Biology as Poetry: Biochemistry

Bacteriophage Ecology Group

Disulfide Bridge

Protein tertiary structure linkage involving the interaction between two cysteine amino acid R groups.

As with much of protein tertiary structure, the interacting amino acids are not adjacent in the polypeptide chain but instead often are quite distant from each other. The actual linkage takes on the form of C-S-S-C where each of the sulfur atoms are supplied by different cysteine moieties in the course of oxidation of their sulfhydryl groups.

Forced reduction, as is typically done in the course of protein gel electrophoresis (i.e., SDS-PAGE), reverses the oxidation, thereby breaking the disulfide bridge. The result is proteins which are more fully denatured and therefore which traverse the gel more as a function of their molecular weight than as a function of their folded conformation.

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