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. Author manuscript; available in PMC: 2014 Mar 26.
Published in final edited form as: Biochemistry. 2013 Mar 15;52(12):10.1021/bi301620x. doi: 10.1021/bi301620x

Figure 1.

Figure 1

Quaternary assembly of human and clam hemoglobins. Subunits are depicted as van der Waals spheres for main chain and heme atoms, with heme groups shown in red, E and F helices in cyan and the rest of the main chain in gray. (a) Human oxygenated HbA (PDB code 1HHO) is shown with α subunits in dark gray and β subunits in light gray. Note how the E and F helices are on the outside of the molecule. (b) Scapharca inaequivalvis tetrameric HbII-CO (PDB code 1SCT) is shown viewed approximately along its molecular dyad with A subunits in dark gray and B subunits in light gray. Note the extensive subunit pairings involving the E and F helices. (c) Scapharca inaequivalvis homodimeric HbI-CO (PDB code 3SDH) viewed approximately along its molecular dyad showing the extensive dimeric interactions involving the E and F helices.