Description of hemoglobin oxygenation under universal solution conditions by a global allostery model with a single adjustable parameter.
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 K(T) and log K(R) were plotted against log L(0) and log L(4), respectively, showing novel phenomena that L(0) and L(4) have a maximal value and a minimal value, respectively, and K(T) and K(R) 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 K(T) under a set of solution conditions becomes larger than K(R) 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.
Imai
Kiyohiro
K
Department of Physiology and Biosignaling, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan. kimai@phys1.med.osaka-u.ac.jp
Tsuneshige
Antonio
A
Yonetani
Takashi
T
D000494:Allosteric Regulation / Q000502:physiology; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D010100:Oxygen / Q000097:blood* / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D012996:Solutions; D013053:Spectrophotometry / Q000379:methods; D013696:Temperature
D006454:Hemoglobins; D012996:Solutions; D010100:Oxygen