FIG. 8.
Proposed model of the uridylylation complex. (a) Several poliovirus 3Dpol residues appear to stabilize VPg (red) in its putative binding pocket. Lys172 and Arg179 (green) are critical for stabilizing Tyr3 of VPg in the active site. Residues in blue and red correspond to residues of FMDV that position VPg in its binding pocket. (b) The D-D and D-C interfaces may be responsible for stabilizing interactions between 3BC(D) (yellow and red) and a 3D polymerase molecule (green). VPg (red) has been modeled into the 3D domain using the FMDV-VPg structure as a template (12). These binding interactions might be relevant to the stimulation of VPg uridylylation by either 3C or 3CD or to the binding of uncleaved 3BC or 3BCD as substrates for uridylylation.