Protein folding - Linking catalysts to chemistry

Proteins destined to act outside the confines of the cell need to be able to resist oxidizing processes that might unfold and destroy them. To do this they contain covalent (disulphide) bonds between cysteine residues. A huge step in understanding how these bonds are formed now comes with the first observation that protein disulphide isomerases form a direct link with partly made proteins in the endoplasmic reticulum.