Binding of the antiviral drug WIN51711 to the sabin strain of type 3 poliovirus: structural comparison with drug binding in rhinovirus 14.

The crystal structure of the Sabin strain of type 3 poliovirus (P3/Sabin) complexed with the antiviral drug WIN51711 has been determined at 2.9 A resolution. Drugs of this kind are known to inhibit the uncoating of the virus during infection, by stabilizing the capsid against receptor-induced conformational changes. The electron density for the bound drug is very well defined so that its position and orientation are unambiguous. The drug binds in a nearly extended conformation, slightly bent in the middle, in a blind pocket formed predominantly by hydrophobic residues in the core of the beta-barrel of capsid protein VP1. Comparisons between this structure, the corresponding drug complex in human rhinovirus 14 (HRV 14), and the native structures of both viruses demonstrate that the binding of WIN51711 has markedly different effects on the structures of these two viruses. Unlike HRV14, wherein large conformational changes are observed in the coat protein after drug binding, the binding of this drug in poliovirus does not induce any significant conformational changes in the structure of the capsid protein, though the drug has a greater inhibitory effect in P3/Sabin than in HRV14. The implications of this result for the mechanism of capsid stabilization are discussed.