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Figure 7<br />

HRV14 VP1 hydrophobic pocket schematic with WIN 61605<br />

illustrating some of the terminology commonly used to describe<br />

this pocket. Notice the GH loop separates the pocket from the<br />

canyon floor.<br />

Page 500<br />

lished data). These pockets all share similar features and have been described as foot shaped, with a<br />

hydrophobic toe region, a heel region capable of hydrogen bonding, and a pore region near the ankle of<br />

the foot (Figure 7).<br />

Many of the picornavirus structures have been shown to have electron density in their VP1 pockets even<br />

in the absence of any added drug. These densities have been modeled as fatty acids or similar<br />

compounds [12,15,56,70–72]. The occurrence of these pocket factors have led some to hypothesize that<br />

these factors perform a similar function as do capsid-binding inhibitors, that is, to stabilize the virions<br />

[15,24,41,73,74].<br />

Teleologically one could argue that the virion would pick up a fatty acid in its VP1 pocket before its<br />

egress from the cell, which would then stabilize the virion in transit to new hosts. The HRVs are known<br />

to be stable for long periods of time on surfaces and the dominant mode of transmission is thought to be<br />

hand-to-hand contact [75,76]. When a new host cell is reached, the stabilization factor might exit the<br />

pocket. This would allow the necessary conformational transition (probably at the GH loop) to occur and<br />

allow productive uncoating.<br />

A. Multiple Targets<br />

The use of these structures in a traditional structure-<strong>based</strong> drug design approach has been limited <strong>by</strong> the<br />

large number of unknown target serotype structures. There have been useful studies that have grouped<br />

picornaviruses <strong>based</strong> on their susceptibility to various antiviral agents (see below) [7,77]. However, in<br />

order to design a truly broad-spectrum single drug, the structural elements common among many<br />

serotypes must be considered.<br />

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