Unfolding and Refolding

The unfolding and refolding mechanism of E. coli tryptophanase is summarized in Fig. 9.5 (T. Mizobata and Y. Kawata, unpublished results), where N is the native state, I the intermediate having a tendency toward aggregation, X the irreversible aggregates, and U the unfolded state. At below 2 M Gdn-HCl, holotryptophanase unfolds via apoenzyme (Nhoio--- Napo-- I-- U (or X)), whereas at high concentrations of Gdn-HCl ( 2 M), 

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M. H. Hao, M. R. Pincus, S. Rackovsky, and H. A. Scheraga. Unfolding and refolding of the native structure of bovine pancreatic trypsin inhibitor studied by computer simulations. Biochemistry, 32 9614-9631, 1993. 

Fig. 32. Double-jump experiments of unfolding and refolding. The peptide [(Ala-Gly-Pro)s]3 in 50 ml phosphate buffer (pH 7.5) was incubated at 9.2 °C and quickly unfolded by a first temperature jump from 9.2 to 30 °C. This process took 25 s, the time needed to reach the final temperature. In a first experiment (curve A), the second jump back from 30 to 9.2 °C followed immediately after complete unfolding of the peptide, i.e. 25 s after the first jump. In a second and a third experiment (curve B, C), the time lapse between the first and the second jump was 75 and 125 s, respectively...

Pande V. S. and Rokhsar D. S. Molecular dynamics simulations of unfolding and refolding of a p hairpin fragment of protein G. (1999) (preprint). 

F. X. Schmid, R. Grafl, A. Wrba, and J. J. Beintema, Role of proline peptide bond isomerization in unfolding and refolding of ribonuclease, Proc. Natl. Acad Sci. U.S.A. 83, 872-876 (1986). 

Fig. 4. Equilibrium curves for the unfolding and refolding of penicillinase in guanidinium chloride measured by viscosity (1), difference spectroscopy (2), and mean residue rotation [m jiM (3). Redrawn with permission from Robson and Pain (1976b).

Self-Sorting Processes Control the Folding, Forced Unfolding, and Refolding of an Abiotic Oligomer in Water... 

Scheme 4.10 The sequential addition of various CB[ ] and guests to 41 induces folding, forced unfolding, and refolding of 41 into four different conformations. See insert for color representation of this figure.

Figure 7. Mechanical unfolding of RNA molecules (a, b) and proteins (c, d) using optical tweezers, (a) Experimental setup in RNA pulling experiments, (b) Pulling cycles in the homologous hairpin and force rip distributions during the unfolding and refolding at three pulling speeds. (C) Equivalent setup in proteins, (d) Force extension curve when pulUng the protein RNAseH. Panel (b) is from Ref. 86. Panels (a) and (d) are a courtesy from C. Cecconi [84]. (See color insert.)...

Koepf, E.K., Petrassi, H.M., Sudol, M., and Kelly, J.W. 1999. WW An isolated three-stranded antiparallel P-sheet domain that unfolds and refolds reversibly evidence for a structured hydrophobic cluster in urea and GdnHCl and a disordered thermal unfolded state. Protein Sci. 8 841-853. 

The Fe—Met-80 link is also involved in the unfolding and refolding of the protein in reversible denaturation.673 The last process in the unfolding and the first process during refolding are the disruption and formation of the Fe—Met-80 linkage respectively. 

Zhao GJ, Cheng CL (2012) Molecular dynamics simulation exploration of unfolding and refolding of a ten-amino acid miniprotein. Amino Acids 43(2) 557-565... 

Fig. 9.5 Unfolding and refolding mechanism of E coli tryptophanase. See text for details.

We therefore studied the unfolding and refolding kinetics of authentic and recombinant goat a-lactalbumin, induced by GdnHCl concentration jumps,... 

Most of the small proteins that were used initially as substrates to test the function of prolyl isomerases contained disulfide bonds, which were left intact during unfolding and refolding. These proteins were used because their unfolding is reversible under a wide variety of conditions and because good evidence existed for a number of them that prolyl isomerizations were involved as rate-limiting steps in their slow-folding reactions. A protein chain without disulfides should be a better model... 

VI. Catalysis of Prolyl Isomerization during Unfolding AND Refolding... 

Both disulfide bonds remain intact during unfolding and refolding. 

Figure 5-13. Protein unfolding by chemical denaturation. The unfolding and refolding of proteins caused by the addition of guanidinium chloride (GdnHCI) can be monitored from the CD spectrum, usually at 220 nm. The diagram on the left shows the denaturation curve as expressed by the concentration dependence of...

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