Analysis of Cyst(e)ine Residues, Disulfide Bridges, and Sulfhydryl Groups in Proteins

Abstract

The presence and the state of cysteine and cystine residues often have considerable influence on the properties, the structure, and the function of a protein. The sulfhydryl groups of the cysteine residues are in most cases the most reactive functional side chains of the protein. They can easily be oxidized or otherwise modified. They are often of importance for the biological acitivity of the protein. The disulfide bonds of the cystine residues contribute in a unique way to the protein’s spatial structure and to the stability of this structure. Proteins may contain only cysteine residues, only cystine residues, or a mixture of both. In certain proteins post-translationally derivatized sulfhydryl groups have been shown to exist. Obviously, proteins may also be devoid of cyst(e)ine.