Mapping the transition state of the WW domain beta-sheet.
The folding kinetics of a three-stranded antiparallel beta-sheet (WW domain) have been measured by temperature jump relaxation. Folding and activation free energies were determined as a function of temperature for both the wild-type and the mutant domain, W39F, which modifies the beta(2)-beta(3) hydrophobic interface. The folding rate decreases at higher temperatures as a result of the increase in the activation free energy for folding. Phi-Values were obtained for thermal perturbations allowing the primary features of the folding free energy surface to be determined. The results of this analysis indicate a significant shift from an "early" (Phi(T)=0. 4) to a "late" (Phi(T)=0.8) transition state with increasing temperature. The temperature-dependent Phi-value analysis of the wild-type WW domain and of its more stable W39F hydrophobic cluster mutant reveals little participation of residue 39 in the transition state at lower temperature. As the temperature is raised, hydrophobic interactions at the beta(2)-beta(3) interface gain importance in the transition state and the barrier height of the wild-type, which contains the larger tryptophan residue, increases more slowly than the barrier height of the mutant.
Crane
J C
JC
School of Chemical Sciences and Beckman Institute for Advanced Science and Technology, Urbana, IL 61801, USA.
Koepf
E K
EK
Kelly
J W
JW
Gruebele
M
M
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002942:Circular Dichroism; D005453:Fluorescence; D006801:Humans; D007700:Kinetics; D007834:Lasers; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010750:Phosphoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013696:Temperature; D013816:Thermodynamics; D014157:Transcription Factors; D014364:Tryptophan / Q000378:metabolism; D000091102:YAP-Signaling Proteins
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D010750:Phosphoproteins; D014157:Transcription Factors; D000091102:YAP-Signaling Proteins; C088374:YAP1 protein, human; D014364:Tryptophan