Table 3.

Kinetic Constants for Nucleotide Incorporation by FMDV 3Dwt and 3D(V173I)

RNA Substratea	NTPb	3Dwt				3D(V173I)
		Kd,NTP (µM)c	kpol (s−1)d	kpol/Kd,NTP (µM−1 s−1)e	$\frac{\mathit{(k}pol/K_d,NTP)NTP}{\mathit{(k}pol/K_d,iNTP)iNTP}$f	Kd,NTP (µM)c	kpol (s−1)d	kpol/Kd,NTP (µM−1 s−1)e	$\frac{\mathit{(k}pol/K_d,NTP)NTP}{\mathit{(k}pol/K_d,iNTP)iNTP}$f
Sym/sub-AU	A	44 ± 7	255 ± 44	5.8 ± 1.4	9.8 × 104	60 ± 46	88 ± 14	1.5 ± 1.1	9.1 × 104
	G	214 ± 71	12.6 ± 1.4 (× 10−3)	5.9 ± 2.1 (× 10−5)		635 ± 109	10.3 ± 0.8 (× 10−3)	1.6 ± 0.3 (× 10−5)
Sym/sub-UA	U	54 ± 25	218 ± 27	4.0 ± 1.9	1.0	51 ± 9	196 ± 9	3.8 ± 0.7	3.2
	FU	36 ± 12	148 ± 8	4.1 ± 1.4		90 ± 36	108 ± 12	1.2 ± 0.5
Sym/sub-UG	C	15 ± 6	307 ± 26	20.3 ± 8.9		20 ± 8	283 ± 23	14.4 ± 5.7
	FU	24 ± 6	13.9 ± 0.7 (× 10−3)	5.8 ± 1.4 (× 10−4)	3.5 × 104	30 ± 15	9.7 ± 1.1 (× 10−3)	3.3 ± 1.7 (× 10−4)	4.4 × 104
	U	93 ± 38	9.7 ± 1.1 (× 10−3)	1.0 ± 0.4 (× 10−4)	2.0 × 105	125 ± 20	4.2 ± 0.2 (× 10−3)	3.4 ± 0.6 (× 10−5)	4.2 × 105
Sym/sub-FuG	A	273 ± 55	137 ± 10	0.50 ± 0.11	3.5 × 102	29 ± 4	165 ± 6	5.69 ± 0.81	49.0 × 102
	G	107 ± 28	0.16 ± 0.01	1.45 ± 0.40 (× 10−3)		130 ± 31	0.15 ± 0.01	1.16 ± 0.29 (× 10−3)

^aSymmetrical substrates (sym/subs) used in the assays depicted in fig. 2 and supplementary figure S5, Supplementary Material online.

^bNucleotidic substrate used as a triphosphate for incorporation at the second position of the sym/sub; the exception is sym/sub-FuG for which incorporation was measured at the first position.

^cK_d,NTP, dissociation constant for NTP binding.

^dk_pol, optimal polymerization rate constant.

^ek_pol/K_d,NTP, catalytic efficiency.

^f(k_pol/K_d,NTP)_NTP/(k_pol/K_d,iNTP)_iNTP, selectivity for discrimination in favor of incorporating the cognate nucleotide (NTP) instead of the incorrect nucleotide (iNTP).