Table I.

Observed catalytic efficiencies (k_pol/K_d) and resulting TS binding free energies (ΔG^TS_bind,obs).^a

Pol β variant	A:T		G:C
	kpol/Kd [M-1s-1]	ΔGTSbind,obs [kcal/mol]	kpol/Kd [M-1s-1]	ΔGTSbind,obs [kcal/mol]
wild type	4,100,000	-14.6	6,600,000	-14.9
R149A	685,000	-13.5	920,000	-13.7
R183A	43,000	-11.8	440,000	-13.2
K280A	n.a.b	n.a.b	2,000,000	-14.1
Pol β variant	A:C		G:T
	kpol/Kd [M-1s-1]	ΔGTSbind,obs [kcal/mol]	kpol/Kd [M-1s-1]	ΔGTSbind,obs [kcal/mol]
wild type	1,200	-9.6	570	-9.1
R149A	312	-8.7	n.a.b	n.a.b
R183A	14.6	-6.8	2.6	-5.8
K280A	n.a.b	n.a.b	220	-8.5

^aThe pre-steady state experiments for the incorporation of T or C opposite A (A:T and A:C) or G (G:T and G:C) were all conducted in the same laboratory under the same conditions, allowing for a consistent set of data.¹⁷ Binding free energies were calculated using Equation 1; the rate constant for the reference reaction in water (k_water = 2.8 × 10^-4 M^-1s^-1) was taken from Reference 42.

^bn.a., not available.