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

Abstract

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. α and β subunits in human adult hemoglobin and α and γ subunits in human fetal hemoglobin, has been confirmed. The function of the α 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 β and γ 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.