Model of the engineered fusion protein and the resulting octahedral structure formed. (a) The fusions are composed of a trimeric protein (KDPGal aldolase, green) and a dimeric protein (FkpA, orange) with a four residue helical linker (blue). The lines represent the three-fold (cyan) and two-fold (magenta) axes. (b) The 24-mer cage with octahedral symmetry, with the symmetry axes shown. (c) 2D class averages of the 24-mer and 12-mer obtained after aligning, clustering, and average particles from several particles (left) which are consistent with calculated projections (center). The 3D atomic models (right) are also included. Figure reproduced from ref. 13 with permission from Nature Publishing Group, copyright 2014.