title: Polyproline II propensities from GGXGG peptides reveal an anticorrelation with beta-sheet scales.
abstract: There is growing appreciation of the functional relevance of unfolded proteins in biology. However, unfolded states of proteins have proven inaccessible to the usual techniques for high-resolution structural and energetic characterization. Unfolded states are still generally conceived of as statistical coils, based on the pioneering work of Flory [(1969) Statistical Mechanics of Chain Molecules (Wiley, New York)] and Tanford [(1968) Adv. Protein Chem. 23, 121-282]. Recently, several lines of independent evidence have raised doubts about the random coil model and offer support for alternative views. Here, we show that polyproline II conformation is dominant in a host-guest peptide model AcGGXGGNH(2) (X not equal glycine), in equilibrium predominantly with beta-structure. This result is inconsistent with a random coil model and the general view that these peptides are unstructured. By calculating a set of apparent DeltaG values from the measured coupling constants of the backbone amides, we can construct a polyproline II scale that correlates negatively with beta-sheet scales.
authors.affiliation: Department of Chemistry, New York University, NY 10003, USA.
authors.forename: Zhengshuang
authors.initials: Z
authors.lastname: Shi
authors.forename: Kang
authors.initials: K
authors.lastname: Chen
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Liu
authors.forename: Angela
authors.initials: A
authors.lastname: Ng
authors.forename: W Clay
authors.initials: WC
authors.lastname: Bracken
authors.forename: Neville R
authors.initials: NR
authors.lastname: Kallenbach
mesh_terms: D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009842:Oligopeptides / Q000378:metabolism; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism; D017510:Protein Folding; D017433:Protein Structure, Secondary; D014461:Ultracentrifugation
chemical_list: D009842:Oligopeptides; D010455:Peptides; C011083:polyproline