The α globin-AHSP and α₁β₁ interfaces. The structure was taken from Feng et al⁹  (PDB 1z8u), and the drawings were made in PyMol. (A) Space-filling model of the α globin-AHSP interaction with α globin depicted in silver and AHSP in teal. The key α globin residues K99, AHSP D29, and AHSP Q25 are shown as sticks with Corey-Pauling-Koltun (CPK) coloring. (B) Ribbon drawing of the α globin-AHSP interface. The amino acids that were mutated are depicted as sticks with CPK coloring. R31 is not shown because it is on the contralateral faces of the diagrams in panels A and B. The α globin residues under investigation here, except R31 and A130, all contact AHSP. (C) The primary amino acid sequence of human α globin. The triangles show predicted AHSP-binding sites. The circles show residues that come into close contact with β globin at the α₁β₁ interface. The squares show β globin contact sites at the α₁β₂ interface. Amino acids examined by mutational analysis in this study are shaded.