Primary Structure of the Hemoglobins from Sphenodon(Sphenodon punctatus,Tuatara, Rynchocephalia). Evidence for the Expression of αD-Gene

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Abstract
Sphenodon is the sole representative of the "beakhead" reptiles which were widely distributed during the Triassic period before the spectacular rise of dinosaurs. Sphenodon punctatus is the only survivor ("living fossil") of this period. The morphological features of Sphenodon are remarkably conservative and differ little from reptiles living 200 million years ago. In the present paper the determination of the primary structure of the tetrameric hemoglobins is described: three components are identified: hemoglobin A'' (.alpha.2A .beta.2II), hemoglobin A (.alpha.2A .beta.2I) and hemoglobin D (.alpha.2D .beta.2II). The components were characterized electrophoretically, the four different peptide chains were characterized by Triton electrophoresis as well as by high-performance liquid chromatography. The hemoglobins and.sbd.under dissociating conditions.sbd.also the chains, were isolated on columns of cellulose ion exchangers. Sequence determination was carried out after cleavage of the individual chains with trypsin and after a specific chemical cleavage of the Asp-Pro bond. For sequence determination the film technique and gas-phase method were employed. The data are compared with the sequence of the human hemoglobin, and interpretations of the amino-acid sequences are given. Particularly notable is the evidence of hemoglobin D: this hemoglobin (.alpha.2D .beta.2II) is found only in birds, and in two cases in turtles. However, this component is not found in other retiles. The results make possible an interpretation of the relatively high oxygen affinity adn explain the lack of cooperativity (myoglobin properties) of these tetrameric hemoglobins.

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