The reaction of protein thiol groups with some disulphides

Abstract

Protein SH groups have been determined by measuring the loss of p-chloromercuribenzoate from solution when the protein is precipitated in the presence of sodium p-chloromercuribenzoate. Incubation with an excess of cystine decreases the SH group content of the serum albumins to zero and of bovine haemoglobin to 50%. GSSG has no effect on the SH content of either protein. The reaction of cystine with the SH groups of bovine serum albumin gives a loss of one molecule of cystine/two protein SH groups. The rate of this reaction follows second-order kinetics and is influenced by pH but not by heavy-metal ions. GSH and cyanide regenerate the SH groups of bovine serum albumin lost in the reaction with cystine.