Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.27.221333v1?rss=1 Authors: Hsia, Y., Mout, R., Sheffler, W., Edman, N. I., Vulovic, I., Park, Y.-J., Redler, R. L., Bick, M. J., Bera, A. K., Courbet, A., Kang, A., Brunette, T., Nattermann, U., Tsai, E., Saleem, A., Chow, C. M., Ekiert, D. C., Bhabha, G., Veesler, D., Baker, D. Abstract: A goal of de novo protein design is to develop a systematic and robust approach to generating complex nanomaterials from stable building blocks. Due to their structural regularity and simplicity, a wide range of monomeric repeat proteins and oligomeric helical bundle structures have been designed and characterized. Here we describe a stepwise hierarchical approach to building up multi-component symmetric protein assemblies using these structures. We first connect designed helical repeat proteins (DHRs) to designed helical bundle proteins (HBs) to generate a large library of heterodimeric and homooligomeric building blocks; the latter have cyclic symmetries ranging from C2 to C6. All of the building blocks have repeat proteins with accessible termini, which we take advantage of in a second round of architecture guided rigid helical fusion (WORMS) to generate larger symmetric assemblies including C3 and C5 cyclic and D2 dihedral rings, a tetrahedral cage, and a 120 subunit icosahedral cage. Characterization of the structures by small angle x-ray scattering, x-ray crystallography, and cryo-electron microscopy demonstrates that the hierarchical design approach can accurately and robustly generate a wide range of macromolecular assemblies; with a diameter of 43nm, the icosahedral nanocage is the largest structurally validated designed cage to date. The computational methods and building block sets described here provide a very general route to new de novo designed symmetric protein nanomaterials. Copy rights belong to original authors. Visit the link for more info