Total Chemical Synthesis of the Enzyme Sortase A ΔN59 with Full Catalytic Activity

The enzyme sortase A is a ligase which catalyzes transpeptidation reactions.1, 2 Surface proteins, including virulence factors, that have a C terminal recognition sequence are attached to Gly 5 on the peptidoglycan of bacterial cell walls by sortase A.1 The enzyme is an important anti‐virulence and anti‐infective drug target for resistant strains of Gram‐positive bacteria.2 In addition, because sortase A enables the splicing of polypeptide chains, the transpeptidation reaction catalyzed by sortase A is a potentially valuable tool for protein science.3 Here we describe the total chemical synthesis of enzymatically active sortase A. The target 148 residue polypeptide chain of sortase A ΔN59 was synthesized by the convergent chemical ligation of four unprotected synthetic peptide segments. The folded protein molecule was isolated by size‐exclusion chromatography and had full enzymatic activity in a transpeptidation assay. Total synthesis of sortase A will enable more sophisticated engineering of this important enzyme molecule.