SYSTEM FOR COVALENTLY LINKING PROTEINS

The present invention relates to a system for generating intermolecular covalent bonds (e.g. amide, e.g. isopeptide bonds) between polypeptides. In particular, it provides the use of a chimeric protein to generate an anhydride group on a polypeptide for the formation of a covalent bond, wherein the chimeric protein comprises (i) a domain comprising the polypeptide and (ii) a domain comprising a self-processing module that contains an N-terminal dipeptide of aspartate or glutamate and proline (D/E-P), wherein (i) and (ii) are linked by a peptide bond between the aspartate or glutamate residue at the N-terminus of (ii) and the amino acid at the C-terminus of (i) and wherein the self-processing module cleaves the peptide bond between the proline residue and the aspartate or glutamate residue in the self-processing module to release the polypeptide and generate the anhydride group on the aspartate or glutamate residue.