Hemoglobins of mice: Sequence and possible ambiguity at one position of the alpha chain

The sequences of amino acids in the α chains of hemoglobins from C57BL, BALB/c, and NB mice were studied. C57BL is a common strain of laboratory mice; therefore, it is used as the standard for comparison with others. The α chain of each has 141 amino acids and is homologous to that of man and other vertebrates. When these α chains were compared with that of normal adult human hemoglobin, amino acid exchanges were found at 16 positions. C57BL α chain differs from that of BALB/c at position 68 only, where C57BL consistently has asparagine while BALB/c apparently has two forms, differing only in whether there is serine or threonine inserted in the chain. The insertions of serine or threonine at position 68 occur at relatively equal frequencies. Several explanations for the production of two forms of α chains in BALB/c mice are presented. The α chain of NB hemoglobin shows three amino acid replacements when compared with that of C57BL: NB has valine rather than glycine at position 26, isoleucine rather than valine at position 62, and serine rather than asparagine at position 68.