Light-mediated liberation of enzymatic activity: "small molecule" caged protein equivalents.

Light-activatable ("caged") proteins have been used to correlate, with exquisite temporal and spatial control, intracellular biochemical action with global cellular behavior. However, the chemical or genetic construction of caged proteins is nontrivial, with subsequent laborious introduction into living cells, potentially problematic competition with natural endogenous counterparts, and challenging intracellular incorporation at levels equivalent to the natural enzymes. We describe the design, synthesis, and characterization of small molecular equivalents of a caged Src kinase. These compounds are easy to prepare and function by inhibiting the action of the natural unmodified enzyme.