In a new paper in ChemBioChem, researchers from the Hedstrom lab describe a novel method for protein labeling that is versatile and selective.  The method involves the modification of HA tags (a short amino acid sequence commonly used as an epitope tag that contains several tyrosines) selectively in a variety of ways using mushroom tyrosinase. This cheap and versatile chemical biological tool can effect HA tag cleavage, aggregation, or functionalization by changing conditions. The method for dye-labeling HA-tagged proteins has been applied in both E coli and mammalian cell lysates.

Long MJ, Hedstrom L. Mushroom Tyrosinase Oxidizes Tyrosine-Rich Sequences to Allow Selective Protein Functionalization. Chembiochem : a European journal of chemical biology. 2012. (DOI: 10.1002/cbic.201100792)