Refolding rates

Plaxco K. W Simons K. T. and Baker D. Contact order, transition state placement and the refolding rates of single domain proteins. J. Mol. Biol. (1998) 277(4) 985-994. 

Figure 19.22 The gatekeeping or filtering activity of the GroEL ATPase. The turnover number for the ATPase reaction (0.05-0.1 s-"1) is far slower than the refolding rate constant of 2-2.5 s-1 for GroEL-bound bamase. Only slowly folding proteins bind long enough to enter the chaperoning cycles of Figure 19.23.

If the equilibrium constant for the unfolding can also be determined, then the refolding rate constant, kfold, niay also be determined. 

Thus, the D/H exchange rate must be much faster than the refolding rate. The relative abundance of the two envelopes thus provides a direct measure of the relative concentrations of folded and unfolded protein. (Although the two distributions do not overlap in this example, deconvolution of the natural-abundance isotope distribution... 

The four disulfide bonds of nine homologous short neurotoxins were cleaved by reduced dithiothreitol. The kinetics of refolding, induced by air reoxidation or in the presence of thiol-disulfide exchange reagents, indicated differences in refolding rates. Three toxins refolded 4-10 times more slowly than the six others. It was proposed from consideration of the sequence that a single additional amino acid insertion is responsible for these differences (Menez et al, 1980). These data indicate the role of noncovalent interactions in the formation of disulfide bridges. 

---