DBCO-Gly-Gly-Gly is a water-soluble substrate for the sortase-mediated labelling of proteins (or “Sortagging”). Sortase catalyses a transpeptidase reaction (between a specific internal sequence of a protein and an amine group present on the N-terminus of triglycine) and has also been used in peptide synthesis to cyclize peptides (to create macrocyclic peptides, glycopeptides & protein−protein conjugates). Proteins conjugated to DBCO-Gly-Gly-Gly can be further modified with azide-containing molecules creating site-specific protein conjugates. Examples of creating protein conjugates using sortagging include site-specifically PEGylating proteins, site-specific protein-lipid conjugates, and constructing peptides & glycosylphosphatidylinositol chimeras.