Description of hemoglobin oxygenation under universal solution conditions by a global allostery model with a single adjustable parameter Original Research Article

The Monod–Wyman–Changeux allosteric model parameters evaluated from accurate oxygen equilibrium curves (OECs) of hemoglobin that were measured in an extremely wide range of structural constraints, imposed by allosteric effectors, yielded a closed circle when log KT and log KR were plotted against log L0 and log L4, respectively, showing novel phenomena that L0 and L4 have a maximal value and a minimal value, respectively, and KT and KR vary by more than three orders of magnitude. These phenomena were successfully described by a global allostery model, which mathematically keeps the frame work of the MWC model, but allows that KT under a set of solution conditions becomes larger than KR under another set of solution conditions and postulates that a representative allosteric effector binds to both the T and R states with a lower affinity but with a larger stoichiometry for the R state than for the T state. Thus, this global model can describe any given OEC measured under universal solution conditions with the single adjustable parameter, the concentration of the representative effector.