title: Evaluating beta-turn mimics as beta-sheet folding nucleators.
abstract: Beta-turns are common conformations that enable proteins to adopt globular structures, and their formation is often rate limiting for folding. Beta-turn mimics, molecules that replace the i + 1 and i + 2 amino acid residues of a beta-turn, are envisioned to act as folding nucleators by preorganizing the pendant polypeptide chains, thereby lowering the activation barrier for beta-sheet formation. However, the crucial kinetic experiments to demonstrate that beta-turn mimics can act as strong nucleators in the context of a cooperatively folding protein have not been reported. We have incorporated 6 beta-turn mimics simulating varied beta-turn types in place of 2 residues in an engineered beta-turn 1 or beta-bulge turn 1 of the Pin 1 WW domain, a three-stranded beta-sheet protein. We present 2 lines of kinetic evidence that the inclusion of beta-turn mimics alters beta-sheet folding rates, enabling us to classify beta-turn mimics into 3 categories: those that are weak nucleators but permit Pin WW folding, native-like nucleators, and strong nucleators. Strong nucleators accelerate folding relative to WW domains incorporating all alpha-amino acid sequences. A solution NMR structure reveals that the native Pin WW beta-sheet structure is retained upon incorporating a strong E-olefin nucleator. These beta-turn mimics can now be used to interrogate protein folding transition state structures and the 2 kinetic analyses presented can be used to assess the nucleation capacity of other beta-turn mimics.
authors.affiliation: Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Amelia A
authors.initials: AA
authors.lastname: Fuller
authors.forename: Deguo
authors.initials: D
authors.lastname: Du
authors.forename: Feng
authors.initials: F
authors.lastname: Liu
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Davoren
authors.forename: Gira
authors.initials: G
authors.lastname: Bhabha
authors.forename: Gerard
authors.initials: G
authors.lastname: Kroon
authors.forename: David A
authors.initials: DA
authors.lastname: Case
authors.forename: H Jane
authors.initials: HJ
authors.lastname: Dyson
authors.forename: Evan T
authors.initials: ET
authors.lastname: Powers
authors.forename: Peter
authors.initials: P
authors.lastname: Wipf
authors.forename: Martin
authors.initials: M
authors.lastname: Gruebele
authors.forename: Jeffery W
authors.initials: JW
authors.lastname: Kelly
mesh_terms: D000595:Amino Acid Sequence; D006801:Humans; D007700:Kinetics; D018716:Molecular Mimicry; D008969:Molecular Sequence Data; D050505:Mutant Proteins; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D019696:Peptidylprolyl Isomerase / Q000737:chemistry*; D055550:Protein Stability; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012996:Solutions; D013816:Thermodynamics
chemical_list: D050505:Mutant Proteins; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D012996:Solutions; C000606846:PIN1 protein, human; D019696:Peptidylprolyl Isomerase