A 1H NMR comparative study of human adult and fetal hemoglobins

The affinities of the individual subunits in human adult and fetal hemoglobins to azide ion have been determined from the combined analysis of NMR and optical titration data. Structural and functional non-equivalence of the constituent subunits, i.e. alpha and beta subunits in human adult hemoglobin and alpha and gamma subunits in human fetal hemoglobin, has been confirmed. The function of the alpha subunits, which are common to both hemoglobins, is essentially identical in these hemoglobins and, in spite of the substitutions of 39 amino acid residues between beta and gamma subunits, they exhibit similar azide ion affinities. The present study also demonstrates that the NMR spectral comparison between the two proteins provides signal assignments to the individual subunits in intact tetramer.