Folding of a heterogeneous β-hairpin peptide from temperature-jump 2D IR spectroscopy

Proc Natl Acad Sci U S A. 2013 Feb 19;110(8):2828-33. doi: 10.1073/pnas.1211968110. Epub 2013 Feb 4.

Abstract

We provide a time- and structure-resolved characterization of the folding of the heterogeneous β-hairpin peptide Tryptophan Zipper 2 (Trpzip2) using 2D IR spectroscopy. The amide I' vibrations of three Trpzip2 isotopologues are used as a local probe of the midstrand contacts, β-turn, and overall β-sheet content. Our experiments distinguish between a folded state with a type I' β-turn and a misfolded state with a bulged turn, providing evidence for distinct conformations of the peptide backbone. Transient 2D IR spectroscopy at 45 °C following a laser temperature jump tracks the nanosecond and microsecond kinetics of unfolding and the exchange between conformers. Hydrogen bonds to the peptide backbone are loosened rapidly compared with the 5-ns temperature jump. Subsequently, all relaxation kinetics are characterized by an observed 1.2 ± 0.2-μs exponential. Our time-dependent 2D IR spectra are explained in terms of folding of either native or nonnative contacts from a common compact disordered state. Conversion from the disordered state to the folded state is consistent with a zip-out folding mechanism.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Hydrogen Bonding
  • Kinetics
  • Peptides / chemistry*
  • Protein Folding*
  • Spectrophotometry, Infrared / methods*
  • Temperature*

Substances

  • Peptides