Mimicking Phosphorylation

A new adaptation of classic reactivity constructs phosphorylated protein mimics without using enzymes. The new reaction sequence is related to the Staudinger ligation, which is widely used for labeling biomolecules, and adds to the tool kit for probing biological signaling pathways. Christian P. R. Hackenberger of the Free University of Berlin and coworkers adapted the Staudinger-phosphite reaction, which forms phosphoramidates from the combination of phosphites and azides, to work under aqueous conditions at room temperature. Next, they ran the reaction with a specially designed phosphite that loses masking groups in the presence of light. That produced charged phosphoramidates, which differ from phosphates only by the replacement of an oxygen atom with an NH group. With that process, they site-selectively incorporated phosphotyrosine mimics into a protein, which was recognizable by a phosphotyrosine-specific antibody (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200902118). The differential chemical and enzymatic reactivity of phosphates and phosphoramidates is a bonus of this work that could be exploited in future studies, says chemical biologist Ronald T. Raines of the University of Wisconsin, Madison.