Some of the conformational changes required for infectivity and involved in the control of capsid stability and neurovirulence in mice may occur in the vicinity of the fivefold axis of the poliovirus, where there are significant structural differences among the three poliovirus serotypes in the surface exposed loops of VP1 (BC, DE, and HI). A surface depression is located at the fivefold axis of PV2L that is not present in the other two poliovirus serotypes. The observed interaction of RNA with VP4 supports the observation that loss of VP4 ultimately leads to the loss of viral RNA. A model is proposed that suggests dual involvement of the virion fivefold and pseudo-threefold axes in receptor-mediated initiation of infection by picornaviruses.

CRYSTALLOGRAPHY OF BIOLOGICAL MACROMOLECULES protmding quite prominently, fmming deep valleys at the pseudothreefold axes between the A, B, and C subunits. The quasiequivalent A, B, and C subunits adopt the jellyroll fold and are very similar in structure. TheN termini, which had been found on the outside of the viii on immunogenically, are found in the interior of the virion, and the first 26 residues of the A subunit are disordered. The N termini of the B and C subunits, which are completely visible, interact at the intetior of the pseudo 6-fold axes, forming annuli. The C termini are exterior to the viii on. All three histidin~s present in the coat protein are found on the inside of the viiion, and may confirm the prediction that these residues bind RNA.

No abstract