Enzymatic Peptide and Protein Bromination: The BromoTrp Tag.

Bio-orthogonal reactions for modification of proteins and unprotected peptides are of high value in chemical biology. The combination of enzymatic halogenation with transition metal-catalyzed cross-coupling provides a feasible approach for the modification of proteins and unprotected peptides. By a semirational protein engineering approach, variants of the tryptophan 6-halogenase Thal were identified that enable efficient bromination of peptides with a C-terminal tryptophan residue.