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  • Title: Hemoglobins of reptiles. The primary structure of the major and minor hemoglobin component of adult Western Painted Turtle (Chrysemys picta bellii).
    Author: Rücknagel KP, Braunitzer G.
    Journal: Biol Chem Hoppe Seyler; 1988 Feb; 369(2):123-31. PubMed ID: 3365328.
    Abstract:
    Red blood cells of adult Western Painted Turtles (Chrysemys picta bellii) contain two hemoglobin components: HbA (alpha A2 beta 2) and HbD (alpha D2 beta 2). We present the complete amino-acid sequences of the alpha A-chains from the major component and of the beta-chains common to both components. Structural features are discussed with respect to the animals extreme tolerance of severe hypoxic conditions during hibernation which is accompanied by a high oxygen affinity of the hemoglobin. The strong ATP dependence of Western Painted Turtle hemoglobin oxygen affinity is contrasted by the loss of one ATP-binding site, beta 143(H21)-Arg----Leu. The primary structure of the beta-chains excludes an allosteric control mechanism by hydrogencarbonate as it was found in crocodiles. Except in turtles a hemoglobin pattern with HbA and HbD sharing the same beta-subunits has been found only in birds. In comparison to other vertebrate hemoglobins there is a surprising similarity of the sequences to those of bird hemoglobins. alpha A- as well as alpha D-chains show larger homologies to chains of the same type in different species than alpha A- and alpha D-chains to each other in the same species. This indicates a duplication of the alpha-gene preceding the divergence of turtles and birds.
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