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One might think that after over 100 years of study we now know all there is to know about Hemoglobin and its function. However, the purpose of this review is to outline that this fascinating protein has still much to say in the field of biological modulation. Hence, we like to focus on a number of parallel functions of hemoglobin besides its basic function of oxygen transport. Among these we like to recall the following main functions: a) modulation of erythrocyte metabolism; b) Heme oxidation and erythrocytes senescence; c) resistance to malaria; d) molecular heat transducer e) Enzymatic activity; f) Hemorphins, carbon monoxide and nitric oxide. [ABSTRACT FROM AUTHOR]

This article reports the role of resveratrol in the erythrocyte as a result of its interaction with hemoglobin and describes the effect of this interaction on the metabolism, the redox state, and the release of ATP. The drug crosses the erythrocyte membrane and binds to hemoglobin, altering its modulation and the release of ATP. Our study correlates the variation of the phosphorylation balance induced by resveratrol with the change in the intracellular concentration of ATP and with the decrease in ATP release from red blood cell and the consequent paracrine alteration on the vascular epithelium. Molecular docking calculations indicate larger specificity of binding for oxy-hemoglobin that correlates well with the stabilization of the R-quaternary structure and with the functional modulation of resveratrol on the protein. Finally, we locate a putative binding site at the central cavity of hemoglobin and characterize its key interacting residues with the drug. Computational results support the assumption that resveratrol may act as a protector agent against oxidative protein damage by interacting with hemoglobin. [ABSTRACT FROM AUTHOR]

Resveratrol, an important phytoalexine found in many plants, has been shown to be significantly effective in the treatment of several pathological conditions such as cancer, coronary heart disease and osteoarthritis. This study focuses on the effects of this drug on human red blood cells. In particular, we have examined the influence of resveratrol on Band 3, the anion exchanger protein, and hemoglobin as a function of the oxygenation-deoxygenation cycle. Moreover, special attention has been given to the metabolic changes imposed by caspase 3 activation. Resveratrol has proved to lower superoxide production, thereby decreasing heme-iron oxidation and saving the reducing power required for met-hemoglobin reduction. Oxygen binding experiments showed that resveratrol interacts with hemoglobin, shifting the T→R conformational transition towards the higher-affinity R state. This might contribute to altering the metabolic balance of the cell through an intensification of the pentose phosphate pathway. Moreover, at high oxygenation levels of the erythrocytic hemoglobin, resveratrol induces a significant activation of caspase 3, the action of which on Band 3 has a strong impact on cellular metabolism and anion transport. [ABSTRACT FROM AUTHOR]

O2carriers (extracellular and intracellular as well as monomeric and multimeric) have evolved over the last billion of years, displaying iron and copper reactive centers; very different O2carriers may co-exist in the same organism. Circulating O2carriers, faced to the external environment, are responsible for maintaining an adequate delivery of O2to tissues and organs almost independently of the environmental O2partial pressure. Then, intracellular globins facilitate O2transfer to mitochondria sustaining cellular respiration. Here, molecular aspects of multiple strategies evolved for O2transport and delivery are examined, from the simplest myoglobin to the most complex giant O2carriers and the red blood cell, mostly focusing on the aspects which have been mainly addressed by the so called 'Rome Group'. [ABSTRACT FROM AUTHOR]

The suborder Notothenioidei dominates the Antarctic ichthyofauna. The non-Antarctic monotypic family Pseudaphritidae is one of the most primitive families. The characterization of the oxygen-transport system of euryhaline Pseudaphritis urvillii is herewith reported. Similar to most Antarctic notothenioids, this temperate species has a single major hemoglobin (Hb 1, over 95% of the total). Hb 1 has strong Bohr and Root effects. It shows two very uncommon features in oxygen binding: At high pH values, the oxygen affinity is exceptionally high compared to other notothenioids, and subunit cooperativity is modulated by pH in an unusual way, namely the curve of the Hill coefficient is bell-shaped, with values approaching 1 at both extremes of pH. Molecular modeling, electronic absorption and resonance Raman spectra have been used to characterize the heme environment of Hb 1 in an attempt to explain these features, particularly in view of some potentially important nonconservative replacements found in the primary structure. Compared to human HbA, no major changes were found in the structure of the proximal cavity of the α-chain of Hb 1, although an altered distal histidyl and heme position was identified in the models of the β-chain, possibly facilitated by a more open heme pocket due to reduced steric constraints on the vinyl substituent groups. This conformation may lead to the hemichrome form identified by spectroscopy in the Met state, which likely fulfils a potentially important physiological role. [ABSTRACT FROM AUTHOR]

The Gymnothorax unicolor hemoglobin system is characterized by two components, called cathodic and anodic on the basis of their isoelectric point, which were separated by ion-exchange chromatography. The oxygen-binding properties of the purified components were studied in the absence and presence of chloride and/or GTP or ATP in the pH range 6.5–8.0. Stripped cathodic hemoglobin showed a small reverse Bohr effect, high oxygen affinity, and low co-operativity; the addition of chloride only caused a small decrease in oxygen affinity. In the presence of GTP or ATP, the oxygen affinity was dramatically reduced, the co-operativity increased, and the reverse Bohr effect abolished. Stripped anodic hemoglobin is characterized by both low oxygen affinity and co-operativity, and displayed a normal Bohr effect; the addition of chloride increased co-operativity, whereas ATP and GTP significantly modulated oxygen affinity at acidic pH values, enhancing the Bohr effect and giving rise to the Root effect. The complete amino-acid sequences of the α and β chains of both hemoglobins were established; the molecular basis of the functional properties of the hemoglobins is discussed in the light of the primary structure and compared with those of other fish hemoglobins. [ABSTRACT FROM AUTHOR]

A study was made of the haemoglobin (Hb) system from the Sardinian dwarf horse (Equus caballus jara), one of the last surviving wild horse species in Europe. The oxygen binding properties of the whole haemolysate and of the four different horse Hbs, separated by ion-exchange chromatography, were studied with special regard to the effect of chloride, 2,3-diphosphoglycerate and lactate. Results indicate that no significant functional differences exist between the four Hb components of horse haemolysate. Moreover, the molecular basis of the intrinsically low oxygen affinity and of the weak interaction of horse Hb with 2,3-diphosphoglycerate is discussed in the light of the primary structure of the molecule and of the results of a computer modelling approach. On these bases, it is suggested that the A1 (Thr→Ser) and A2 (Pro→Gly) substitutions observed in the β chains from horse Hb may be responsible for the displacement of the A helix that is known to be a key structural feature of those Hbs that display an altered interaction with 2,3-diphosphoglycerate as compared with human Hb. [ABSTRACT FROM AUTHOR]

Concerning the number and type of the hemoglobin components, the moray Muraena helena is characterized by three different phenotypes whose frequencies are nearly identical. Thus, the cathodal component is present in all individuals, whereas one or both of two amodal components may be present in the same phenotype. These components have been separated by chromatography. The oxygen binding properties of the purified hemoglobin components have been studied in the absence and presence of saturating concentrations of ATP or GTP and as a function of pH. The cathodal component shows an intrinsic O2 affinity four times higher than that of both anodal components, a very small Bohr effect and a significant decrease in O2 affinity upon addition of ATP and GTP (three and four times respectively with respect to stripped conditions), the latter being more effective than the former over the entire pH range examined. The anodal components do not appear functionally distinguishable and show the presence of an enhanced Bohr effect (Root effect) that is under the strict control of nucleotide triphosphates ATP, GTP, which, unlike in the cathodic component, exert the same effect on oxygen affinity. The complete sequence of the β chains of the cathodal and of one of the anodal components have been determined. The possible molecular basis of these different functional characteristics are discussed in the light of the globin sequence and of those amino acid residues which are known to be responsible of hemoglobin functional behaviour. [ABSTRACT FROM AUTHOR]

The oxygen binding of whole blood from humans and two arctic mammals, reindeer and muskox, has been studied as a function of carbon dioxide and temperature. All bloods display a marked Bohr effect with Bohr coefficients in the range −0.44-−0.73. The Bohr effect is more pronounced at 20°C. The temperature sensitivity of reindeer and muskox blood expressed by the apparent heat of oxygenation, δH, is almost three times lower than that of human HbA under the same experimental conditions. This thermodynamic difference gives special benefits to arctic mammals with large heterothermy by safeguarding oxygen unloading at very low ambient temperatures. [ABSTRACT FROM AUTHOR]

Abstract: Hemolysate from white stork displayed a single hemoglobin component, thus resulting into two bands and two globin peaks in dissociating PAGE and reversed phase-HPLC, respectively. Stripped hemoglobin showed an oxygen affinity higher than that of human HbA, a small Bohr effect, and a cooperative oxygen binding. A small decrease of oxygen affinity, of the same extent in all the pH range examined, was observed by addition of chloride, thus indicating an unusual chloride-independent Bohr effect (ΔlogP 50 /Δlog pH=−0.24). Saturating amounts of inositol hexakisphosphate, largely decreased hemoglobin-oxygen affinity (ΔlogP 50 =1.17 at pH 7.0), and increased the extent of its Bohr effect (ΔlogP 50 /ΔlogpH=−0.45). The phosphate binding curve allowed to measure a very high overall binding constant (K =1.18×105 M−1). The effect of temperature on the oxygen affinity was measured, and the enthalpy change of oxygenation resulted almost independent on pH. Structural–functional relationships are discussed by considering some amino acid residues situated at α1/β1 and α1/β2 interfaces, such as α38 and α89 positions. The presence of only one hemoglobin component, a rare event among birds, and its functional properties have been related to the physiological oxygen requirements of this soaring migrant bird and to its technique of flight during migration. [Copyright &y& Elsevier]

Amyloid β-peptide, the central constituent of senile plaques in Alzheimer’s disease brain, has been shown to be a source of free radical oxidative stress that may lead to neurodegeneration. In particular, it is well known that oxidation of methionine 35, is strongly related to the pathogenesis of Alzheimer’s disease, since it represents the residue in the β-amyloid peptide most susceptible to oxidation “in vivo”. In this study, the fragment 31–35 of the β-amyloid peptide, which has a single methionine at residue 35, was used to investigate the influence of the oxidation state of methionine-35 on the β-amyloid peptide (31–35) mediated cytotoxic effects. Because no extensive studies have yet addressed whether amyloid β peptides-mediated toxic effects can occur in the absence of mitochondria, human red blood cells were used as cell model. Exposure of intact red blood cells to β-amyloid peptide (31–35) induced a marked stimulation (∼45%) of the pentose phosphate pathway and a significant inhibition of the red cell enzyme catalase, compared with the results observed in control red blood cells. In contrast, exposure of red blood cells to the β-amyloid peptide (31–35)-Met35OX i.e. in which the sulfur of methionine is oxidised to sulfoxide, induced a slight activation of PPP (∼19%), and an inhibition of catalase activity lower with respect to the results observed in β-amyloid peptide (31–35)-treated red blood cells. Since the activities of red cell phosphofructokinase, glucose-6-phosphate dehydrogenase, glutathione peroxidase, glutathione reductase and the functionality of hemoglobin were not modified within the red cell following to β-amyloid peptides exposure, it is likely that β-amyloid (31–35)–catalase interaction may represent a selective toxic event. Together, these results support the hypothesis that Aβ peptide and the oxidative state of Met-35 may be involved in the mechanisms responsible of neurodegeneration in Alzheimer’s disease. [Copyright &y& Elsevier]

Sulfate transport by band-3 protein in adult human erythrocytes was shown to be modulated by oxygen pressure. In particular, a higher transport activity was measured under high oxygen pressure than at low one (0.0242±0.0073 vs. 0.0074±0.0010 min−1). Other factors, such as magnesium ions and orthovanadate, which can indirectly affect the binding properties of the cytoplasmic domain of band 3 (cdb3), influence significantly the anion exchanger activity. No effect of oxygen pressure on sulfate transport was found in chicken erythrocytes, which may be related to their lacking the cdb3 binding site. These findings are fully consistent with a molecular mechanism where the oxygen-linked transition of hemoglobin (T→R) could play a key role in the regulation of anion exchanger activity. [Copyright &y& Elsevier]