Figure 2
From: Iron and bismuth bound human serum transferrin reveals a partially-opened conformation in the N-lobe
(a) Superimposition of the N-lobe of Fe-hTF/2N (“fully-closed” conformation), FeNFeC-hTF (“partially-opened” conformation), BiNFeC-hTF (“partially-opened” conformation) and apo-hTF (“fully-opened” conformation).The N2-subdomains of the four proteins are superimposed and represented as Cα in gray, while the N1-subdomains are shown as ribbon models with apo-hTF in pale green, FeNFeC-hTF in salmon, BiNFeC-hTF in purple and Fe-hTF/2N in light blue. Strands β3 that directly connect to residues Asp63 (hexagonal prism) are highlighted in darker color in each structure. Fe(III) ions are shown as red and blue spheres in FeNFeC-hTF and Fe-hTF/2N, respectively. Bi(III) is shown as purple sphere in BiNFeC-hTF. (b) Position shifts of the key residues in the metal binding center of the N-lobe upon metal binding and dissociation. Coordination residues in Fe-hTF/2N are shown as stick models in blue, while the corresponding residues in FeNFeC-hTF, BiNFeC-hTF and apo-hTF are shown as stick models in red, purple and green, respectively. (c) Molecular surface presentations of the N-lobes in apo-hTF, BiNFeC-hTF, FeNFeC-hTF and Fe-hTF/2N. A schematic diagram shows the opening extent of N-lobe in the structures of FeNFeC-hTF (red), BiNFeC-hTF (purple) and apo-hTF (green) relative to the Fe-hTF/2N (blue).
