title: Polyproline helices in protein structures: A statistical survey.
abstract: A statistical survey of polyproline II (PPII) helices extracted from protein crystal structures is here reported. The average hydrophobicity of these helices is intermediate between those displayed by beta-strands and coil regions and is similar to that of alpha-helices. PPII helices with amphipathic properties have been identified and classified. Amino acid propensities for PPII helices derived in this study differ significantly from those previously reported. They show a little albeit significant correlation with propensities for alpha-helices whereas they are fully non-correlated to propensities for beta-sheets. Finally, PPII propensities have been correlated with amino acid frequencies in structural proteins, such as collagen and extensins.
authors.affiliation: Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone 16. I-80134 Napoli, Italy.
authors.forename: Rita
authors.initials: R
authors.lastname: Berisio
authors.forename: Salvatore
authors.initials: S
authors.lastname: Loguercio
authors.forename: Alfonso
authors.initials: A
authors.lastname: De Simone
authors.forename: Adriana
authors.initials: A
authors.lastname: Zagari
authors.forename: Luigi
authors.initials: L
authors.lastname: Vitagliano
mesh_terms: D000465:Algorithms; D019295:Computational Biology / Q000379:methods; D030562:Databases, Protein / Q000706:statistics & numerical data; D015233:Models, Statistical; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary
chemical_list: D010455:Peptides; C011083:polyproline