Iron uptake in ferritin is blocked by binding of [Cr(TREN)(H2O)(OH)]2+, a slow dissociating model for [Fe(H2O)6]2+ -- Data Supplement - Supporting Table 1 -- Proceedings of the National Academy of Sciences

Supporting information for Barnés et al. (2002) Proc. Natl. Acad. Sci. USA 99 (8), 5195–5200. (10.1073/pnas.032089399)

Table 1.
Cr(TREN) inhibition of oxidation and mineralization and ferritin functional iron sites

Protein		Cr(TREN) binding		Inhibition Fe oxidation %	Fe³⁺ mineralization Cr per protein required to inhibit
Name	Fe sites^†	Sites per ferritin	K _d, mM	One Cr per subunit	50%	>90%
rH	P + N + F_ox	58 (2.4/sub)	0.25	98	60 (2.5/sub)	n.d.
rH-L134P	P* + N + F_ox	68 (2.8/sub)	0.05	97	60 (2.5/sub)	72 (3.0/sub)
HoSF^‡	P + N + 0.15 F_ox	60 (2.5/sub) ^§	0.08	67	43 (1.8/sub)	26 (1.1/sub)
rL	P + N	48 (2.0/sub)	0.16	n.d.	41 (1.7/sub)	72 (3.0/sub)
rL-E2	P	48 (2.0/sub)	0.20	n.d.	21 (0.9/sub)	n.d.

n.d., not determined.

^†Functional Ferritin Fe sites are (1): P, pore or threefold axis channel of subunit trimers; P*, disordered pore (20); F_ox, di-iron ferroxidase site (H subunit specific); N, multi-glutamate nucleation site at the twofold axis of subunit dimers. ^‡Horse spleen ferritin as isolated has an average of 3–4 H type subunits and 20–21 L subunits per molecule or an average of 0.1 to 0.15 F_ox sites per subunit because the Fox site is in H exclusively in H subunits. In contrast, the recombinant ferritins assemble from subunits of only one sequence. ^§An improved fit to the HoSF data was obtained when using a two-site model. The values correspond to K_d1 = 0.006 (n₁ = 1) and K_d2 = 0.12 (n₂ = 2), yielding a total of 72 Cr(TREN) per protein or 3 Cr(TREN) per subunit.