title: The structure of "unstructured" regions in peptides and proteins: role of the polyproline II helix in protein folding and recognition.
abstract: Classical descriptions of the three-dimensional shapes of proteins usually invoke three main structures: alpha-helix, beta-sheet, and beta-turn. More recently, the polyproline II (PPII) structure has been implicated in diverse biological activities including signal transduction, transcription, cell motility, and immune response. Concurrently, evidence is accumulating that PPII structure has a significant role in the unfolded states of proteins. In this article, we connect the structural properties of PPII helices to their roles in protein recognition and protein unfolded states. The properties unique to the PPII conformation are linked to the exploitation of this structure for the molecular recognition of proteins, using peptide ligands of the Src homology 3 (SH3) domain as an example. The evidence supporting a role for PPII conformation in protein-unfolded states is also presented in the context of the forces that may stabilize the PPII conformation in unfolded polypeptides.
authors.affiliation: Division of Structural Biology & Biochemistry, Research Institute, Hospital for Sick Children, Toronto M5G 1X8, Ontario, Canada.
authors.forename: Arianna
authors.initials: A
authors.lastname: Rath
authors.forename: Alan R
authors.initials: AR
authors.lastname: Davidson
authors.forename: Charles M
authors.initials: CM
authors.lastname: Deber
mesh_terms: D020816:Amino Acid Motifs; D001665:Binding Sites; D008958:Models, Molecular; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D018909:src Homology Domains
chemical_list: D010455:Peptides; D011506:Proteins; C011083:polyproline