VPg uridylylation reactions contained cognate VPg-oriI pairs from PV (A), CVB3 (B), or HRV14 (C). The source of 3C and 3Dpol is as indicated. Shown is a representative phosphor image of the VPg-pU(pU) products. Quantifications of UMP incorporation are indicated under each lane (μM VPg-pU(pU) in 30 min). The S.E. value of the measurement did not exceed 20%. Reactions were performed in buffer (50 mM HEPES, pH 7.5, 5 mM magnesium acetate, 10 mM β-ME, 10% glycerol, 10 μM UTP, and 0.04 μM [α-32P]UTP (6000 Ci/mmol)) at 30 °C for 30 min using 3D (1 μM for PV and CVB3, 10 μM for HRV14), 3C (1 μM), VPg (10 μM), and oriI (1 μM).