Figure 4.

Tunable proteolysis in S. mutans. To engineer tunable proteolysis onto a target protein, the corresponding target gene (orange) is fused to a chimeric tag encoding the small ubiquitin-like protein NEDD8 (green) followed by an endogenous S. mutans degron (red). The protein chimera will remain stable until the NEDD8-specific endopeptidase NEDP1 (scissor icon) is produced. In this system, NEDP1 is ectopically expressed under the transcriptional control of the Xyl-S1 cassette (brown), which is induced by the sugar xylose. In the presence of xylose, repression of NEDP1 is relieved, NEDP1 is produced, and NEDD8 is subsequently cleaved from the target protein. This exposes the N-degron at the new N-terminus of the protein, which targets the protein for highly efficient Clp- and/or FtsH-mediated proteolysis.