The amino acid sequences of two α chains of hemoglobins from Komodo dragon Varanus komodoensis and phylogenetic relationships of amniotes

Abstract

To elucidate phylogenetic relationships among amniotes and the evolution of α globins, hemoglobins were analyzed from the Komodo dragon (Komodo monitor lizard) Varanus komodoensis, the world's largest extant lizard, inhabiting Komodo Islands, Indonesia. Four unique globin chains (α(A), α(D), β(B), and β(C)) were isolated in an equal molar ratio by high performance liquid chromatography from the hemolysate. The amino acid sequences of two α chains were determined. The α(D) chain has a glutamine at E7 as does an α chain of a snake, Liophis miliaris, but the α(A) chain has a histidine at E7 like the majority of hemoglobins. Phylogenetic analyses of 19 globins including two α chains of Komodo dragon and ones from representative amniotes showed the following results: (1) The a chains of squamates (snakes and lizards), which have a glutamine at E7, are clustered with the embryonic α globin family, which typically includes the α(D) chain from birds; (2) birds form a sister group with other reptiles but not with mammals; (3) the genes for embryonic and adult types of α globins were possibly produced by duplication of the ancestral α gene before ancestral amniotes diverged, indicating that each of the present amniotes might carry descendants of the two types of α globin genes; (4) squamates first split off from the ancestor of other reptiles and birds.