Table 6.

Experimentally determined parameters for Fe²⁺ (Zn²⁺ and Tb³⁺) binding to HuHF and EcFtnA. The ITC data is collected under anaerobic conditions using 50–100 mM Mops buffer, 50–100 mM NaCl, and 1 mM Na₂S₂O₄ at pH 7 and 25.00 °C. The reported thermodynamic quantities are apparent values and include the contributions to the overall equilibrium from ferritin and buffer species in different states of protonation. Standard errors from replicate determinations are indicated. Only values for the strong sites are reported.

Apo-protein	n	KITC (M−1)	ΔHITC (kJ/mol)	ΔS (J/K.mol)	ΔG (kJ/mol)
HuHF + Fe2+	25.03 ± 1.05	(1.48 ± 0.41) × 105	− 8.19 ± 0.12	126.44 ± 0.73	− 29.51 ± 0.72
HuHF + Zn2+	n1 = 6.9 ± 0.2 n2 = 90.7±29.5	K1 = (5.9 ± 1.7) × 106 K2 = (3.1 ± 0.6) × 104	ΔH1 = −13.5 ± 0.5 ΔH2 = 22.1 ± 5.5	ΔS1 = 84.5 ± 0.9 ΔS2 = 160.1 ± 5.5	ΔG1 = − 38.7 ± 0.7 ΔG2 = − 25.6 ± 0.5
HuHF + Tb3+	n1 = 8.7 ± 0.5 n2 = 87.3 ± 2.4	K1 = (6.2 ± 2.5) × 106 K2 = (6.7 ± 1.1) × 104	ΔH1 = 4.5 ± 0.9 ΔH2 = 25.4 ± 1.2	ΔS1 = 145.1 ± 1.4 ΔS2 = 177.6 ± 1.3	ΔG1 = − 38.7 ± 1.1 ΔG2 = − 27.5 ± 0.4
EcFtnA + Fe2+	n1 = 21.1 ± 0.5 n2 = 19.8± 0.7	K1 = (3.5 ± 0.8) × 106 K2 = (1.8 ± 0.4) × 105	ΔH1 = 3.4 ± 0.2 ΔH2 = 9.9 ± 0.3	ΔS1 = 136.5 ± 2.1 ΔS2 = 133.8 ± 2.2	ΔG1 = − 37.3 ± 0.6 ΔG2 = − 30.0 ± 0.6
EcFtnA + Zn2+	n1 = 4.2 ± 1.2 n2 = 22.1± 0.5 n3 = 27.7± 0.8	K1 = (1.0 ± 0.1) × 107 K2 = (3.7 ± 0.2) × 106 K3 = (9.6 ± 0.8) × 103	ΔH1 = 1.2 ± 0.7 ΔH2 = −24.4 ± 0.2 ΔH3 = 47.9 ± 1.3	ΔS1 = 138.2 ± 2.5 ΔS2 = 44.0 ± 0.7 ΔS3 = 236.9 ± 1.6	ΔG1 = − 40.0 ± 0.2 ΔG2 = − 37.5 ± 0.1 ΔG3 = − 22.7 ± 0.2