Table II.

SPR Derived Binding Constants for MexR-wt Binding to mexO

DNA Box	Oligomeric State	Ka	X2/R(max)
PIa	Dimer	1.2·107	0.08
PIIa	Dimer	2.7·106	0.05

Predicted association constants (K_a, M) of MexR-wt, PI-, PII-, and PI-PII-DNA, calculated from Biacore measurements. Fits to experimental data are derived using a “two-state reaction conformational change” model where independent fits were made assuming different oligomeric states. The corresponding fits are shown in Figure 2. The goodness of the fit was judged by X²/R_(max), as described in Experimental Procedures. Less accurate fits showed showed X²/R_(max) of 0.1 (PI, monomer, tetramer), 0.15 (PII, monomer), and 0.18 (PII, tetramer) and significant visual discrepancies in the fit.