title: Investigation of a peptide responsible for amyloid fibril formation of beta 2-microglobulin by achromobacter protease I.
abstract: To obtain insight into the mechanism of amyloid fibril formation from beta(2)-microglobulin (beta2-m), we prepared a series of peptide fragments using a lysine-specific protease from Achromobacter lyticus and examined their ability to form amyloid fibrils at pH 2.5. Among the nine peptides prepared by the digestion, the peptide Ser(20)-Lys(41) (K3) spontaneously formed amyloid fibrils, confirmed by thioflavin T binding and electron microscopy. The fibrils composed of K3 peptide induced fibril formation of intact beta2-m with a lag phase, distinct from the extension reaction without a lag phase observed for intact beta2-m seeds. Fibril formation of K3 peptide with intact beta2-m seeds also exhibited a lag phase. On the other hand, the extension reaction of K3 peptide with the K3 seeds occurred without a lag phase. At neutral pH, the fibrils composed of either intact beta2-m or K3 peptide spontaneously depolymerized. Intriguingly, the depolymerization of K3 fibrils was faster than that of intact beta2-m fibrils. These results indicated that, although K3 peptide can form fibrils by itself more readily than intact beta2-m, the K3 fibrils are less stable than the intact beta2-m fibrils, suggesting a close relation between the free energy barrier of amyloid fibril formation and its stability.
authors.affiliation: Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan.
authors.forename: Gennady V
authors.initials: GV
authors.lastname: Kozhukh
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Hagihara
authors.forename: Toru
authors.initials: T
authors.lastname: Kawakami
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Hasegawa
authors.forename: Hironobu
authors.initials: H
authors.lastname: Naiki
authors.forename: Yuji
authors.initials: Y
authors.lastname: Goto
mesh_terms: D000595:Amino Acid Sequence; D000682:Amyloid / Q000378:metabolism* / Q000648:ultrastructure; D052160:Benzothiazoles; D002942:Circular Dichroism; D005456:Fluorescent Dyes / Q000378:metabolism; D006801:Humans; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism*; D011108:Polymers / Q000737:chemistry; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism*; D013844:Thiazoles / Q000378:metabolism; D013997:Time Factors; D001613:beta 2-Microglobulin / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D000682:Amyloid; D052160:Benzothiazoles; D005456:Fluorescent Dyes; D010446:Peptide Fragments; D011108:Polymers; D011994:Recombinant Proteins; D013844:Thiazoles; D001613:beta 2-Microglobulin; C009462:thioflavin T; D012697:Serine Endopeptidases; C036813:lysyl endopeptidase