Mapping the cytochrome C folding landscape.
The solution to the riddle of how a protein folds is encoded in the conformational energy landscape for the constituent polypeptide. Employing fluorescence energy transfer kinetics, we have mapped the S.cerevisiae iso-1 cytochrome c landscape by monitoring the distance between a C-terminal fluorophore and the heme during folding. Within 1 ms after denaturant dilution to native conditions, unfolded protein molecules have evolved into two distinct and rapidly equilibrating populations: a collection of collapsed structures with an average fluorophore-heme distance (r) of 27 A and a roughly equal population of extended polypeptides with r > 50 A. Molecules with the native fold appear on a time scale regulated by heme ligation events ( approximately 300 ms, pH 7). The experimentally derived landscape for folding has a narrow central funnel with a flat upper rim on which collapsed and extended polypeptides interchange rapidly in a search for the native structure.
Lyubovitsky
Julia G
JG
Beckman Institute, California Institute of Technology, Pasadena, California 91125, USA.
Gray
Harry B
HB
Winkler
Jay R
JR
D003574:Cytochrome c Group / Q000737:chemistry*; D004735:Energy Transfer; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry; D006418:Heme / Q000737:chemistry; D007700:Kinetics; D011487:Protein Conformation; D017510:Protein Folding; D012441:Saccharomyces cerevisiae / Q000737:chemistry
D003574:Cytochrome c Group; D005456:Fluorescent Dyes; D006418:Heme