Upper limit of the time scale for diffusion and chain collapse in chymotrypsin inhibitor 2.
The rates of folding of wild-type chymotrypsin inhibitor 2 (CI2) (t1/2 = 12 ms) and of faster (t1/2 = 2 ms) and slower (t1/2 = 350 ms) folding mutants are accelerated in parallel by increasing concentrations of sucrose, despite the increases in viscosity. At a viscosity 26 times that of water, the folding rate constant of wild-type CI2 is accelerated four-fold (t1/2 = 2.7 ms). From this, we can estimate that the diffusional chain collapse in CI2 occurs in less than 100 micros in water, and is not rate-determining in folding.
Ladurner
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AG
Cambridge University Chemical Laboratory and Cambridge Centre for Protein Engineering, Medical Research Council Centre, UK.
Fersht
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AR
D000818:Animals; D002918:Chymotrypsin / Q000037:antagonists & inhibitors; D006801:Humans; D009154:Mutation; D010455:Peptides / Q000737:chemistry* / Q000235:genetics; D010940:Plant Proteins; D017510:Protein Folding
D010455:Peptides; D010940:Plant Proteins; C093336:chymotrypsin inhibitor 2; D002918:Chymotrypsin