Fig. 2: Single-particle reconstruction of complexed 6HB structures using cryo-EM.

a, Representative micrograph image of 6HB coated with a single protein layer (6HB-2k). b, Selected 2D class averages for 6HB-2k. c, Cryo-EM density of the tube (left) and a selected hexamer (top right). In an atomic model (bottom right) the CP (PDB:1cwp) was flexibly fitted to the EM density. d, Representative image of the double-layered filaments formed by 6HB and the CPs (6HB-10k). e, Selected 2D class averages for 6HB-10k. f, Cryo-EM density of the outer layer of a double-layered tube. g, Cross section and top view of 6HB-2k complexes showing the DNA origami in blue. h, Electrostatic potential surface suggests a negative potential for both the DNA origami (left) and the outward-facing protein surface of the first layer (top right), whereas the DNA adjacent surface of the protein shell (bottom right) possesses a positive potential. i, A 3D model of the assembled double-layer structure shows the different symmetry of the two layers assembling on 6HB origami (1). While the inner layer (2) has a 1-start helix symmetry, the outer layer (3) is defined by a 3-start helix.