Figure 3.
Detailed structure of the hemin-binding site in HSA and comparison with myoglobin (a) Side-view of subdomain IB of HSA indicating the comparative binding configurations of hemin (grey carbon atoms) and myristate (yellow carbon atoms). Helices 8–10 are labelled h8-h10. The structures of HSA-hemin-myristate and HSA-myristate [9] were superposed using the Cα atoms of subdomain IB (residues 107–196). The myristate lies along the upper hydrophobic surface of the D-shaped cavity that accommodates hemin. Note that R117, which serves to coordinate the carboxylate group of myristate, is not involved in this function for hemin. (b) Close-up view of the hemin-binding pocket in subdomain IB. The propionate groups of hemin are co-ordinated by R114, H146 and K190. (c) Close-up view of the heme-binding pocket of sperm-whale myoglobin (PDB ID: 4 mbn). Electrostatic interactions between protein side-chains and hemin are indicated by dashed cyan lines. This figure was prepared using Molscript [34] and Pymol [35].