Oxygen-binding properties of total hemoglobin and isolated components of the terrestrial tortoise Geochelone carbonaria

Torsoni, MA; Viana, R. I.; Stoppa, Graziela R.; Cesquini, Maristela; Barros, B. F.; Ogo, Satie Hatsushika

doi:10.1016/s0300-9629(96)00478-1

Cited by 4 publications

(8 citation statements)

References 30 publications

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“…An identical pattern was obtained for aged Hb solutions on PAGE. This finding contrasts with that for G. carbonaria in which the fresh Hb presented a complex electrophoretical pattern and varied with the duration of storage, demonstrating its polymerization capacity (Torsoni et al, 1997). The polymerization may be formed by disulfide bridges among tetramers.…”

Section: Discussioncontrasting

confidence: 75%

“…3). Thus, the two main Hb components possess the G1 globin chain, with the second globin chain dissimilar, showing a structural difference between them, as it also occurs in G. carbonaria (Torsoni et al, 1997). A similar situation has been observed in the turtles C. picta belli and P. hillarii, (Rucknagel et al, 1984) in which the two Hb components possess the same β chain.…”

Section: Discussionmentioning

confidence: 58%

“…The complexity of chelonian Hbs compared to that of mammalians is well demonstrated by the variety Hb components observed in hemolysates from several turtle species (Sullivan & Riggs, 1967a;Rucknagel et al, 1984;Torsoni et al, 1997). The chromatographic profile (Fig.…”

Section: Discussionmentioning

confidence: 97%

“…Gel filtration studies indicated that G. denticulata Hb did not polymerize, although polymerization is frequently seen in turtle Hbs (Sullivan & Riggs, 1967a;Reischl, 1989), including that of G. carbonaria (Torsoni et al, 1997), which is able to form aggregates larger than tetramers. Polymerization of turtle Hb may occur in vivo under conditions of environmental stress and in vitro, after hemolysis (Riggs et al, 1964;.…”

Section: Discussionmentioning

confidence: 99%

“…In general, the functional properties of hemoglobins (Hbs) appear to be well adapted to meet the different metabolic needs of animals and their environmental constraints. To examine the structure and function of Hb from closely related species of turtle, G. denticulata Hb was studied and compared with that of G. carbonaria Hb (Torsoni et al, 1997). These two species of turtle belong to the Testudinidae family.…”

Section: Introductionmentioning

confidence: 99%

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Functional behavior of tortoise hemoglobin Geochelone denticulata

et al. 2002

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The hemolysate from Geochelone denticulata contains two main hemoglobin components, as shown by ion exchange chromatography and polyacrylamide gel electrophoresis (PAGE). Electrophoresis under dissociating conditions showed three types of globin chains. The apparent molecular mass, as determined by gel filtration on Sephadex G-200, was compatible with tetrameric Hb, which was unable to polymerize. The G. denticulata Hb has a P50 value of 9.56 mm Hg at pH 7.4. The Hb oxygenation appears to be under the control of organic phosphates and hydrogen ion since it is strongly affected by those species. In the presence ATP or IHP the P50 values increased to 29.51 mm Hg and 54.95 mm Hg, respectively, at pH 7.4. The n50 was generally lower than 1.5 in stripped Hb, suggesting a dissociation of tetramers. In the presence of organic phosphates n50 values increased to approximately 2.5. The Bohr effect was evident in oxygen equilibrium experiments. The hematocrit (32%) and Hb concentration (5.7 mM as heme) of G. denticulata blood were substantially larger than those of G. carbonaria, but the methemoglobin levels were similar in both species, approximately 1%. Thus, the oxygen capacity of blood appears to be higher in G. denticulata than in G. carbonaria, particularly considering the functional properties of their Hbs, which would guarantee the survival of animals.

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Section: Discussioncontrasting

confidence: 75%

Section: Discussionmentioning

confidence: 58%

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Functional behavior of tortoise hemoglobin Geochelone denticulata

et al. 2002

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Low Oxygen Affinity in Reptilian Hemoglobin D: Prediction of Residue Interactions in Geochelone carbonaria HbD by Homology Modeling

et al. 2007

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The homology model of hemoglobin D from Geochelone carbonaria, the red-footed tortoise was predicted using the 3D structure coordinates of Geochelone gigantea hemoglobin D as the template. The model was built using the program, MODELLER (8v1) and evaluated with PROCHECK and PROSA. The present study features an in-depth analysis of the 3D model and its conformational changes brought about with variations in its environment. These structural changes are correlated with its ability to adapt to different environmental constraints enabling the organism to better suit to its natural habitat. The model shows additional contacts between amino acid pairs of alpha-119 and beta-55, alpha-35 and beta-124, alpha-103 and beta-112, alpha-115 and beta-116, alpha-120 and beta-52, alpha-120 and beta-55, alpha-36 and beta-127 which are not found in human hemoglobin. It is predicted that these contacts may result in T-state stabilization thus lowering oxygen affinity. Furthermore, decrease in the interaction of phosphate heteroatoms with the amino acid residues of G. carbonaria Hb was also predicted in this study.

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