Post-Translational Modifications of Protein-Nanocages As a Universal Biosensor Platform

Biosensors that can convert recognition of an analyte to easily measurable signals are highly desired. A typical sensor is composed of three components to realize its functions: detection moieties, output domains and a platform to connect the two components. Bio-generated nano-biosensors are preferred as platform because of the high surface-area-to-volume ratio and their bio-friendly nature. Nowadays, different context-driven biosensors, in which application determines the type of components needed for sensor assembly, are developed. However, current strategies for bionanoparticle decoration, including chemical modification, direct genetic fusion and click chemistry, suffer from unfavorable spacing and orientation of cargos or particle instability problems. To address these problems, we developed a new biological strategy based on post-translational modifications of bionanoparticles. The E2 core of the pyruvate dehydrogenase complex from Bacillus stearothermophilus, a genetically-modifiable 60-mer protein nanocage of 27nm diameter, was used as the model platform. Sortase A was used to allow precise covalent decoration of E2 nanocages with different input domains, purification domains and signal output domains with desired orientations and ratios to achieve universal, sensitive target detection, and easy purification. Also the potential of this platform for drug delivery into cancer cells will be discussed.