Figure 4.
Native Assembly of the Ribonucleoproteins (RNPs)
(A) 2D class averages of RNPs reveal two distinct types of RNP ultrastructure: hexameric (boxed in orange) and tetrahedral (boxed in red) assembly.
(B) 3D reconstruction and 2D slices of the RNP. Resolution, 13.1 Å; threshold, 1.0.
(C) Ultrastructure of the RNP hexon and tetrahedron assemblies. Seven RNPs are packed against the viral envelope (gray), forming an “eggs in a nest”-shaped hexagonal assembly (top). Four RNPs are packed as a membrane-free tetrahedral assembly (bottom), most of which were found in the virus away from the envelope. The structural features of the RNPs on the assembly are smeared because of the symmetry mismatch between individual RNPs and the assembly.
(D) Representative projection of RNP hexons assembling into a spherical virus and tetrahedrons into an ellipsoidal virus.
(E) Statistics of the ratio of tetrahedron/hexon assembly reveals that spherical and ellipsoidal virions are more likely to be packed with hexons and tetrahedrons, respectively. The ratio is estimated by sorting 382 virions that have over 5 RNP assemblies by their ratio of long/short axis and counting their ratio of tetrahedron to hexon RNPs. A boxplot shows the minimum, first quartile, medium, third quartile, and maximum of the data.