The oxygen Bohr effect in mouse hemoglobin

Abstract

The variat’ion of oxygen affinity with pH-the Bohr Effect--of human and horse hemoglobins has been applied (1, 2) to a model post8ulat8ing two oxygen-linked acid groups per heme, the same for each hcme, one of which is st,rengthened and the other weakened by oxygenation. In the latest application of this model (1) a reasonably satisfactory agreement of the data at different, t,emperatures was obtained by assigning t,o t,he more alkaline of these groups an ionization heat’ suggesting imidazolc, and t’o t’he other, a heat suggesting carboxyl. In both cases this heat was assumed to be the same in the oxygenated and deoxygenated form of the protein. Not long ago, Riggs (3) presented results that would indicat,e that mouse hemoglobin has a considerably larger Bohr effect’ than either horse or human hemoglobin. In view of t(his we have carried out a survey of the oxygen equilibrium of mouse hemoglobin, over a wide range of pH and temperature, to see whether the model is applicable t’o this hemoglobin also, and thus gain additional evidence as to its generality.