TABLE 3.

Steady-state constants of wild-type and S282T NS5B polymerases for RNA templates during initiation^a

NS5B polymerase	Nucleotide	Km (μM)	Vmax (s−1)	Vmax/Km (s−1/μM)	Efficiency decrease (fold)
WT	CTP	13 ± 4	12 × 10−3 ± 7 × 10−3	0.92 × 10−3
	GTP	9.97 ± 0.9	11 × 10−3 ± 0.3 × 10−3	1 × 10−3
	ATP	46 ± 7	38 × 10−3 ± 1.6 × 10−3	0.82 × 10−3
S282T mutant	CTP	7 ± 1	2.5 × 10−3 ± 0.07 × 10−3	0.35 × 10−3	2.6
	GTP	7.46 ± 3.5	3.1 × 10−3 ± 0.3 × 10−3	0.415 × 10−3	2.4
	ATP	11 ± 3	6.2 × 10−3 ± 0.3 × 10−3	0.56 × 10−3	1.46

^aThe efficiency decrease was determined as the ratio (V_max/K_m)_WT/(V_max/K_m)_mutant. K_m and V_max were calculated as described in Materials and Methods. V_max is expressed in pmol s⁻¹ · pmol⁻¹ enzyme.