Multifunctional Enzyme Packaging and Catalysis in the Qβ Protein Nanoparticle.

The simultaneous expression in Escherichia coli cells of the Qβ virus-like particle (VLP) capsid protein and protein "cargo" tagged with a positively charged Rev peptide sequence leads to the spontaneous self-assembly of VLPs with multiple copies of the cargo inside. We report the packaging of four new enzymes with potential applications in medicine and chemical manufacturing. The captured enzymes are active while inside the nanoparticle shell and are protected from environmental conditions that lead to free-enzyme destruction. We also describe genetic modifications to the packaging scheme that shed light on the self-assembly mechanism of this system and allow indirect control over the internal packaging density of cargo. The technology was extended to create, via self-assembly, VLPs that simultaneously display protein ligands on the exterior and contain enzymes within. Inverse relationships were observed between the size of both the packaged and externally displayed protein or domains and nanoparticle yield. These results provide a general method for the rapid creation of robust protein nanoparticles with desired catalytic and targeting functionalities.