Trout hemoglobin: Oxygen binding at sub‐zero temperatures

Giardina, Bruno; Brunori, Maurizio

doi:10.1016/0014-5793(76)80835-6

Cited by 7 publications

(2 citation statements)

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“…Expressed in terms of conformational changes, it may be stated that the latter effect is related to quaternary, and the former to tertiary pH-dependent structural transitions. Experimental data suggesting that both mechanisms may be present in fish haemoglobins were reported (Giardina et al, 1976;Giacometti et al, 1976).…”

Section: Vol 175mentioning

confidence: 86%

“…With trout Hb IV, 02 equilibrium experiments performed at sub-zero temperatures (Giardina et al, 1976) and at high oxygen pressures (Brunori et al, 1978) showed a heterogeneous binding curve at a pH where CO binding is not heterogeneous. Therefore, for this protein, binding data with two different ligands (02 and CO) show that tertiarylinked heterotropic effects are more marked for 02 than for CO. For aruana haemoglobin the functional heterogeneity for 02 is three times more pronounced than for CO, as can be seen from the data in Table 1.…”

Section: Discussionmentioning

confidence: 99%

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A comparative approach to protein-and ligand-dependence of the Root effect for fish haemoglobins

Giardina

Giacometti

Coletta

et al. 1978

Biochemical Journal

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Ligand-binding equilibria, kinetics and (13)C n.m.r. spectra of bound (13)CO, of the haemoglobins from two fishes that are very distant on the evolutionary scale, i.e. the fourth haemoglobin component from Salmo irideus and the single component from Osteoglossum bicirrhosum, were studied. The C-terminal sequence was also determined for the haemoglobin from Osteoglossum. The results show that (i) the C-terminal residues of both chains are not directly responsible for the characteristic heterotropic effect known as Root effect, since for both fish haemoglobins these residues are identical with those of human haemoglobins. (ii) In all haemoglobins characterized by the Root effect a dependence of the (13)CO n.m.r. resonances on pH is observed. However, the extent of the shift(s) depends on the particular protein, and is probably the result of a combination of both tertiary and quaternary conformational changes. (iii) Both haemoglobins from trout and Osteoglossum manifest a functional heterogeneity between the two types of chains in the tetramer, which increases with proton activity. For CO, the effect is very small for trout haemoglobin IV, and very marked for Osteoglossum haemoglobin; for O(2) strongly heterogeneous binding curves were obtained at approx. pH6.2 with both haemoglobins. (iv) Estimations of the relative values of the affinity constants for the alpha and beta chains in the tetramer were obtained for both haemoglobins from (13)CO n.m.r. spectra at low fractional saturation. On the basis of these findings the molecular mechanism underlying the Root effect is discussed.

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Section: Vol 175mentioning

confidence: 86%

Section: Discussionmentioning

confidence: 99%