Structure and Functions of Fetal Hemoglobin

The fetal hemoglobin (HbF) of man and most other mammals, like HbA, is a tetramer composed of two subunits. The two a polypeptide chains which it incorporates are identical with the a polypeptide chains of HbA and they are controlled by the same gene, which is active throughout life (Baglioni et al., 1961 Minnich et al., 1962). The two other polypeptide chains differ from the chains of HbA and have been called y chains. 

The difference between the amino acid composition of HbF and HbA was established several years ago (Huisman, 1954 Dustin et al., 1954). Since the identity of the a chains of HbF and HbA was subsequently demonstrated (Hunt, 1959 Schroeder et al., 1961, 1963a), the differences between them are localized entirely in the y and p chains. In work which continued over many years, Schroeder and co-workers (1961, 1963b) established the sequence of all 146 amino acid residues of the 7 polypeptide of hemoglobin and compared it with the polypeptide sequence of the P chain, also containing 146 residues. They found differences in the position of 17 amino acid residues in the a and p chains, giving rise to 39 different sequences. The p and 7 chains differed in the overall balance between acid and basic amino acids, and finally, the 7 chain has two supplementary histidine residues. 

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