FIG. 4.

Amphipathic hexameric helical bundles found at the quasi-sixfold axes. (A) A stereo view of the electron density at 1 ς and the fitted model at the N termini of the C subunits are shown. The model is colored according to atom type. (B and C) Six helices about the quasi-sixfold axis (Q6). The C-α backbones for the B and C subunits are shown in blue and red, respectively. The side chains of the inner, hydrophobic residues are shown in green. All the residues shown in green are leucine except for the most N-terminal residue, which is a phenylalanine. The view from the capsid toward the RNA interior in panel B is parallel to the icosahedral axis, whereas the view in panel C is perpendicular to the quasi-sixfold axis.