Table 1.

Equilibrium dimer stability and operator binding

Protein	Ku, M	ΔΔGu, kcal/mol	K2, M2	ΔΔGd, kcal/mol
Arc	7.0  ×  10−8	0.0	1.5  ×  10−23	0.0
FV10	1.0  ×  10−7	0.2	2.0  ×  10−19	5.6
FY10	1.9  ×  10−7	0.6	6.0  ×  10−20	4.9
FH10	3.8  ×  10−7	1.0	8.0  ×  10−22	2.3

K_u is the equilibrium constant for dimer dissociation and unfolding (A₂ ⇌ 2U) at 25°C, pH 7.5, 100 mM KCl, 0.2 mM EDTA calculated from urea denaturation experiments. ΔΔG_u = −RT ln(K_u−mut/K_u−wt). K₂ is the equilibrium constant for dissociation of the A₄O operator complex to free dimers and operator (A₄O ⇌ 2A₂ + O). ΔΔG_d = −RT ln(K_2−mut/K_2−wt).