Evaluating beta-turn mimics as beta-sheet folding nucleators.
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.
Fuller
Amelia A
AA
Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
Du
Deguo
D
Liu
Feng
F
Davoren
Jennifer E
JE
Bhabha
Gira
G
Kroon
Gerard
G
Case
David A
DA
Dyson
H Jane
HJ
Powers
Evan T
ET
Wipf
Peter
P
Gruebele
Martin
M
Kelly
Jeffery W
JW
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
D050505:Mutant Proteins; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D012996:Solutions; C000606846:PIN1 protein, human; D019696:Peptidylprolyl Isomerase