The Concentration Dependence of the Oxygen Affinity of Haemoglobin S

May, Anna; Huehns, E. R.

doi:10.1111/j.1365-2141.1975.tb00548.x

Cited by 63 publications

(18 citation statements)

References 47 publications

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“…The interior of an erythrocyte is essentially a highly concentrated solution of hemoglobin. The affinity of erythrocytes containing sickle cell hemoglobin (HbS) for oxygen depends significantly upon the intracellular hemoglobin concentration, because oxygen binding is linked to the polymerization of HbS (May and Huehns, 1975). The concentration dependence of oxygen affinity may be quantitatively accounted for if, and only if, steric repulsion between hemoglobin molecules is taken into account (Minton, 1976).…”

Section: Journal Of Cell Sciencementioning

confidence: 99%

How can biochemical reactions within cells differ from those in test tubes?

Minton

2006

Journal of Cell Science

381

246

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Nonspecific interactions between individual macro-molecules and their immediate surroundings (`background interactions') within a medium as heterogeneous and highly volume occupied as the interior of a living cell can greatly influence the equilibria and rates of reactions in which they participate. Background interactions may be either repulsive, leading to preferential size-and-shape-dependent exclusion from highly volume-occupied elements of volume, or attractive, leading to nonspecific associations or adsorption. Nonspecific interactions with different constituents of the cellular interior lead to three classes of phenomena: macromolecular crowding, confinement and adsorption. Theory and experiment have established that predominantly repulsive background interactions tend to enhance the rate and extent of macromolecular associations in solution, whereas predominately attractive background interactions tend to enhance the tendency of macromolecules to associate on adsorbing surfaces. Greater than order-of-magnitude increases in association rate and equilibrium constants attributable to background interactions have been observed in simulated and actual intracellular environments.

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Section: Journal Of Cell Sciencementioning

confidence: 99%

How can biochemical reactions within cells differ from those in test tubes?

Minton

2006

Journal of Cell Science

381

246

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“…This is more than would be required for the two p-Val(6) sites exposed per tetramer, and probably results from the inefficient nature of a non-covalent equilibrium type of binding. The increased oxygen affinity of HbS in the presence of Lys-Phe can be explained by the inhibition of polymerisation [24], since no effect was seen when normal HbA-containing cells were used. The effect on oxygen affinity was only seen after prolonged incubation which presumably reflects the time needed for Lys-Phe to enter the red cell.…”

Section: Discussionmentioning

confidence: 99%

A potent new dipeptide inhibitor of cell sickling and haemoglobin S gelation

Franklin¹,

Cotter²,

Cheetham³

et al. 1983

European Journal of Biochemistry

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A dipeptide L-lysine-L-phenylalanine is shown to inhibit both cell sickling and the gelation of solutions of sicklecell haemoglobin. The effect on deoxyhaemoglobin solutions and gels was followed by centrifugation ; a progressive inhibition of gelation was observed up to 30 mM Lys-Phe. The haemoglobin concentration at the plateau (26 g/dl) suggests that an effect might be seen in vivo if suitable concentrations of Lys-Phe (about 20 mM) can be maintained in the blood stream. Additional studies of lag time before onset of gelation support this. Oxygen dissociation curves of sickle cells showed an effect of Lys-Phe only after incubation for 3 h before measurement, the P,, decreasing from 51 mmHg (6.8 MPa) to 41 mmHg (5.5 MPa) for cells depleted of 2,3-bisphosphoglycerate.The effect of Lys-Phe on intact sickle cells was more rapid. A marked increase in the number of unsickled cells in the presence of Lys-Phe was observed after only 15 min incubation. This result, together with measurements of uptake both into the cell and onto the cell membrane shows that the compound produces a membrane-mediated antisickling effect in addition to the effect on haemoglobin in solution within the cell. The membrane effect is not due to a change in cell volume.The properties of this dipeptide may be of value in the treatment of impending and early sickle crisis.The changes in shape and flexibility of the sickle erythrocyte on deoxygenation are due to the aggregation of sickle cell haemoglobin to form extended fibrillar structures [l, 21. X-ray crystallographic studies of deoxygenated HbS [3] and X-ray diffraction of fibres [4] have revealed the sites of interaction with HbS molecules within the fibrils. These include the abnormal region of the P-chain containing valine A3(6), in one subunit, which interacts with the region 8-Phe(85)-P-Leu(SS), in a neighbouring subunit, and is the molecular basis of the hydrophobic deoxy-HbS polymerisation. Attempts to design a non-covalent and non-toxic anti-sickling agent have included examination of oligopeptides which mimic the primary sequence around these sites [S] and which might be expected to inhibit competitively the specific contacts involved in HbS polymerisation. The results obtained with these peptides were disappointing, and probably reflected an inefficient binding of competitor weakened by increased conformational entropy arising from its small size. Amino acids have also been tested for inhibitory activity [6,7] ; phenylalanine being the most effective. Amphipathic derivatives of phenylalanine [8] were more effective inhibitors of the polymerisation of deoxy-HbS, and this inhibition has been correlated with the effects of varying charge and hydrophobicity in phenylalaninerelated compounds [9 -11 1. A series of small molecules were designed to maximise hydrophobicity and red cell membrane permeabilility and these included the benzyl esters of aromatic amino acids 112). These were found to be potent inhibitors of whole cell sickling. No major effects on the properties of deoxy-HbS s...

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“…However, fresh erythrocytes in plasma failed to take up enough PLP for detection of PLP-Hb adducts (4). When normal erythrocytes were preincubated for 12 h at 370C, washed, and suspended in isotonic phosphate buffer, incubation with PLP for several hours produced substantial modification of Hb (5). Unfortunately, this process seems too complex for clinical use.…”

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confidence: 99%