Figure 2.

Influence of fatty acids on HSA structure and zinc binding. (A). X-ray crystal structure of HSA with zinc bound (PDB: 5IJF). Zinc binds in a tetrahedral geometry at site A involving the side chains of His67, His247, and Asp249. (B). X-ray crystal structure of HSA with myristate bound (PDB: 1BJ5). The binding of myristate at the FA2 site causes movement of zinc-binding residue His67 away from His247 and Asp249. (C). Isothermal titration calorimetry showing the effect of fatty acid loading on zinc binding to HSA. In the experiments 1.5 mM ZnCl₂ was titrated into 60 µM HSA, in the presence of either 0 (black), 3 (blue), 4 (green), or 5 (red) mol. eq. of myristate in a buffer containing 50 mM Tris, 140 mM NaCl, pH 7.4. (D). Bar chart representing the availability of binding site A in the presence of 4 mol. eq. of various fatty acids. All except octanoate had large effects on Zn²⁺ binding to the protein. Data for parts C and D were taken from Sobczak et al. [88].