Protein Cages and Nanostructures Constructed from Protein Nanobuilding Blocks.

Protein cages and nanostructures are promising biocompatible medical materials, such as vaccines and drug carriers. Recent advances in designed protein nanocages and nanostructures have opened up cutting-edge applications in the fields of synthetic biology and biopharmaceuticals. A simple approach for constructing self-assembling protein nanocages and nanostructures is the design of a fusion protein composed of two different proteins forming symmetric oligomers. In this chapter, we describe the design and methods of protein nanobuilding blocks (PN-Blocks) using a dimeric de novo protein WA20 to construct self-assembling protein cages and nanostructures. A protein nanobuilding block (PN-Block), WA20-foldon, was developed by fusing an intermolecularly folded dimeric de novo protein WA20 and a trimeric foldon domain from bacteriophage T4 fibritin. The WA20-foldon self-assembled into several oligomeric nanoarchitectures in multiples of 6-mer. De novo extender protein nanobuilding blocks (ePN-Blocks) were also developed by fusing tandemly two WA20 with various linkers, to construct self-assembling cyclized and extended chain-like nanostructures. These PN-Blocks would be useful for the construction of self-assembling protein cages and nanostructures and their potential applications in the future.