Table 3.

Operator and nonoperator DNA binding

	Kd calf-thymus DNA	Kd operator-subsite DNA
Wild type	8.7  ±  3.6⋅10−8 M	1.2  ±  0.6⋅10−11 M
FV10	3.3  ±  1.0⋅10−7 M	1.7  ±  0.4⋅10−8 M
ΔΔGd	0.8  ±  0.4 kcal/mol	4.2  ±  2.4 kcal/mol

K_d values are the average of three independent experiments (±SD) for experiments performed at 25°C, pH 7.5, and 100 mM KCl. The equilibrium constants for nonspecific DNA are microscopic constants for dissociation of an Arc dimer from a single nonspecific site. The equilibrium constants for arc operator DNA are for dissociation of an Arc dimer from a single subsite (for the sequence of the 22-bp subsite DNA, see ref. 14. ΔΔG_d = −RT ln(K_d−wt/K_d−FV10).