REVERSIBLE MODIFICATION OF LYSINE IN β‐LACTOGLOBULIN USING CITRACONIC ANHYDRIDE

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Abstract
Acylation of lysine in .beta.-lactoglobulin-B with citraconic anhydride resulted in a loss of the free sulfhydryl groups. These were not regenerated under the conditions used to remove the modifying groups from lysine. Gel filtration and polyacrylamide gel electrophoresis of the citraconylated and decitraconylated .beta.-lactoglobulin showed the presence of high MW components. Modification of sulfhydryl groups with N-ethylmaleimide prior to citraconylation prevented the formation of these high MW components. The heterogeneity of the decitraconylated protein was attributed to a combination of intermolecular disulfide bonding of subunits caused by structural changes occurring during lysine modification and to alkylation of free sulfhydryl groups via the citraconyl double bond.