Self-assembling protein cages have potential applications in nanotechnology which range from drug delivery to constrained materials synthesis. One viral-like assembly is the E2 subunit of the pyruvate dehydrogenase multienzyme complex from Bacillus stearothermophilus. Through protein engineering and gene optimization for expression in E. coli, our E2 protein has been truncated down to its structural core. This yields a 25-nm dodecahedron with a hollow cavity and unusually high stability. This core scaffold exhibits an onset unfolding temperature of 81.1°C and an apparent midpoint unfolding temperature of 91.4°C, and its thermostability is observed between pH 5.0 and 7.4. We have designed variants that can accommodate drug-like molecules in the hollow internal cavity while remaining structurally intact. Furthermore, with this scaffold, we have also introduced the first example of a pH-dependent molecular switch into a virus-like particle. By genetically redesigning the subunit-subunit interfaces, our resulting protein module yields an intact, stable particle at pH 7.4 which dissociates at pH 5.0. This pH-triggered behavior is especially relevant for applications in therapeutic delivery.

Extended Abstract Status: Not Uploaded