title: Covalent structural changes in unfolded GroES that lead to amyloid fibril formation detected by NMR: insight into intrinsically disordered proteins.
abstract: Co-chaperonin GroES from Escherichia coli works with chaperonin GroEL to mediate the folding reactions of various proteins. However, under specific conditions, i.e. the completely disordered state in guanidine hydrochloride, this molecular chaperone forms amyloid fibrils similar to those observed in various neurodegenerative diseases. Thus, this is a good model system to understand the amyloid fibril formation mechanism of intrinsically disordered proteins. Here, we identified a critical intermediate of GroES in the early stages of this fibril formation using NMR and mass spectroscopy measurements. A covalent rearrangement of the polypeptide bond at Asn(45)-Gly(46) and/or Asn(51)-Gly(52) that eventually yield β-aspartic acids via deamidation of asparagine was observed to precede fibril formation. Mutation of these asparagines to alanines resulted in delayed nucleus formation. Our results indicate that peptide bond rearrangement at Asn-Gly enhances the formation of GroES amyloid fibrils. The finding provides a novel insight into the structural process of amyloid fibril formation from a disordered state, which may be applicable to intrinsically disordered proteins in general.
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, Tottori 680-8552, Japan.
authors.forename: Hisanori
authors.initials: H
authors.lastname: Iwasa
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Meshitsuka
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Hongo
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Mizobata
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kawata
mesh_terms: D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry*; D001216:Asparagine / Q000737:chemistry; D001224:Aspartic Acid / Q000737:chemistry; D018835:Chaperonin 10 / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D019791:Guanidine / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D013058:Mass Spectrometry / Q000379:methods; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D000682:Amyloid; D018835:Chaperonin 10; D010455:Peptides; D001224:Aspartic Acid; D001216:Asparagine; D019791:Guanidine; D000409:Alanine