LAUSR

Time-resolved tools for activating proteins of interest in living systems can allow monitoring of the dynamics of biological processes such as signal transduction. Various approaches have been developed to engineer both constitutive and inducible protein activation (e.g. genetic fusion of light switchable proteins). Active-site decaging is another strategy, but the limited number of genetically encoded unnatural amino acids and associated decaging reactions restricts its use to a limited number of protein families. Professor Peng Chen and Professor Chu Wang from the College of Chemistry and Molecular Engineering at Peking University have recently reported a universal protein-activation method in living systems, enabled by computational protein design [1], that they describe as ‘proximal decaging’. The Chen lab has previously developed bioorthogonal cleavage reactions to perform gainof-function studies of protein families such as kinases by genetically encoded active-site decaging [2,3]. In collaboration with the Wang group, which has deep expertise in bioinformatics and computational modeling for discovering and manipulating functional sites in proteomes, they sought to introduce a photo-caged tyrosine (ONBY) as a universal ‘cage’ at a site near, but not in, the catalytic center of the target protein or enzyme. The caged amino acid blocks protein activity but, upon decaging, the protein activity is immediately unleashed, even in a complex proteome (Fig. 1). The strategy goes beyond traditional active-site-based methods by targeting the substrate/cofactor binding pocket and is in principle capable of controlling the function of almost any protein of interest. In order to identify suitable sites for ONBY insertion in an unbiased way, the Wang group employed Rosetta [4] to systematically calculate the impact on protein stability and substrate binding of the introduced tyrosine both with and