Conjugation of Glycopeptide Thioesters to Expressed Protein Fragments: Semisynthesis of Glycosylated Interleukin-2

This method describes the conjugation of a synthetic glycopeptide to the N-terminus of a recombinant human interleukin-2 (IL-2) protein fragment. The IL-2 protein fragment is produced as an affinity-tagged fusion protein in Escherichia coli and then cleaved with the highly selective TEV protease to remove the affinity tag and uncover an N-terminal cysteine. The N-terminal cysteine is then used in native chemical ligation reaction to join the IL-2 protein fragment to a glycosylated tripeptide thioester that had been previously synthesized to produce a glycosylated form of IL-2.