Download MendeleyStructural Features of Cytochrome c' Folding Intermediates Revealed by Fluorescence Energy-Transfer Kinetics
Lee, J.C., Engman, K.C., Tezcan, F.A., Gray, H.B., Winkler, J.R.(2002) Proc Natl Acad Sci U S A 99: 14778-14782
- PubMed: 12407175
- DOI: https://doi.org/10.1073/pnas.192574099
- Primary Citation of Related Structures:
1MQV - PubMed Abstract:
We employed fluorescence energy-transfer probes to investigate the polypeptide dynamics accompanying cytochrome c' folding. Analysis of fluorescence energy-transfer kinetics from wild-type Trp-72 or Trp-32 in a crystallographically characterized (1.78 A) Q1A/F32W/W72F mutant shows that there is structural heterogeneity in denatured cytochrome c'. Even at guanidine hydrochloride concentrations well beyond the unfolding transition, a substantial fraction of the polypeptides ( approximately 50%) adopts compact conformations (tryptophan-to-heme distance, approximately 25 A) in both pseudo-wild-type (Q1A) and mutant proteins. A burst phase (< or =5 ms) is revealed when stopped flow-triggered refolding is probed by tryptophan intensity: measurements on the Q1A protein show that approximately 75% of the Trp-72 fluorescence (83% for Trp-32) is quenched within the mixing deadtime, suggesting that most of the polypeptides have collapsed.
Organizational Affiliation:
Beckman Institute, California Institute of Technology, Pasadena 91125, USA.
