Selective covalent binding of methionyl-containing peptides and proteins to water insoluble polymeric reagent and their regeneration

A polymeric reagent of the type P approximately NHCOCH2Cl (where P is Bio-Gel P-100) was prepared. This polymer covalently bound peptides and proteins specifically at methionine residues under acidic conditions in the presence of a small amount of sodium iodide. Treatment of the polymer-peptide conjugate with 2-mercaptoethanol resulted in essentially complete removal of the peptide with regeneration of intact methionyl residues. In an alternative way, the polymer was suspended for 2 h in boiling water. This treatment resulted in the conversion of the bound methionyl residues to homoserine residues and cleavage and liberation of the bound peptides. The polymeric reagent was successfully applied to the separation of methionyl peptides from peptide mixtures and for specific covalent binding of enzymes and biologically active proteins via their exposed methionyl residues, with the retention of their biological activity.