Figure 1
Schematic representation of the hemoglobin quaternary structure with four globular sub-units (yellow color: α1, α2, β1, β2) and four heme groups (blue color).
(Left) T-form, where the access to the oxygen binding sites of the heme groups is restricted and the overall structure is more compact; (Right) R-form with easier access to the heme groups by oxygen molecule O2 and a more loose structure. The cooperativity of hemoglobin during oxygen binding is related to the transition from the T form to the R form.
