title: Structure of amyloid beta fragments in aqueous environments.
abstract: Conformational studies on amyloid beta peptide (Abeta) in aqueous solution are complicated by its tendency to aggregate. In this study, we determined the atomic-level structure of Abeta(28-42) in an aqueous environment. We fused fragments of Abeta, residues 10-24 (Abeta(10-24)) or 28-42 (Abeta(28-42)), to three positions in the C-terminal region of ribonuclease HII from a hyperthermophile, Thermococcus kodakaraensis (Tk-RNase HII). We then examined the structural properties in an aqueous environment. The host protein, Tk-RNase HII, is highly stable and the C-terminal region has relatively little interaction with other parts. CD spectroscopy and thermal denaturation experiments demonstrated that the guest amyloidogenic sequences did not affect the overall structure of the Tk-RNase HII. Crystal structure analysis of Tk-RNase HII(1-197)-Abeta(28-42) revealed that Abeta(28-42) forms a beta conformation, whereas the original structure in Tk-RNase HII(1-213) was alpha helix, suggesting beta-structure formation of Abeta(28-42) within full-length Abeta in aqueous solution. Abeta(28-42) enhanced aggregation of the host protein more strongly than Abeta(10-24). These results and other reports suggest that after proteolytic cleavage, the C-terminal region of Abeta adopts a beta conformation in an aqueous environment and induces aggregation, and that the central region of Abeta plays a critical role in fibril formation. This study also indicates that this fusion technique is useful for obtaining structural information with atomic resolution for amyloidogenic peptides in aqueous environments.
authors.affiliation: Department of Material and Life Science, Osaka University, Suita, Japan. ktakano@mls.eng.osaka-u.ac.jp
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Takano
authors.forename: Shuji
authors.initials: S
authors.lastname: Endo
authors.forename: Atsushi
authors.initials: A
authors.lastname: Mukaiyama
authors.forename: Hyongi
authors.initials: H
authors.lastname: Chon
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Matsumura
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Koga
authors.forename: Shigenori
authors.initials: S
authors.lastname: Kanaya
mesh_terms: D000595:Amino Acid Sequence; D000682:Amyloid; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000494:pharmacology; D052160:Benzothiazoles; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D004795:Enzyme Stability; D024022:Fibrillar Collagens / Q000502:physiology; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D010446:Peptide Fragments / Q000737:chemistry*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification; D016914:Ribonuclease H / Q000737:chemistry / Q000302:isolation & purification; D019712:Thermococcus / Q000737:chemistry / Q000201:enzymology; D013844:Thiazoles / Q000737:chemistry / Q000378:metabolism; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D000682:Amyloid; D016229:Amyloid beta-Peptides; D052160:Benzothiazoles; D024022:Fibrillar Collagens; D010446:Peptide Fragments; D011994:Recombinant Proteins; D013844:Thiazoles; D014867:Water; C009462:thioflavin T; C091139:ribonuclease HII; D016914:Ribonuclease H