Disulphide-mediated site-directed modification of proteins

Methods for chemical modification of native proteins in a controlled fashion are in high demand. Here, a novel protocol that exploits bifunctional reagents for transient targeting of solvent exposed disulphides to direct the introduction of a single exogenous reactive thiol handle at a lysine side chain has been developed. The protocol has successfully been applied to functionalize six different Fabs and human growth hormone. Site-directed addition of a single thiols handle to proteins by means of temporary disulphide rebridging of solvent exposed disulphides is obtained with a new labelling reagent.