Fig. 2: Atomically ordered structure of ROOL homo-octamer.
From: Naturally ornate RNA-only complexes revealed by cryo-EM
a, Representative micrograph (top; 4,462 micrographs total) with 2D class averages (bottom). Scale bar, 50 nm. b, The 3.1 Å cryo-EM reconstruction of the ROOL complex with D4 symmetry. The map is coloured by 8 labelled chains. In the top view (left), the inner and second circle are labelled. c, Secondary structure of ROOL coloured by domain. Only one chain is shown, in full. Nucleotides involved in intermolecular interactions have been circled in light or dark grey. d,e, Chain 1 is coloured by domain with all other chains in grey. d, Cutaway view, showing chain 1 from the interior of the nanocage with the disordered linker labelled in pink (nucleotides 414–464). e, Intermolecular interactions or bridges of chain 1 are labelled, with kissing loops labelled in magenta, A-minor interactions in cyan and other interactions in lime. One interaction, B7 (grey), is not ordered in this cryo-EM map, but residues come in sufficiently close contact that interactions could form. The same interactions, but between different pairs of chains, share the same number. f–i, Selected intramolecular interactions as labelled in d,e. j–o, Intermolecular interactions as labelled in e. The sharpened cryo-EM map is displayed at the following contours: 6σ (b,d,e), 8σ (o), 16σ (g,i–n) and 20σ (f,h).
