TABLE 1.

Kinetic constant values from FP-based ERα_DBD-Ext- and Sox2_HMG-binding experiments

Protein	Ligand	$\text{[math]}$ (nM)	n (Hill)	$\text{[math]}$ (M⁻¹s⁻¹)	$\text{[math]}$ (×10⁻² sec⁻¹)	$\text{[math]}$ (×10⁻⁴ sec⁻¹)
ERα_DBD-Ext	ERE dsDNA	11 ± 2.1	2.1 ± 0.30	5.8 ± 3.1 × 10⁴	4.7 (71%)	7.3 (29%)
	ΔERE dsDNA	2.8 ± 0.6^a	1.5 ± 0.22^a	8.7 ± 4.6 × 10⁴	8.9 ± 4.4 (60%)	5.9 ± 1.1 (40%)
	XBP1 hRNA	370	0.91	14 × 10⁴	5.6 ± 2.7 (64%)	6.6 ± 1.2 (36%)
Sox2_HMG	CBS dsDNA	≤1 (54%), 420 ± 120^b	n/a^b	0.75 × 10⁶	5.0 ± 2.3 (67%)	13 ± 2.1 (33%)
	G4 RNA	≤1 (44%), 110 ± 32^b	n/a^b	1.1 × 10⁶	5.4 (73%)	9.6 (27%)
	NBS dsDNA	29 ± 9.1	0.57 ± 0.06	n.d.	n.d.	n.d.
	hRNA	53 ± 16	1.1 ± 0.21	n.d.	n.d.	n.d.
	poly(A) RNA	40 ± 13	0.68 ± 0.11	n.d.	n.d.	n.d.

The table includes apparent equilibrium dissociation constants ( $\text{[math]}$ ) and Hill coefficients (n) from Figure 1 (fit with Equations 1 and 2), apparent initial association rate constants ( $\text{[math]}$ ) from Figure 4, and apparent dissociation rate constants ( $\text{[math]}$ ) from Figure 2 (fit with Equation 5). Values are mean ± ½ range (across two to three independent experiments). Values without error are based on a single experiment. For $\text{[math]}$ , values in parentheses are the percent signal contributions of the first transitions in two-transition binding regression, and for $\text{[math]}$ , values in parentheses are the percent contributions of the fast or slow components in biexponential regression. Percentages are the averages across two to three independent experiments, or values from a single experiment if the associated rate constants have no error.
(n/a) Not applicable, (n.d.) not determined.
^a $\text{[math]}$ is close to ligand concentration; it is possible that K_d < $\text{[math]}$ and n (Hill coefficient) are artificially inflated.
^bBinding curves were fit with a two-transition equation, not the Hill equation.

Transcription factors ERα and Sox2 have differing multiphasic DNA- and RNA-binding mechanisms