Figure 1.

Transformation of the versatile covalent proteasome inhibitor MG132 into a blue‐light‐controlled biomolecular tool MG132‐Cage (1) enabling spatio‐temporal control of various fundamental biological phenomena. The reactive aldehyde anchorpoint of MG132 is caged by a photolabile protecting group in the form of an acetal rendering the resulting compound MG132‐Cage (1) fully inactive. Upon blue‐light irradiation the aldehyde function is restored and covalent proteasome binding and inhibition is triggered.