A light-activated probe of intracellular protein kinase activity

The first example of a photoactivated probe of intracellular enzymatic activity is described. The caged derivative of a fluorescent protein kinase C peptide-based sensor was prepared by modifying the free hydroxyl group of a phosphorylatable serine moiety with a photolabile appendage that blocks phosphoryl transfer. We have demonstrated that the caged sensor allows one to (1) sample PKC activity with exquisite temporal precision, (2) control the relative amount of active sensor available for phosphorylation, and (3) examine protein kinase activity at multiple time points.