cDNA-derived amino-acid sequence of a land turtle (Geochelone carbonaria) β-chain hemoglobin

Abstract

The cDNA sequence encoding the turtle Geochelone carbonaria β-chain was determinated. The isolation of hemoglobin mRNA was based on degenerate primers' PCR in combination with 5'- and 3'-RACE protocol. The full length cDNA is 615 bp with the ATG start codon at position 53 and TGA stop codon at position 495; The AATAAA polyadenylation signal is found at position 599. The deduced polypeptyde contains 146 amino-acid residues. The predicted amino acid sequence shares 83% identity with the β-globin of a related specie, the aquatic turtle C. p. belli. Otherwise, identity is higher when compared with chicken β-Hb (80%) than with other reptilian orders (Squamata, 69%, and Crocodilia, 61%). Compared with human HbA, there is 67% identity, and at least three amino acid substitutions could be of some functional significance (Glu43β→Ser, His116β→Thr and His143β→Leu). To our knowledge this represents the first cDNA sequence of a reptile globin gene described.