title: Aggregation and neurotoxicity of mutant amyloid beta (A beta) peptides with proline replacement: importance of turn formation at positions 22 and 23.
abstract: Aggregation of the amyloid beta peptides (A beta 1-42 and A beta 1-40) plays a pivotal role in pathogenesis of Alzheimer's disease. Although it is widely accepted that the aggregates of A betas mainly consist of beta-sheet structure, the precise aggregation mechanism remains unclear. To identify amino acid residues that are important for the beta-sheet formation, a series of proline-substituted mutants of A beta 1-42 peptides at positions 19-26 was synthesized in a highly pure form and their aggregation ability and neurotoxicity on PC12 cells were investigated. All proline-substituted A beta 1-42 mutants except for 22P- and 23P-A beta 1-42 were hard to aggregate and showed weaker cytotoxicity than wild-type A beta 1-42, suggesting that the residues at positions 19-21 and 24-26 are important for the beta-sheet formation. In contrast, 22P-A beta 1-42 extensively aggregated with stronger cytotoxicity than wild-type A beta 1-42. Since proline has a propensity for beta-turn structure as a Pro-X corner, these data implicate that beta-turn formation at positions 22 and 23 plays a crucial role in the aggregation and neurotoxicity of A beta peptides.
authors.affiliation: Laboratory of Organic Chemistry in Life Science, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Morimoto
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Irie
authors.forename: Kazuma
authors.initials: K
authors.lastname: Murakami
authors.forename: Hajime
authors.initials: H
authors.lastname: Ohigashi
authors.forename: Mayumi
authors.initials: M
authors.lastname: Shindo
authors.forename: Masaya
authors.initials: M
authors.lastname: Nagao
authors.forename: Takahiko
authors.initials: T
authors.lastname: Shimizu
authors.forename: Takuji
authors.initials: T
authors.lastname: Shirasawa
mesh_terms: D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D008969:Molecular Sequence Data; D016716:PC12 Cells; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D011392:Proline / Q000737:chemistry*; D017433:Protein Structure, Secondary; D051381:Rats; D017386:Sequence Homology, Amino Acid
chemical_list: D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42); D011392:Proline