Functional properties of hemoglobin Leiden (α2(A)β2(6 or 7 Glu deleted))
Hemoglobin Leiden is an abnormal human hemoglobin in which a glutamic acid residue was deleted from the β chain at position 6 or 7. The α amino groups of the β chain N termini in tetrameric hemoglobin A are thought to be directly involved in the binding of simple anions and organic phosphates. The deletion of the 4th or 5th residue of the A helix in hemoglobin Leiden shortens the N terminus of the β chain, and the results reported show that the anion binding site is affected. Hemoglobin Leiden shows a decreased response to inorganic phosphate, chloride, 2,3 diphosphoglycerate, and inositol hexaphosphate, both in equilibria and kinetics of ligand binding. Although hemoglobin Leiden shows an altered response to anions, neither the cooperativity of ligand binding nor the Bohr effect are significantly altered by the deletion. The decreased effect of cofactors seems to be due to a decrease in the strength of anion binding which may be attributed to the altered geometry of the anion binding site.
Bonaventura, J; Bonaventura, C; Amiconi, G
Archives of Biochemistry and Biophysics
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