Intracellular Protein Photoactivation Using Sterically Bulky Caging

Methods for intracellular protein photoactivation have been studied to elucidate the spatial and temporal roles of proteins of interest. In this study, an intracellular protein photoactivation method was developed using sterically bulky caging. The protein of interest was modified with biotin via a photocleavable linker, and then conjugated with streptavidin to sterically block the protein surface for inactivation. The caged protein was transduced into cells and reactivated by light‐induced degradation of the conjugates. A cytotoxic protein, saporin, was caged and photoactivated both in vitro and in living cells with this method. This method achieved control of the cytotoxic activity in an off‐on manner, introducing cell death selectively at the designed location using light. This simple and versatile photoactivation method is a promising tool for studying spatio‐temporal cellular events that are related to intracellular proteins of interest. A new method for intracellular protein photoactivation is reported. The protein of interest was biotinylated through a photodegradable linker and then conjugated with streptavidin for steric hinderance, via biotin‐streptavidin binding. This caged protein was transduced into living cells and activated inside the cells by light‐induced degradation of the conjugates.