Table 1.

Equilibrium dissociation constants (±SE) for operator binding (K_o) and inducer (IPTG) binding (K_i) of wt tetrameric Lac repressor and the dimeric active mutant 331Stop

	Ko (M)	Ki (M)
In vitro (Oid)/tet. LacR	1.26 (±0.05) × 10−11	8.2 (±0.4) × 10−6
In vivo (O1)/tet. LacR	4.39 (±0.02) × 10−10	6.7 (±0.1) × 10−6
In vivo (O1)/dim. LacR	2.44 (±0.06) × 10−10	6.4 (±0.4) × 10−6

For in vivo operator binding, a Lac repressor dimer concentration of 1 × 10⁻⁷ M is assumed (24). In vivo data are for operator O₁ and in vitro data are for the ideal symmetric lac operator O_id (31,32).