Labeling proteins by affinity-guided DMAP chemistry.

Catalysts have long played an essential role in organic synthesis and thus hold potential as tools for chemical protein modification. However, there are only a few examples of catalyst-mediated protein labeling under biological conditions because of the difficulty of designing molecular catalysts that work in aqueous environments with high target selectivity and reaction efficiency. To overcome this situation, we have previously developed a new catalyst-based method, termed affinity-guided DMAP (4-dimethylaminopyridine) (AGD) chemistry, for site-specific protein labeling in a target-selective manner using an acyl transfer reaction. More recently, we discovered that the labeling rate and efficiency can be greatly enhanced by using "multivalent" DMAP groups. Here, we describe the principle of the multivalent AGD chemistry and the protocol for chemical labeling of FK506-binding protein 12 (FKBP12) in test tubes. In this method, the FKBP12 labeling is completed within 30 min and occurs site specifically at the vicinity of the ligand-binding pocket of the protein.