Studies on the functional properties of fish haemoglobins, I. The O2 equilibrium of trout haemoglobin

Giovenco, S.; Binotti, Ines; Brunori, Maurizio; Antonini, Eraldo

doi:10.1016/0020-711x(70)90007-8

Cited by 19 publications

(1 citation statement)

References 12 publications

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“…This was prepared from freshly drawn blood as described previously [ 1,2]. Separation of the various components has been carried out by column chromatography on DEAE-Sephadex A-50 ; their homogeneity was tested by starch-gel electrophoresis.…”

Section: Trout Hemoglobinmentioning

confidence: 99%

Studies on the Properties of Fish Hemoglobins Molecular Properties and Interaction with Third Components of the Isolated Hemoglobins from Trout (Salmo irideus)

Brunori

Giardina

Chiancone

et al. 1973

European Journal of Biochemistry

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This paper reports some physico-chemical and functional properties of two of the isolated hemoglobin components from trout (Salmo irideus) blood (Hb trout I and Hb trout IV).Both hemoglobins in the oxygenated state are tetrameric a t pH between 7 and 7.8 and protein concentration above x 0.1 mg/ml. The tetramer is extremely stable towards dissociation into subunits and the stability constants, estimated by differential gel filtration, are between 10 and 50 times larger than that of human hemoglobin in phosphate buffer. A very small degree of dissociation is also suggested by the very small extent of hybrid formation even in concentrated K I or triethanobmine.The dichroic properties of both Hb trout I and Hb trout IV show distinct features in the wavelength region between 300 and 200 nm. H b trout IV resembles human hemoglobin in the shape of the CO spectrum and in the values of the reduced ellipticity ( 6 ) ; furthermore upon deoxygenation the value of 8 a t 222 nm becomes more negative by about 5O/,. On the other hand H b trout I shows a different circular dichroism spectrum and in particular the ellipticity a t 222 nm is lower than that of H b trout IV. Moreover the spectrum is insensitive to the presence of heme ligands.Hb trout IV binds human haptoglobin (Hp) as shown by quenching of the fluorescence of the tryptophanyl residues of Hp upon addition of hemoglobin. The apparent stoichiometry of complex formation corresponds to two H b tetramers per H p molecule (while for human hemoglobin the stoichiometry corresponds to one tetramer per Hp). A clear cut effect of H p binding is observed on the kinetics of 0, and especially CO combination as studied by flash photolysis.The effect of several third components on the 0, equilibrium of both Hb trout I and IV has been investigated. I n general the effect of adding ions or other molecules to a solution of Hb trout I is very minor. On the other hand Hb trout IV is more susceptible to changes in solvent composition. Of particular importance is the action of ATP, the physiological organic phosphate, which is without effect on Hb trout I, while it has a clear effect on Hb trout IV. The addition of ATP shifts the Root effect, the characteristic property of Hb trout IV, to higher pH values, thereby acting as one of the allosteric effectors.It was shown in the previous papers of this series property of Hb trout IV, i.e. of that component which is present in the blood in larger amounts (%65O/, of the total). On the other hand the 0, binding properties of both Hb trout I and Hb trout I1 are invariant with pH, although the equilibrium curve is markedly cooperative (n = 2.5).The functional differences between the various components have been used to interprete the physiological role played by each of them in the economy of the organism [4]. It is clear that knowledge Eur. J. Biochem. 39 (1973)

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Section: Trout Hemoglobinmentioning

confidence: 99%

Studies on the Properties of Fish Hemoglobins Molecular Properties and Interaction with Third Components of the Isolated Hemoglobins from Trout (Salmo irideus)

Brunori

Giardina

Chiancone

et al. 1973

European Journal of Biochemistry

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Oxygen‐binding properties of hemoglobins from estivating and active African lungfish

et al. 1977

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The oxygen-binding characteristics and the multiplicity of the stripped hemoglobiin from active lungfish Protopterus amphibius, are the same as in specimens that have been estivating for about 30 months, showing that alteration in the hemoglobin molecules is not involved in the earlier reported increase in oxygen affinity of whole blood during estivation (Johansen et al., '76). At pH 7.0 and 26 degrees C the hemolysates show a high oxygen affinity (P50 = 3.1 Torr), a Bohr factor (delta log P50/delta pH) of - 0.33, and a cooperativity coefficient (n) of 1.7. Between 15 and 26 degrees C, the apparent heat of oxygenation (delta H) is - 8.6 Kcal-mole-1 at pH 7.0, corresponding with data for other fish. A low sensitivity of oxygen affinity to urea appears to be adaptive to the high urea concentrations in estivating lungfish. The salt sensitivity is, however, similar to human hemoglobin. The hemoglobin consists of two major (electrophoretically anodal) components, which differ slightly in oxygen affinity but are both sensitive to pH and nucleoside triphosphates (NTP). Guanosine triphosphate (GTP), the major erythrocytic organic phosphate, however, depresses the oxygen affinity of the composite and separated hemoglobins more effectively than ATP suggesting that GTP is the primary modulator of oxygen affinity. Comparative measurements reveal only one major hemoglobin component in P. annectens which has a markedly lower oxygen affinity and phosphate sensitivity than P. amphibius hemoglobins and thus seems less pliable to phosphate-mediated variation in oxygen affinity. The data are discussed in relation to the hemoglobin systems of other fish.

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On Allosteric Models

Wyman

1973

Dynamic Aspects of Conformation Changes in Biological Macromolecules

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Studies on the functional properties of fish haemoglobins, I. The O2 equilibrium of trout haemoglobin

Cited by 19 publications

References 12 publications

Studies on the Properties of Fish Hemoglobins Molecular Properties and Interaction with Third Components of the Isolated Hemoglobins from Trout (Salmo irideus)

Studies on the Properties of Fish Hemoglobins Molecular Properties and Interaction with Third Components of the Isolated Hemoglobins from Trout (Salmo irideus)

Oxygen‐binding properties of hemoglobins from estivating and active African lungfish

On Allosteric Models

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