Disulfide Bond Location in Proteins

Abstract

The sulfhydryl groups of cysteine residues are among the most reactive side chains in proteins. Free sulfhydryl groups of
cysteines are often involved in the active sites for enzymatic catalysis, as in cysteine proteases (1,2). Common reactions of free sulflhydryl groups include oxidation to form cysteic acids and disulfide bonds. Disulfide bonds
in proteins play an important role in the folding and refolding process, and in stabilizing the three-dimensional structure
of the molecule (3). Although the amino acid sequences of proteins can be deduced from the corresponding cDNA sequences, the state and connectivity
of the cysteine residues after translation cannot be predicted accurately. Characterization of disulfide linkages in proteins
has become an essential part of the analysis of recombinant DNA products, because molecules having incorrect disulfide linkages
may have much lower activity than that of the desired product. Therefore, it is important to verify that recombinant materials
have the correct disulfide linkages.