OXYGEN EQUILIBRIA OF HALF CYANOMET HYBRIDS OF HUMAN AND CANINE HAEMOGLOBINS

By use of acid hybridization techniques, special hybrid molecules were produced between human adult and canine haemoglobins, in which either one of the species of the constituent subunits was fixed specifically in cyanomet form and consequently deprived of its oxygenation function. These molecules were characterized by increased affinity toward oxygen and complete absence of haemhaem interaction (Hill's exponent = 1.0). The latter finding is clearly in contrast with the higher n-value (1.9 or so) of human haemoglobin randomly oxidized by 50%. The bulk of the oxygen Bohr effect on the alkaline side was well preserved although its extent was more or less reduced. The molecules of comparable subunit composition, irrespective of which species of subunit was inactivated, were found to have comparable behaviour in their general oxygenation properties. Similar results were also obtained in the oxidation kinetics of the hybrids with ferricyanide at pH 5.9. Determination of the reactive SH groups of the hybrid haemoglobins suggested that both α- and β-subunits in canine haemoglobin might have one reactive and one unreactive SH group per chain. © 1968.