The structure of goat hemoglobins: III. Hemoglobin D, a β chain variant with one apparent amino acid substitution (21 Asp → His)

Abstract

The discovery of a third hemoglobin type, hemoglobin D, in the domestic goat is reported. Comparison of the amino acid compositions of the tryptic peptides of the β-D chain with those of corresponding peptides of the β chains of hemoglobin A revealed the presence of one structural difference, namely, the replacement of an aspartyl residue by a histidinyl residue in peptide T-3b. Edman degradation in this peptide located the substitution in the second position of this peptide which corresponds with position 21 of the total β chain. Both hemoglobins A and D were replaced by hemoglobin C in the AD goat when subjected to experimental anemia. These results were interpreted as indicative that the β-D structural gene arose from the β-A structural gene by mutation after the divergence of the β-A and β-C structural genes.