Primary Structure and Functional Properties of the Hemoglobin from the Free-Tailed BatTadarida brasiliensis(Chiroptera). Small Effect of Carbon Dioxide on Oxygen Affinity

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Abstract
The hemoglobin of the Free-Tailed Bat Tadarida brasiliensis (Microchiroptera) comprises two components (Hb I and Hb II) in nearly equal amounts. Both hemoglobins have identical .beta.-chains, whereas the .alpha.-chains differ in having glycine (Hb I) or aspartic acid (Hb II) in position 115 (GH 3). The components could be isolated by DEAE-Sephacel chromatography and separated into the globin chains by chromatography on carboxymethyl-cellulose CM-52. The sequences have been determined by Edman degradation with the film technique or the gas phase method (the .alpha.I-chains with the latter method only), using the native chains and tryptic peptides, as well as the C-terminal prolylpeptide obtained by acid hydrolysis of the Asp-Pro bond in the .beta.-chains. The comparison with human hemoglobin showed 18 substitutions in the .alpha.-chains and 24 in the .beta.-chains. In the .alpha.-chains one amino-acid exchange involves and .alpha.1/.beta.1-contact. In the .beta.-chains one heme contact, three .alpha.1/.beta.1- and one .alpha.1/.beta.2-contacts are substituted. A comparison with other chiropteran hemoglobin sequences shows similar distances to Micro- and Megachiroptera. The oxygenation characteristics of the composite hemolysate and the two components, measured in relation to pH, Cl-, and 2,3-bis-phosphoglycerate, are described. The effect of carbon dioxide on oxygen affinity is considerably smaller than that observed in human hemoglobin, which might be an adaptation to life under hypercapnic conditions.

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