Chloride binding and the Bohr effect of human fetal erythrocytes and HbFII solutions

Poyart, Claire; Bursaux, E; Guesnon, P; Teisseire, B

doi:10.1007/bf00581580

Cited by 8 publications

(5 citation statements)

References 36 publications

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“…We tested a 10-fold excess of 2,3-DPG to Hb to ensure that the maximum effect of the allosteric regulator would be achieved. A significant lowering of the oxygen affinity of HbA was found, but a smaller effect on HbF was noted, consistent with previous reports (1,27). The effect of 2,3-DPG on HbA/F at 2.5-, 5.0-, and 10.0-fold (data shown) DPG/Hb ratios was virtually the same as that for HbF and unlike that for HbA, even though the amino acids in its DPG binding site are the same as those in HbA.…”

Section: Effect Of Protons On Hba and Hbf Tetramersupporting

confidence: 92%

Exchange of Subunit Interfaces between Recombinant Adult and Fetal Hemoglobins

Dumoulin

Manning

Jenkins

et al. 1997

Journal of Biological Chemistry

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The inter-relationship between the interior subunit interfaces and the exterior diphosphoglycerate (DPG) binding region of the hemoglobin tetramer and the effects of a specific N-terminal acetylation on tetramer assembly have been evaluated. Tetrameric fetal hemoglobin F in the liganded state was found to dissociate to dimers much less than previously appreciated, i.e. about 70 times less than adult hemoglobin A (K d ‫؍‬ 0.01 M and 0.68 M, for HbF and HbA, at pH 7.5, respectively) over the pH range 6.2-7.5, whereas HbF 1 , in which the N termini of the ␥-chains are acetylated, dissociates like HbA. To determine whether this feature of HbF could be transferred to hemoglobin A, the single amino acid difference in their ␣ 1 ␤ 2 /␣ 1 ␥ 2 interfaces and the 4 amino acid differences in their ␣ 1 ␤ 1 /␣ 1 ␥ 1 interfaces have been substituted in HbA to those in HbF. This pentasubstituted recombinant HbA/F had the correct molecular weight as determined by mass spectrometry, the expected mobility on isoelectric focusing, the calculated amino acid composition, and normal circular dichroism properties, oxygen binding, and cooperativity. Although HbA/F has the same amino acid side chains that bind DPG as HbA, its diminished response to 2,3-DPG resembled that of HbF. However, its tetramer-dimer dissociation constant (K d ‫؍‬ 0.14 M) was between that of HbA and HbF despite the fact that it was composed entirely of HbF subunit interfaces. The results indicate that regions of the tetramer distant from the tetramer-dimer interface influence its dissociation and, reciprocally, that the interfaces affect regions involved in the binding of allosteric regulators, suggesting flexible long range inter-relationships in hemoglobin.

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Section: Effect Of Protons On Hba and Hbf Tetramersupporting

confidence: 92%

Exchange of Subunit Interfaces between Recombinant Adult and Fetal Hemoglobins

Dumoulin

Manning

Jenkins

et al. 1997

Journal of Biological Chemistry

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“…Hence, HbF has more buffering capacity because of its enhanced ability to absorb protons. This difference may contribute to the different functional responses of each type of hemoglobin tetramer, e.g., their alkaline Bohr effects, which has long been considered to be essential for the transfer of O 2 from maternal HbA to fetal HbF ( , ); i.e., more of the protons released upon oxygenation of T state tetramers of HbA would be reabsorbed by the αβ dimers than would occur with the lower concentrations of αγ dimers from HbF. Therefore, the net proton release during oxygenation of tetramers would be greater for HbF than for HbA.…”

Section: Resultsmentioning

confidence: 99%

“…(2) Just as the Bohr effect, which is considered to have a physiological role in the O 2 transfer between HbA and HbF (1,2,18), is due to the reversible protonation of a small number of specific sites in the T and R state tetramers [the N-terminus of the R-subunits and the C-terminus of the βor γ-subunits (18)], the specific protonation of a different site, Gly-1(γ), confers a selective tetramer strength to HbF. In this instance, however, it is the tightening of an interface in the R state that is involved rather than its rearrangement, which occurs in the alkaline Bohr effect involving R and T states.…”

Section: Resultsmentioning

confidence: 99%

“…Differences in the functional properties of HbF and HbA, such as O 2 binding and its pH dependence (alkaline Bohr effect) as well as the effects of allosteric regulatory molecules in the physiological pH range, control the important process involving the transfer of O 2 from the maternal to the fetal circulation ( , ). The control of other important events such as pH fluctuations and CO 2 removal is not as well understood although the general buffering effect of hemoglobin as well as the identity of specific sites that react with CO 2 are known ( , ).…”

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confidence: 99%

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The Acetylation State of Human Fetal Hemoglobin Modulates the Strength of Its Subunit Interactions: Long-Range Effects and Implications for Histone Interactions in the Nucleosome

Manning

2001

Biochemistry

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The source of the 70-fold increased tetramer strength of liganded fetal hemoglobin relative to that of adult hemoglobin between pH 6.0 and 7.5 reported earlier [Dumoulin et al. (1997) J. Biol. Chem. 272, 31326] has been identified as the N-terminal Gly residue of the gamma-chain, which is replaced by Val in adult hemoglobin. This was revealed by extending the study of the pH dependence of the tetramer-dimer equilibrium of these hemoglobins into the alkaline range as far as pH 9. From pH 7.5 to 9.0, the 70-fold difference in the association equilibrium constant between hemoglobins F and A lessened progressively. This behavior was attributed to the difference in the pK(a) 8.1 of Gly-1(gamma) compared to the pK(a) 7.1 value of Val-1(beta) of hemoglobins F and A, respectively. Evidence for this conclusion was obtained by demonstrating that natural hemoglobin F(1), which is specifically acetylated at Gly-1(gamma) and hence unable to be protonated, behaves like HbA and not HbF in its tetramer-dimer association properties over the pH range studied. An increased degree of protonation of the gamma-chain N-terminus of hemoglobin F from pH 9.0 to 8.0 is therefore suggested as responsible for its increased tetramer strength representing an example of transmission of a signal from its positively charged N-terminal tail to the distant subunit allosteric interface where the equilibrium constant is measured. An analogy is made between the effects of acetylation of the fetal hemoglobin tetramer on the strength of its subunit interactions and acetylation of some internal Lys residues within the N-terminal segments of the histone octamer around which DNA is wrapped in the nucleosome.

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“…In comparison with adult red cells the monooxygenase-like activity of the cytochrome P450 system appears to be 3-5 times higher (Blisard & Mieyal, 1980), and a higher activity of glucose-6-phosphate dehydrogenase and a lower activity of phosphofructokinase have been reported for fetal red cells (Gahr, Meves & Schroter, 1979). Poyart, Bursaux, Guesnon & Teisseire (1978) studied the chloride binding and Bohr effect in fetal cells and haemoglobin solutions and concluded that fetal haemoglobin has a lower affinity for chloride ions so that the acid Bohr effect is less, and hence the alkaline Bohr effect is increased compared to adult red cells.…”

Section: Discussionmentioning

confidence: 99%

Chloride and bicarbonate transport in fetal red cells.

Brahm

Wimberley

1989

The Journal of Physiology

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SUMMARY1. Chloride (Jc1) and bicarbonate (JHCO 3) self-exchange flux in fetal human red cells was studied at 0-38°C as 36CI-and [14C]HC03-efflux.2. Both at 0 and 38°C Jcl showed a bell-shaped pH dependence with a broad maximum at pH 7-8. Jcl was 997 % inhibited by the binding of 1. x 106 4,4'-diisothiocyanostilbene-2,2'-disulphonate (DIDS) molecules per cell membrane.3. By raising the temperature from 0 to 38°C Jcl, at external concentration (CO) = 150 mm, increased about 200 times to 5 x 10-8 mol/(cm2 s), the half-time of the tracer efflux being 80 ms at 38°C and pH 7-2. Under conditions where CO = (110 mMCl-+ 25 mM-HCO3-), Jcl also increased by about 200 times, while JHCO3 increased only about 100 times, as temperature was raised from 0 to 38 'C.4. The apparent activation energy (EA) of Janion was not constant, but increased gradually with decreasing temperature. Assuming that the change of EA with temperature consists of two components Jcl, under both experimental conditions, had average values of EA = 117-120 under and EA = 73-78 kJ/mol above a 'breaking' point at 15-20°C, while JHCO3 showed an EA = 100 below and EA = 48 kJ/mol above 25 'C.5. We conclude that the anion transport protein becomes built into the membrane at a very early stage of life, and that the kinetics of Janio in fetal red cells show characteristics that are similar to those of adult red cells.6. Our results suggest that the CO2 transport capacity of the fetal blood can be exploited during rest nearly as efficiently as that of adult blood.

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Chloride binding and the Bohr effect of human fetal erythrocytes and HbFII solutions

Cited by 8 publications

References 36 publications

Exchange of Subunit Interfaces between Recombinant Adult and Fetal Hemoglobins

Exchange of Subunit Interfaces between Recombinant Adult and Fetal Hemoglobins

The Acetylation State of Human Fetal Hemoglobin Modulates the Strength of Its Subunit Interactions: Long-Range Effects and Implications for Histone Interactions in the Nucleosome

Chloride and bicarbonate transport in fetal red cells.

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