title: The binding of chloride ions to ligated and unligated human hemoglobin and its influence on the Bohr effect.
abstract: The contribution of the interaction of chloride ions with deoxy and oxyhemoglobin to the Bohr effect can be described by a simple binding model. Applying this model to experiment data reveals that at physiological pH and ionic strength about half of the release of Bohr protons is due to a difference in chloride ion binding to deoxy- and oxyhemoglobin. The chloride-independent part of the Bohr effect corresponds with the shift in pK which His-146 beta shows upon oxygenation. The proton absorptioon by hemoglobin observed upon oxygenation below pH 6 is apparently due to a chloride-ion-induced proton uptake, which is larger for oxyhemoglobin than for deoxyhemoglobin. The analysis of the experimental data indicates the existence of only two oxygen-linked chloride ion binding sites in both deoxy and oxyhemoglobin. In deoxyhemoglobin the binding sites most likely consist of Val-1 alpha of one chain and Arg-141 alpha of the partner chain. The sites in oxyhemoglobin consist of groups with a pK value in the neutral pH range; they do not contain lysyl or arginyl residues.
mesh_terms: D001665:Binding Sites; D002712:Chlorides; D006454:Hemoglobins; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010084:Oxidation-Reduction; D011522:Protons
chemical_list: D002712:Chlorides; D006454:Hemoglobins; D011522:Protons