Unequivalence between hemoglobin subunits. The effects of inositol hexakisphosphate on the absorption spectrum of liganded valency hybrids.

The effects of inositol hexakisphosphate on the visible absorption spectrum of liganded valency hybrids alphaCO2 beta+H20, alpha+H2ObetaCO2 and alphaCO2beta+CN2, alpha+CN2beta CO2 (where alphaCO, alpha+H2O, alpha+CN and betaCO, beta+H2O, beta+CN represent the alpha and beta chain of hemoglobin, respectively, in their carbon monoxide, aquomet and cyanomet forms) have been examined in an attempt to determine if their alpha and beta chains are equally sensitive to the action of the anion. The difference spectra induced by inositol hexakisphosphate, are different for the two chains. The beta+H2O subunit contributes chiefly to the absorbance changes, rather than alpha+H2O. In contrast, it is the alphaCO chains which is more sensitive to inositol hexakisphosphate than betaCO. The question of whether such a selective response would also occur in aquomethemoglobin and carboxyhemoglobin is discussed. Criteria of changes in the quaternary structure of hybrids has been studied by measuring the effects of inositol hexakisphosphate on their ultraviolet absorption spectrum.