Activity of mutant FMDV polymerases (3D)^a.

aProcedures for the expression and purification of wild type and mutant 3Ds and the assays used have been previously described [27], [50], [63], [65], [67], and are detailed in Materials and Methods. bPoly(rU) synthesis is calculated as pmol UTP incorporated per µg of enzyme per min. cVPg uridylylation activity is calculated as pmol UTP incorporated into VPg per µg of enzyme per min. dRNA binding is calculated as % of RNA template-primer retarded by 1.8 µM enzyme at 10 min reaction time, by dividing the labelled bound (retarded) product by the total labelled RNA and multiplying by 100. The relative amount of labeled RNA was visualized and quantitated with a Phosphorimager (BAS-1500; Fuji).