title: NMR studies of the aggregation of glucagon-like peptide-1: formation of a symmetric helical dimer.
abstract: Nuclear magnetic resonance (NMR) spectroscopy reveals that higher-order aggregates of glucagon-like peptide-1-(7-36)-amide (GLP-1) in pure water at pH 2.5 are disrupted by 35% 2,2,2-trifluoroethanol (TFE), and form a stable and highly symmetric helical self-aggregate. NMR spectra show that the helical structure is identical to that formed by monomeric GLP-1 under the same experimental conditions [Chang et al., Magn. Reson. Chem. 37 (2001) 477-483; Protein Data Bank at RCSB code: 1D0R], while amide proton exchange rates reveal a dramatic increase of the stability of the helices of the self-aggregate. Pulsed-field gradient NMR diffusion experiments show that the TFE-induced helical self-aggregate is a dimer. The experimental data and model calculations indicate that the dimer is a parallel coiled coil, with a few hydrophobic residues on the surface that may cause aggregation in pure water. The results suggest that the coiled coil dimer is an intermediate state towards the formation of higher aggregates, e.g. fibrils.
authors.affiliation: Department of Chemistry, University of Copenhagen, The H.C. Ørsted Institute, Universitetsparken 5, DK-2100 Ø, Copenhagen, Denmark.
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Chang
authors.forename: Danielle
authors.initials: D
authors.lastname: Keller
authors.forename: Seán I
authors.initials: SI
authors.lastname: O'Donoghue
authors.forename: Jens J
authors.initials: JJ
authors.lastname: Led
mesh_terms: D000595:Amino Acid Sequence; D004058:Diffusion; D019281:Dimerization; D005934:Glucagon / Q000737:chemistry*; D052216:Glucagon-Like Peptide 1; D006860:Hydrogen Bonding / Q000187:drug effects; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry*; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D011487:Protein Conformation / Q000187:drug effects; D011498:Protein Precursors / Q000737:chemistry*; D017433:Protein Structure, Secondary / Q000187:drug effects / Q000502:physiology; D014270:Trifluoroethanol / Q000737:chemistry / Q000494:pharmacology; D014867:Water / Q000737:chemistry
chemical_list: D010446:Peptide Fragments; D011498:Protein Precursors; D014867:Water; D014270:Trifluoroethanol; D052216:Glucagon-Like Peptide 1; D005934:Glucagon