The oxygen equilibrium of the hybrids of canine and human haemoglobin

Hybrids of human A₁ and canine haemoglobins have been prepared, namely Hbα₂^Aβ₂^Ca and Hbα₂^Caß₂^A, and the oxygen equilibria have been studied in comparison with those of the parent molecules. The behaviour of the α₂^Caß₂^A hybrid is similar to that of the parent molecules (which are both much alike), although the reverse Bohr effect is somewhat increased. In contrast the α₂^Aß₂^Ca hybrid has no reverse Bohr effect, lower oxygen affinity (especially at pH<7) and the equilibrium curve is no longer invariant in shape with pH. It is notable that the normal (or alkaline) Bohr effect is the same for all four molecules. These results emphasize the basic structural similarity of the haemoglobin chains from different species but also point to the specificity of the interaction between the α and β chains from the different haemoglobins.