Fig. 5. γ- or δ-Thiol lysine-mediated NCL to generate native ubiquitinated peptide and protein. (A) γ-Thiol lysine-mediated dual NCL to generate native Ub-peptide. (B) δ-Thiol lysine-mediated NCL to generate native Ub-peptide. (C) Genetic incorporation of δ-thiol-Nε-(p-nitrocarbobenzyloxy)lysine for NCL to generate ubiquitinated protein (POI) with a native isopeptide linkage.