Design of a Human Rhinovirus-14 3C Protease-Inducible Caspase-3

The engineering of enzymes for the purpose of controlling their activity represents a valuable approach to address challenges in both fundamental and applied research. Here, we describe and compare different design strategies for the generation of a human rhinovirus-14 (HRV14) 3C protease-inducible caspase-3 (CASP3). We exemplify the application potential of the resulting protease by controlling the activity of a synthetic enzyme cascade, which represents an important motif for the design of artificial signal transduction networks. In addition, we use our engineered CASP3 to characterize the effect of aspartate mutations on enzymatic activity. Besides the identification of mutations that render the enzyme inactive, we find the CASP3-D192E mutant (aspartate-to-glutamate exchange at position 192) to be inaccessible for 3C protease-mediated cleavage. This indicates a structural change of CASP3 that goes beyond a slight misalignment of the catalytic triad. This study could inspire the design of additional engineered proteases that could be used to unravel fundamental research questions or to expand the collection of biological parts for the design of synthetic signaling pathways.