Role of subunit interfaces in the allosteric mechanism of hemoglobin.

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Abstract
The surface area buried in subunit interfaces of human deoxyHb and of horse metHb was calculated. A larger surface area is buried in deoxy- than in metHb as a result of tertiary and quaternary structure changes. In both molecules the dimer-dimer interface is close-packed. This implies that hydrophobicity stabilizes the deoxystructure, the free energy spent in keeping the subunits in a low-affinity conformation being compensated by hydrophobic free energy due to the smaller surface area accessible to solvent.