Reductive methylation of lysine residues in casein

Abstract

Summary: The effect of reductive methylation on the properties of α_s-, β- and κ-caseins was studied using preparations of these proteins in which 20 or 60% of the lysyl residues had been reductively methylated. This modification appeared to affect the physicochemical properties of the protein to an insignificant extent and in particular, electrophoretic mobility, sensitivity to precipitation by Ca²⁺and solubility of Ca salts of individual proteins were only slightly altered. The use of caseins which had been subjected to methylation with radioactive formaldehyde is suggested as a potentially valuable method for the study of protein interactions.