title: Beta-sheet folding of 11-kDa fibrillogenic polypeptide is completely aggregation driven.
abstract: A de novo polypeptide GH(6)[(GA)(3)GY(GA)(3)GE](8)GAH(6) (YE8) was designed and genetically engineered to form antiparallel beta-strands of GAGAGA repeats. Modulation of pH enables control of solubility, folding, and aggregation of YE8 by control of the overall polypeptide charge, a consequence of the protonation or deprotonation of the glutamic acid and histidine residues. YE8 exhibits all the major properties of a fibrillogenic protein providing an excellent model for detailed study of the fibrillation. At neutral pH, YE8 is soluble in disordered form, yet at pH 3.5 folds into a predominantly beta-sheet conformation that is fibrillogenic. Atomic force microscopy and transmission electron microscopy indicated the formation of fibrillar aggregates on well-defined, hydrophobic surfaces. The beta-sheet folding of YE8 exhibited a lag phase that could be eliminated by seeding or stirring. The strong dependence of lag time on polypeptide concentration established the limiting step in aggregation as initiation of beta-sheet folding.
authors: Department of Chemistry, University at Albany, SUNY, 1400 Washington Avenue, Albany, NY 12222, USA.
authors: Natalya I
authors: NI
authors: Topilina
authors: Vladimir V
authors: VV
authors: Ermolenkov
authors: Seiichiro
authors: S
authors: Higashiya
authors: John T
authors: JT
authors: Welch
authors: Igor K
authors: IK
authors: Lednev
mesh_terms: D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008970:Molecular Weight; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism*; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D013059:Spectrum Analysis, Raman
chemical_list: D010455:Peptides