TABLE 3.

Metal binding to FetP (34.3 μm) as determined by ITC

Conditionsa	Metal titrated	n	Kd	ΔH	ΔS	ΔG
			μm	kcal/mol	cal/mol/K	kcal/mol
BisTris	Cu2+	0.915	4.1	−2.18	+17.3	−7.33
BisTris, 27.4 μm Mn2+	Cu2+	(1.0)b	69.4	−1.52	+13.9	−5.66
BisTris, 160 μm Zn2+	Cu2+	NBc	NB	NB	NB	NB
BisTris	Mn2+	0.404	0.6	−3.82	+15.5	−8.44
BisTris, 94 μm Cu2+	Mn2+	PEd	PE	PE	PE	PE
BisTris, 160 μm Zn2+	Mn2+	0.372	10.9	−3.49	+11	−6.77
BisTris	Zn2+	NB	NB	NB	NB	NB
ACES	Zn2+	1.4	15.2	+2.27	+29.6	−6.55
ACES, 34.3 μm Mn2+	Zn2+	(1.0)b	348	+8.89	+45.6	−4.70
ACES, 34.3 μm Mn2+	Zn2+	(1.5)b	303	+5.48	+34.5	−4.80
ACES, 94 μm Cu2+	Zn2+	NB	NB	NB	NB	NB
ACES	Mn2+	0.426	3.6	−4.66	+9.27	−7.42
ACES, 160 μm Zn2+	Mn2+	0.548	14.4	−9.37	−9.3	−6.60
ACES, 94 μm Cu2+	Mn2+	0.435	45	−22.0	−46.1	−8.26
ACES	Cu2+	NB	NB	NB	NB	NB

^a 25 mm buffer, pH 7.2.

^b n assumed in the modeling to allow calculation of the other values.

^c NB, no binding was observed.

^d PE, positive enthalpy. ΔH of about +1 kcal/mol, but the data could not be used in binding site models to calculate discrete values for K_d.