I have placed the R state and T state of hemoglobin from the Bar-Headed Goose, Anser indicus, in the Gallery. Inositol hexaphosphate is the polyanionic effector of avian hemoglobins and I have included a molecule of inositol hexaphosphate in the polyanion binding site of the T state. The positive charges of the polyanion binding site can be visualised by following the instructions in the Gallery. It can be seen that there are more positive charges than in human hemoglobin. The number of positive charges able to interact with the inositol hexaphosphate is more than appears at first sight, because allowance must be made for the flexibility of lysine side-chains. The larger number of positive charges accords with the fact that the avian effector has more negative charges than does diphosphoglycerate, the effector in human hemoglobin.
The Gallery can be accessed by clicking on the Title of this Post.
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