CDNA-DERIVED AMINO-ACID-SEQUENCE OF A LAND TURTLE (GEOCHELONE CARBONARIA) BETA-CHAIN HEMOGLOBIN

The cDNA sequence encoding the turtle Geochelone carbonaria beta-chain was determinated. The isolation of hemoglobin mRNA was based on degen erate primers' PCR in combination with 5'- and 3'-RACE protocol. The f ull 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 f ound at position 599. The deduced polypeptyde contains 146 amino-acid residues. The predicted amino acid sequence shares 83% identity with t he beta-globin of a related specie, the aquatic turtle C. p. belli. Ot herwise, identity is higher when compared with chicken beta-Hb (80%) t han with other reptilian orders (Squamata, 69%, and Crocodilia, 61%). Compared with human HbA, there is 67% identity, and at least three ami no acid substitutions could be of some functional significance (Glu43 beta-->Ser, His 116 beta--> Thr and His143 beta-->Leu). To our knowled ge this represents the first cDNA sequence of a reptile globin gene de scribed.