title: Early stages of amyloid fibril formation studied by liquid-state NMR: the peptide hormone glucagon.
abstract: The 29-residue peptide hormone glucagon forms amyloid fibrils within a few hours at low pH. In this study, we use glucagon as a model system to investigate fibril formation by liquid-state (1)H-NMR spectroscopy One-dimensional, correlation, and diffusion experiments monitoring the fibril formation process provide insight into the early stages of the pathway on which the molecules aggregate to fibrils. In conjunction with these techniques, exchange experiments give information about the end-state conformation. Within the limits of detection, there are no signs of larger oligomeric intermediates in the course of the fibril formation process. Kinetic information is extracted from the time course of the residual free glucagon signal decay. This suggests that glucagon amyloids form by a nucleated growth mechanism in which trimers (rather than monomers) of glucagon interact directly with the growing fibrils rather than with each other. The results of proton/deuterium exchange experiments on mature fibrils with subsequent dissolution show that the N-terminal of glucagon is the least amenable to exchange, which indicates that this part is strongly involved in the intermolecular bonds of the fibrils.
authors.affiliation: Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO), University of Aarhus, Denmark.
authors.forename: Anna Sigrid Pii
authors.initials: AS
authors.lastname: Svane
authors.forename: Kasper
authors.initials: K
authors.lastname: Jahn
authors.forename: Taru
authors.initials: T
authors.lastname: Deva
authors.forename: Anders
authors.initials: A
authors.lastname: Malmendal
authors.forename: Daniel Erik
authors.initials: DE
authors.lastname: Otzen
authors.forename: Jens
authors.initials: J
authors.lastname: Dittmer
authors.forename: Niels Chr
authors.initials: NC
authors.lastname: Nielsen
mesh_terms: D000682:Amyloid / Q000737:chemistry* / Q000648:ultrastructure*; D003198:Computer Simulation; D003460:Crystallization / Q000379:methods*; D005934:Glucagon / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D044367:Phase Transition; D011487:Protein Conformation; D012996:Solutions
chemical_list: D000682:Amyloid; D012996:Solutions; D005934:Glucagon