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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 
 
 

Thermal destruction processes in proteins involving cystine residues.

To ascertain the upper limit of protein thermostability and to evaluate the introduction of additional -S-S- bridges for the enhancement of protein thermostability by site-directed mutagenesis, the stability of cystine residues at 100 degrees C has been investigated in a number of unrelated proteins. All proteins studied (more than a dozen) undergo heat-induced beta-elimination of cystine residues in the pH range from 4 to 8. The time courses of this process closely follow first-order kinetics indicating that the stability of a cystine residue is not significantly affected by its position in the polypeptide chain. Furthermore, the first-order rate constants of beta-elimination of disulfide bonds at 100 degrees C are remarkably similar for different proteins--0.8 +/- 0.3 h-1 and 0.06 +/- 0.02 h-1 at pH 8.0 and 6.0, respectively. Thus, this process is relatively independent of both the primary structure and the elements of higher structures remaining in proteins in 100 degrees C. beta-Elimination of disulfides produces free thiols that cause yet another deleterious reaction in proteins--heat-induced disulfide interchange. This reshuffling of -S-S-bonds, which is much faster than beta-elimination, has also been quantitatively characterized.[1]

References

  1. Thermal destruction processes in proteins involving cystine residues. Volkin, D.B., Klibanov, A.M. J. Biol. Chem. (1987) [Pubmed]
 
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