Anions interlocking sites model

From a stereochemical analysis of binding anions, the interlocking-sites model is most consistent with available data. We have approached the question of the spatial relationship of metal ion and anion in human transferrin through electron and nuclear magnetic resonance spectroscopy (17,49). 

Fig. 25. A schematic representation of the interlocking sites model for the binding of anions to transferrins. From Schlabach and Bates (178), with permission.

Figure 19. A model for the anion- and iron-binding sites of transferrin depicted assuming an interlocking-site hypothesis. The protein furnishes five ligands to the metal in the iron binding site three tyrosines and two histidines. The carbonate ion binds to an arginine in the anion-binding site and functions as a sixth ligand to the metal center. The carbonate forms a bridge between the metal- and the anion-binding sites in the active center (36).

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