TABLE 4.

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

NS5B polymerase	Nucleotide	Km (μM)	Vmax (s−1)	Vmax/Km (s−1/μM)	Efficiency decrease (fold)
WT	CTP	12 ± 4	68 × 10−3 ± 3 × 10−3	5.2 × 10−3
	GTP	63 ± 19	6.2 × 10−3 ± 0.7 × 10−3	0.1 × 10−3
	ATP	41 ± 7	7.5 × 10−3 ± 0.4 × 10−3	0.2 × 10−3
S282T mutant	CTP	23 ± 9	25 × 10−3 ± 3 × 10−3	1 × 10−3	5.2
	GTP	ND	ND	0.01 × 10−3	10
	ATP	ND	ND	0.01 × 10−3	20

^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. ND, not detectable.