The split protein system based on the inducible dimerization is an attractive method to regulate the protease activity. Wehr et al. Wehr2006 described a split TEVp expressed as two functionally inactive fragments; the N-terminal (1 – 118 aa) and C-terminal (119 – 242 aa) protease fragments (referred to as cTEVp and nTEVp). When the two fragments were coexpressed as fusion constructs with adjacent dimerization partners, the split TEVp was able to reconstitute and regain its catalytic activity, demonstrating that the activity of split TEVp could be controlled through the ligand induced protein – protein interactions.

Our team hypothesized that the same inducible dimerization approach could also be used with TEVp homologues. We converted all of the tested orthogonal potyviral proteases to split proteases by splitting them at positions corresponding to the position of the previously described split TEV protease. We selected three different types of dimerization domains to induce the activity of the split proteases. The first pair of dimerization domains was the rapamycin responsive FKBP/FRB system Banaszynski , which induces dimerization upon ligand binding. The second pair of dimerization domains was the CRY2PHR/CIBN system, which induces dimerization upon irradiation with blue light. Finally, our third system for dimerization was designed to respond to a Ca2+ influx based on the calmodulin-M13 interaction , that we used to detect mechanosensing.