Intein-mediated synthesis of proteins containing carbohydrates and other molecular probes

We report here the use of an intein-mediated protein ligation strategy for the synthesis of glycoproteins and proteins containing various molecular pr obes. Several simple cysteine derivatives are synthesized and used as nucle ophiles for specific incorporation onto the C-terminus of proteins expresse d as N-terminal intein fusions. Examples of C-terminal carbohydrate labelin g, fluorescence labeling, incorporation of a metal chelator, and incorporat ion of a nucleotide are presented.