FIGURE 4.

Effects of changing ferritin ion exit and entry channel residues on Fe²⁺ exit from eukaryotic ferritin protein cages. Progress curves for the surface-limited reduction and dissolution of protein-caged ferric minerals and Fe²⁺ exit from the protein cages of wild-type, M-R72D, M-R122D, and M-L134P ferritins. The Fe²⁺ release reaction was initiated by mixing solutions of mineralized ferritin with a solution of 2.5 mm FMN, NADH, and bipyridyl and monitoring Fe²⁺-(bipyridyl)₃ outside the protein cages. (numerical rates are shown in supplemental Table S2). Data are representative of two independent protein preparations, with 3–4 repetitions for each. Black, M-WT; green, M-L134P; red, M-R72D; blue, M-D122R.