The Chemical Synthesis of Site-Specifically Modified Proteins Via Diselenide-Selenoester Ligation.

Peptide ligation techniques enable the controlled chemical synthesis of native and engineered proteins, including examples that display site-specific post-translational modifications (PTMs) and non-proteinogenic functionality. Diselenide-selenoester ligation (DSL) is a recent addition to the synthetic methodology that offers several advantages over existing strategies. The standard DSL reaction involves the additive-free ligation of a peptide carrying an N-terminal selenocysteine (Sec) residue with a fragment bearing a C-terminal selenoester. This operationally simple ligation proceeds rapidly at sterically hindered junctions and is efficient across a broad pH range. The incorporation of deselenization and oxidative deselenization techniques into the DSL protocol enables conversion of the Sec residue at the ligation site to alanine (Ala) and serine (Ser), respectively, thus enhancing the scope and versatility of the method. In this chapter, we describe the application of DSL to the one-pot chemical synthesis of proteins via both two-component and three-component ligation pathways.