Stability of the residual structure in unfolded BPTI in different conditions of temperature and solvent composition measured by disulphide kinetics and double mutant cycle analysis
K. Zdanowski et M. Dadlez, Stability of the residual structure in unfolded BPTI in different conditions of temperature and solvent composition measured by disulphide kinetics and double mutant cycle analysis, J MOL BIOL, 287(2), 1999, pp. 433-445
The folding funnel model proposes a clear description of the protein foldin
g process. To test this model, additional data on the structures populated
in different stages of folding and their influence on further folding are r
equired. Here, we use the double mutant strategy and disulphide formation k
inetics measurements to study the impact on folding of the residual structu
re in unfolded bovine pancreatic trypsin inhibitor (BPTI). We show how five
amino acid residues stabilise a folding initiation site, possibly a beta-h
airpin, and influence the shape of the upper region of the folding funnel i
n BPTI in different conditions of temperature and solvent composition. Our
data provide experimental evidence for the mechanism by which a fast search
for a proper chain topology is made possible early in the folding of prote
ins. The results apply to proteins in general, not necessarily just to disu
lphide bonded proteins, since cysteine residues are used here merely as rep
orter groups. (C) 1999 Academic Press.