The effect of 2,3-diphosphoglycerate on the solubility of deoxyhemoglobin S.
Although highly charged polyanions, such as inositol hexaphosphate, have been clearly shown to decrease the solubility of deoxyhemoglobin S, the effect of 2,3-diphosphoglycerate (DPG), the endogenous allosteric effector within the red cell, has been more controversial. In this work we have compared the effect of DPG on the solubility of native deoxyhemoglobin S and a derivative in which the DPG binding site is blocked by cross-linking the two beta 82 lysine residues. At pH 6.6 and 30 degrees C the solubility of deoxyhemoglobin S was found to be decreased by 15% (i.e., from 18.8 to 16.0 g/dl) in the presence of saturating concentrations of DPG. Under the same conditions DPG had no effect on the solubility of the cross-linked derivative. This result establishes unequivocally that the binding of DPG within the beta cleft directly facilitates the polymerization of deoxyhemoglobin S. Under physiological conditions, the solubility of deoxyhemoglobin S was found to be decreased by 6% in the presence of an equimolar concentration of DPG. A solubility decrease of this magnitude is sufficient to enhance the tendency of SS cells to sickle and may exacerbate the clinical symptoms of sickle cell disease.
D019794:2,3-Diphosphoglycerate; D000755:Anemia, Sickle Cell / Q000097:blood; D001665:Binding Sites; D004163:Diphosphoglyceric Acids / Q000097:blood / Q000494:pharmacology*; D006451:Hemoglobin, Sickle / Q000378:metabolism; D006801:Humans; D011485:Protein Binding; D012995:Solubility
D004163:Diphosphoglyceric Acids; D006451:Hemoglobin, Sickle; D019794:2,3-Diphosphoglycerate