Heterogeneity and polymerization of hemoglobins of Caiman latirostris (Crocodylia: Reptilia)

Reischl, Evaldo; Diefenbach, Carlos O. da C.

doi:10.1016/0305-0491(76)90137-1

Cited by 8 publications

(3 citation statements)

References 9 publications

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“…Hb polymerization commonly involves Cys residues, as evident from the correlation between disulfide bridge formation and polymerization in ectotherm Hbs (13,25,67,69,85). In human Hb mutants Mississippi (␤9Ser¡Cys) and Hb Ta-li (␤83Gly¡Cys), polymerization is induced by the incorporation of a single Cys residue (6).…”

Section: Polymerization and Its Effect On Hb-o 2 Bindingmentioning

confidence: 98%

“…Finding a unique combination of amino acid exchanges at highly conserved effector binding sites, we investigated the O 2 binding properties of the Hb and its sensitivities to chloride ions, ATP, DPG, and IHP, and to CO 2 and temperature, over a wide pH range to discern possible alternative allosteric regulatory mechanisms. On the basis of the aggregation of deoxygenated Hbs to octamers and larger polymers (that may occur in vivo) observed in a diverse array of sauropsid taxa (birds and nonavian reptiles) (67,71,80), we also assessed polymerization in dwarf caiman Hb, its dependence on oxygenation state, and its possible effects on Hb-O 2 affinity.…”

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confidence: 99%

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Lack of conventional oxygen-linked proton and anion binding sites does not impair allosteric regulation of oxygen binding in dwarf caiman hemoglobin

Weber

Fago

Malte

et al. 2013

American Journal of Physiology-Regulatory, Integrative and Comp

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In contrast to other vertebrate hemoglobins (Hbs) whose high intrinsic O2 affinities are reduced by red cell allosteric effectors (mainly protons, CO2, organic phosphates, and chloride ions), crocodilian Hbs exhibit low sensitivity to organic phosphates and high sensitivity to bicarbonate (HCO3(-)), which is believed to augment Hb-O2 unloading during diving and postprandial alkaline tides when blood HCO3(-) levels and metabolic rates increase. Examination of α- and β-globin amino acid sequences of dwarf caiman (Paleosuchus palpebrosus) revealed a unique combination of substitutions at key effector binding sites compared with other vertebrate and crocodilian Hbs: β82Lys→Gln, β143His→Val, and β146His→Tyr. These substitutions delete positive charges and, along with other distinctive changes in residue charge and polarity, may be expected to disrupt allosteric regulation of Hb-O2 affinity. Strikingly, however, P. palpebrosus Hb shows a strong Bohr effect, and marked deoxygenation-linked binding of organic phosphates (ATP and DPG) and CO2 as carbamate (contrasting with HCO3(-) binding in other crocodilians). Unlike other Hbs, it polymerizes to large complexes in the oxygenated state. The highly unusual properties of P. palpebrosus Hb align with a high content of His residues (potential sites for oxygenation-linked proton binding) and distinctive surface Cys residues that may form intermolecular disulfide bridges upon polymerization. On the basis of its singular properties, P. palpebrosus Hb provides a unique opportunity for studies on structure-function coupling and the evolution of compensatory mechanisms for maintaining tissue O2 delivery in Hbs that lack conventional effector-binding residues.

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Section: Polymerization and Its Effect On Hb-o 2 Bindingmentioning

confidence: 98%

mentioning

confidence: 99%

Lack of conventional oxygen-linked proton and anion binding sites does not impair allosteric regulation of oxygen binding in dwarf caiman hemoglobin

Weber

Fago

Malte

et al. 2013

American Journal of Physiology-Regulatory, Integrative and Comp

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“…Haemoglobin is the major protein in the red cell. The concentration of haemoglobin in the red cell is similar in all vertebrates and falls between 25 and 52 percent of net weight (Wintrobe, '1945 (Sullivan and Riggs, 1967) and diffuseness (Sullivan and Riggs, 1967;Reischl and Diefenbach, 1976). As Sullivan (1974) pointed out in his excellent review of reptilian haemoglobins, this "polymerization may simply reflect, after haemolysis, the absence of the reducing environment in the red cell and must be controlled if meaningful results are to be obtained".…”

Section: Physiology Of Red Cellsmentioning

confidence: 99%

Methemoglobin reduction in crocodile blood: Are high levels of MetHb typical of healthy reptiles?

Gruca

Grigg

1980

J. Exp. Zool.

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In 82 wild-caught Crocodylus porosus, levels of NADH-MetHb reductase and GSH seem adequate to maintain hemoglobin in its reduced functional state. Studies of C. porosus erythrocytes in vitro show reduction of metHb in the presence of lactate, glucose and plasma, but not pyruvate. These findings, together with recent data which show low metHb in a variety of reptiles, cast doubt on the accepted view that high levels of MetHb are typical of healthy reptiles. One explanation for the sharp contrast between earlier and more recent data could be technical. We found low metHb in Crocodylus johnstoni, Chelodina longicollis and Sphenomorphus quoyi. However, high and variable vales reminiscent of many of the earlier data were obtained by omitting final centrifugation prior to spectrophotometry. Interestingly, this step is not part of the standard clinical method but is necessary in analyses of blood with nucleated red cells. These observations suggest that high metHb may not be typical of reptiles after all.

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Vertebrate Hemoglobins

Ingermann¹

1997

Comprehensive Physiology

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Heterogeneity and polymerization of hemoglobins of Caiman latirostris (Crocodylia: Reptilia)

Cited by 8 publications

References 9 publications

Lack of conventional oxygen-linked proton and anion binding sites does not impair allosteric regulation of oxygen binding in dwarf caiman hemoglobin

Lack of conventional oxygen-linked proton and anion binding sites does not impair allosteric regulation of oxygen binding in dwarf caiman hemoglobin

Methemoglobin reduction in crocodile blood: Are high levels of MetHb typical of healthy reptiles?

Vertebrate Hemoglobins

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