Fab binds the Ror2(518-525) peptide sequence REEFRHEA with a 3-fold enhancement over WT Abeta(1-8). In this work, the crystal structures of the hybridoma-derived PFA1 Fab in complex with pyro-Glu3-Abeta peptide and with a cross-reacting peptide from Ror2 have been determined at resolutions of 1.95 and 2.7 A, respectively. As with wild-type Abeta, these peptides bind to the Fab via a combination of charge- and shape-complementarity, hydrogen-bonding, and hydrophobic interactions. Comparison of the structures of the four peptides Abeta(1-8), Grip1, pyro-Glu3-Abeta(3-8), and Ror2 in complex with PFA1 shows that the greatest conformational flexibility occurs at residues 2 to 3 and 8 of the peptide. These structures provide a molecular basis of the specificity tolerance of PFA1 and its ability to recognize Abeta N-terminal heterogeneity. The structures provide clues to improving mAb specificity and affinity for pyroglutamate Abeta.
authors.affiliation: Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Gardberg
authors.forename: Lezlee
authors.initials: L
authors.lastname: Dice
authors.forename: Kathleen
authors.initials: K
authors.lastname: Pridgen
authors.forename: Jan
authors.initials: J
authors.lastname: Ko
authors.forename: Paul
authors.initials: P
authors.lastname: Patterson
authors.forename: Susan
authors.initials: S
authors.lastname: Ou
authors.forename: Ronald
authors.initials: R
authors.lastname: Wetzel
authors.forename: Chris
authors.initials: C
authors.lastname: Dealwis
mesh_terms: D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000276:immunology* / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D000939:Epitopes / Q000737:chemistry / Q000378:metabolism; D006860:Hydrogen Bonding; D007116:Immunization, Passive; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation
chemical_list: D016229:Amyloid beta-Peptides; D000911:Antibodies, Monoclonal; D000939:Epitopes; D010455:Peptides