title: The role of side-chain interactions in the early steps of aggregation: Molecular dynamics simulations of an amyloid-forming peptide from the yeast prion Sup35.
abstract: Understanding the early steps of aggregation at atomic detail might be crucial for the rational design of therapeutics preventing diseases associated with amyloid deposits. In this paper, aggregation of the heptapeptide GNNQQNY, from the N-terminal prion-determining domain of the yeast protein Sup35, was studied by 20 molecular dynamics runs for a total simulation time of 20 micros. The simulations generate in-register parallel packing of GNNQQNY beta-strands that is consistent with x-ray diffraction and Fourier transform infrared data. The statistically preferred aggregation pathway does not correspond to a purely downhill profile of the energy surface because of the presence of enthalpic barriers that originate from out-of-register interactions. The parallel beta-sheet arrangement is favored over the antiparallel because of side-chain contacts; in particular, stacking interactions of the tyrosine rings and hydrogen bonds between amide groups. No ordered aggregation was found in control simulations with the mutant sequence SQNGNQQRG in accord with experimental data and the strong sequence dependence of aggregation.
authors.affiliation: Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
authors.forename: Jörg
authors.initials: J
authors.lastname: Gsponer
authors.forename: Urs
authors.initials: U
authors.lastname: Haberthür
authors.forename: Amedeo
authors.initials: A
authors.lastname: Caflisch
mesh_terms: D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000682:Amyloid / Q000096:biosynthesis*; D005656:Fungal Proteins / Q000737:chemistry*; D010454:Peptide Termination Factors; D011328:Prions / Q000737:chemistry*; D011487:Protein Conformation; D029701:Saccharomyces cerevisiae Proteins; D014443:Tyrosine / Q000737:chemistry
chemical_list: D000682:Amyloid; D005656:Fungal Proteins; D010454:Peptide Termination Factors; D011328:Prions; C068068:SUP35 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014443:Tyrosine; D000409:Alanine