Comparative analysis of the cDNA sequences derived from the larval and the adult alpha 1-globin mRNAs of Xenopus laevis.

The complete nucleotide sequences of cloned cDNA segments derived from the larval and the adult alpha 1-globin mRNA of Xenopus laevis have been determined. These sequences comprise part of the 5' noncoding region, the entire coding region and the 3' noncoding region, including the polyadenylation site. The larval sequence differs from the adult one by a much longer 3' noncoding region. The sequences diverge by 47%, but codon usage is similar. Comparison of the amino acid sequences of vertebrates shows that the sites of heme contact are highly conserved, whereas the alpha 1/beta 1- and the alpha 1/beta 11-interfaces diverge to different degrees. In these regions the larval alpha 1-globin diverges less from embryonic than from adult alpha-like globins of vertebrates. This suggests that these sites are mainly responsible for the functional peculiarities of the larval amphibian hemoglobins.