The complete primary structure of the marine carnivora,galapagoes fur seal (Arctocephalus galapagoensis,Otariidae) hemoglobins

The complete primary structure of the two hemoglobin components of the fur seal (Arctocephalus galapagoensis) is presented. The two components (HbI and HbII) occur in nearly equal amounts and have identical β-chains; whereas the two α-chains (αI/αII) differ by six exchanges Ile/Val, Met/Thr, Ser/Ala, Pro/His, Lys/Gly, and Thr/Ala at positions 10, 34, 35, 50, 78, and 131, respectively. The components were isolated by DEAE-Sephacel chromatography and were separated into the globin chains by RP-HPLC on a column of Nucleocil-C4. The sequences have been determined by Edman degradation in liquid- and gas-phase sequencer, using the native chains and tryptic peptides. The sequences compared with those of other Carnivora species and an adult human globin chains. An identical β-chain is found in fur seal and walrus, whereas larger differences were found between αI and αII compared to β-chains.     

The tryptic peptides of coyote (Canis latrans) hemoglobin

The tryptic peptides from α- and β-chains of coyote (Canis latrans) hemoglobin have been isolated and their amino acid compositions determined. The compositions are identical to those previously found for dog hemoglobin in all respects except one: the αT-13 peptide of coyote has only threonine at residue 130 of the chain. This indicates only one α-chain in coyote instead of two as in dog, which has one α-chain with threonine and one α-chain with alanine at this position. The α-chain from wolf (Canis lupus) is like that from coyote in having only threonine at residue 130.     

Molecular dynamics of sickle and normal hemoglobins

Molecular dynamics (MD) simulations have been carried out for 62.5 ps on crystal structures of deoxy sickle cell hemoglobin (HbS) and normal deoxy hemoglobin (HbA) using the CHARMM MD algorithm, with a time step of 0.001 ps. In the trajectory analysis of the 12.5–62.5 (50 ps) simulation, oscillations of the radius of gyration and solvent-accessible surface area were calculated. HbS exhibited a general contraction during the simulation, while HbA exhibited a nearly constant size. The average deviations of simulated structures from the starting structures were found to be 1.8 Å for HbA and 2.3 Å for HbS. The average rms amplitudes of atomic motions (atomic flexibility) were about 0.7 Å for HbA and about 1.0 Å for HbS. The amplitudes of backbone motion correlate well with temperature factors derived from x-ray crystallography. A comparison of flexibility between the α- and β-chains in both HbA and HbS indicates that the β-chains generally exhibited greater flexibility than the α-chains, and that the HbS β-chains exhibit greater flexibility in the N-terminal and D- and F-helix regions than do those of HbA. The average amplitude of backbone torsional oscillations was about 9°, a value comparable with that of other simulations, with enhanced torsional oscillation occurring primarily at the ends of helices or in loop regions between helices. Comparison of atomic flexibility and torsional oscillation results suggests that the increased β-chain flexibility results from relatively concerted motions of secondary structure elements. The increased flexibility may play an important role in HbS polymerization. Time course analysis of conformational energy of association, hydrogen bonding and hydrophobic bonding (as calculated from solvent accessibility) shows that all three of these factors contribute to the stability of subunit association for both hemoglobins. © 1993 John Wiley & Sons, Inc.     

Primary structure of the hemolglobin β-chain of Rose-ringed Parakeet (Psittacula krameri)

The primary structure of Rose-ringed Parakeet hemoglobin β-chain was established, completing the analysis of this hemoglobin. Comparisons with other avian β-chains show variations smaller than those for the corresponding α-chains. There are 11 amino acid exchanges in relationship to the only other characterized psittaciform β-chain, and a total of 35 positions are affected by differences among all avian β-chains analyzed (versus 61 for the α-chains). At three positions, the Psittacula β-chain has residues unique to this species. Three α₁β₁ contacts are modified, by substitutions at positions β51, β116, and β125.     

19 F-NMR studies of oxygen binding to hemoglobin

The binding of oxygen to hemoglobin has been investigated by ¹⁹F-nuclear magnetic resonance spectroscopy. The ¹⁹F-nmr spectrum of hemoglobin trifluoroacetonylated at cysteine β 93 exhibits chemical shift changes on binding of ligands, which differ depending on which chains are undergoing complexation. Comparison of these changes to the fractional ligation of all chains, determined concurrently from the fractional change in the visible spectrum, shows that initial oxygen molecules bind preferentially to α-chains. The ¹⁹F-nmr spectrum of partially oxygenated hemoglobin contains resonances at the normal chemical shift positions of the oxygenated and deoxy species, in addition to two small resonances at intermediate positions. Analysis of the relativ magnitudes of these four peaks as functions of oxygen pressure permits identification of the intermediate species     

Examination of Haldane's first law for the partition of CO and O2 to hemoglobin A0

A study of the oxygen replacement reaction of carbon monoxide-saturated hemoglobin (HbA₀) was carried out using spectroscopic, calorimetric, and pH titration methods. Under fully saturated conditions the replacement reaction can be defined by a single partition constant over all ratios of bound oxygen to carbon monoxide. This indicates that under saturating conditions Haldane's first law for the ligand binding of gas mixtures holds for any CO/O₂ ratio. It further shows that there is no appreciable difference in relative CO-O₂ affinity between the α- and β-chains. The same partition coefficient was found to hold for different pH, buffer, and allosteric effector conditions. The lack of any pH dependence of the partition coefficient was confirmed by the absence of proton changes for the replacement reaction. The temperature dependence of the partition coefficient and calorimetric results yield a value for the enthalpy of the reaction of ?3.65 ± 0.29 kcal/mol/heme.     

Physical properties of type i collagen in solution: Structure of α-Chains and β- and γ-components and two-component mixtures

The structure of thermally denatured Type I collagen has been studied using laser light scattering. The results indicate that the diffusion coefficients of α-chains and β- and γ-components are 1.550 ± 0.08 × 10^?7, 1.000 ± 0.05 × 10^?7, and 0.835 ± 0.04 × 10^?7 cm²/sec, respectively, at temperatures between 20 and 40°C. It is concluded from diffusion data that these species have hydrodynamic radii of about 13.8 nm (α-chain), 21.5 nm (β-component), and 25.7 nm (γ-component), consistent with previous studies of thermal denaturation by light scattering. It is also concluded, based on volume calculations, that a large volume increase occurs when the triple helix unfolds. Homodyne correlation functions for two component mixtures of α-chains and β-and γ-components appeared to decay exponentially. In all but one case discussed the correlation function could be fitted with a single component having a translational diffusion coefficient which was an intensity weighted average of the diffusion coefficient of each component present.     

Thermodynamics of equilibria of hemoglobins M Milwaukee-I and Saskatoon and isolated chains of hemoglobin a with carbon monoxide

The thermodynamic parameters of the CO-equilibria of isolated chains of hemoglobin A and of two α-chains in hemoglobins M Milwaukee-I and Saskatoon at 25°, pH 7.0 were determined. The parameters for the binding of the first CO molecule to the hemoglobins M were ΔH′=?17 and ?18 kcal/mole heme and ΔS′=?30 and ?29 e.u. for hemoglobins M Milwaukee-I and Saskatoon, respectively. In contrast to this the characteristics of the second step of the binding were ΔH′=+5.9^· and +4.3 kcal/mole and ΔS′=+51 and +49 e.u. These values for the second step were also significantly different from those of the isolated α-chain (ΔH′=?15 kcal/mole and ΔS′=?11 e.u.).     

Hemoglobin of mice with radiation-induced mutations at the hemoglobin loci.

Chemical analyses were done on the abnormal hemoglobins of five (101 × SEC)F₁ offspring of X-irradiated adult SEC mice to determine which hemoglobin genes were expressed in each hemoglobin variant. Three offspring of irradiated SEC males did not express either of the two kinds of α-chains normally found in all SEC mice. The deficient α-chain synthesis caused these mice to exhibit an α-thalassemia similar to human α-thalassemia. Scanning electron microscopy was used to show that many erythrocytes of mice with α-thalassemia have bizarre shapes; e.g. many erthrocytes appeared flattened or had thorny projections (acanthocytes). One mutant with a tandem duplication of a segment of chromosome 7 (site of locus determining β-chain structure) produced twice as much SEC as 101 β-chain polypeptides. One mutant that probably arose by non-disjunction of chromosome 7's in its unirradiated 101 mother and loss of chromosome 7 from the gamete of its irradiated SEC father did not express the SEC β-chain gene.     

Lambda phage cro repressor. DNA sequence-dependent interactions seen by tyrosine fluorescence

The thermodynamics of sickle cell hemoglobin gelation in the presence of oxygen has been investigated by measuring the fractional saturation of the solution and polymer phases, and the solubility. The fractional saturation of the solution phase with oxygen and the solubility were measured by near infrared spectrophotometry after sedimentation of the polymers, while the fractional saturation of the polymer phase was determined from linear dichroism measurements on gels formed by nucleation with an argon ion laser. Using the solution binding data of Gill et al. (1979) to calculate the oxygen pressure corresponding to the solution phase saturation, the initial portion of the polymer binding curve was determined. The self-consistency of the data analysis in terms of the two-phase model for the gel was tested by comparing measured and calculated gel (i.e. solution plus polymer) binding curves, and by comparing the observed solubilities with those calculated from the solution and polymer binding curves using Gibbs-Duhem relations.Oxygen binding to the polymer was found to be non-co-operative up to the maximum measured fractional saturation of 0.14. The binding constant was 0.0059 ± 0.0015 torr^?1 (p₅₀ = 170 ± 40 torr), which is about three times smaller than that of hemoglobin in the low-affinity T quaternary structure. Both the non-co-operative binding and the low affinity could be qualitatively explained in terms of an allosteric model and the current information on the polymer structure.     

High pK value of the N-terminal amino group of the gamma-chain causes low CO2 binding of human fetal hemoglobin.

The N-terminal amino acid residue of the γ-chains of human fetal hemoglobin (Hb F_II) is glycine rather than valine like in many other hemoglobins including the human adult pigment (Hb A). In the course of an evaluation of functional implications associated with this replacement we have studied the CO₂ binding properties of Hb F_II in comparison with Hb F_Ic where the N-termini of the γ-chains are blocked. By comparing Hb F_II and Hb F_Ic it is possible to specifically estimate carbamate formation at the N-termini of the γ-chains in Hb F_II. These data were used to calculate the carbamate equilibrium and ionization constant of these groups. At 37 °C, ?log₁₀ of the ionization constant (pK_z) was found to be 8.1 and is thus significantly higher than pK_z of the N-terminal valines of the β-chains of Hb A which has been reported to be 6.6 at 37 °C. The high pK_z value of the γ-chain α-amino group explains the much lower carbamate formation in Hb F_II compared to Hb A.     

Conservation of globin genes in the “living fossil” Latimeria chalumnae and reconstruction of the evolution of the vertebrate globin family

The (hemo-)globins are among the best-investigated proteins in biomedical sciences. These small heme-proteins play an important role in oxygen supply, but may also have other functions. In addition to well known hemoglobin and myoglobin, six other vertebrate globin types have been identified in recent years: neuroglobin, cytoglobin, globin E, globin X, globin Y, and androglobin. Analyses of the genome of the “living fossil” Latimeria chalumnae show that the coelacanth is the only known vertebrate that includes all eight globin types. Thus, Latimeria can also be considered as a “globin fossil”. Analyses of gene synteny and phylogenetic reconstructions allow us to trace the evolution and the functional changes of the vertebrate globin family. Neuroglobin and globin X diverged from the other globin types before the separation of Protostomia and Deuterostomia. The cytoglobins, which are unlikely to be involved in O₂ supply, form the earliest globin branch within the jawed vertebrates (Gnathostomata), but do not group with the agnathan hemoglobins, as it has been proposed before. There is strong evidence from phylogenetic reconstructions and gene synteny that the eye-specific globin E and muscle-specific myoglobin constitute a common clade, suggesting a similar role in intracellular O₂ supply. Latimeria possesses two α- and two β-hemoglobin chains, of which one α-chain emerged prior to the divergence of Actinopterygii and Sarcopterygii, but has been retained only in the coelacanth. Notably, the embryonic hemoglobin α-chains of Gnathostomata derive from a common ancestor, while the embryonic β-chains – with the exception of a more complex pattern in the coelacanth and amphibians – display a clade-specific evolution. Globin Y is associated with the hemoglobin gene cluster, but its phylogenetic position is not resolved. Our data show an early divergence of distinct globin types in the vertebrate evolution before the emergence of tetrapods. The subsequent loss of globins in certain taxa may be associated with changes in the oxygen-dependent metabolism. This article is part of a Special Issue entitled: Oxygen Binding and Sensing Proteins.     

Conformational and functional properties of hemoglobin in perturbed solvent: Kinetics of O2 release

We studied the kinetics of O₂ release by oxyhemoglobin caused by sodium dithionite, in the presence and in the absence of organic cosolvents (monohydric alcohols and formamide) at 10°C. This study was performed by using standard stopped-flow techniques coupled with microprocessor-based data acquisition. We have fitted the experimental data to a mathematical expression obtained on the basis of a two-state model that takes into account the kinetic heterogeneity between α- and β-chains and the presence of αβ-dimers in oxyhemoglobin solutions. Results indicate that the cosolvents mainly affect the allosteric parameter L, i.e., the T ? R conformational equilibrium of hemoglobin, leaving the intrinsic deoxygenation rates of both R and T states almost unaltered. The L values obtained in the present work are in excellent agreement with analogous values previously estimated from oxygen equilibrium measurements.     

The amino acid sequence of a 27-residue peptide released from the alpha-chain carboxy-terminus during the plasmic digestion of human fibrinogen.

The amino acid sequence of a 27-residue peptide released during the early stages of the plasmin digestion of human fibrinogen has been determined. The corresponding cyanogen bromide fragment has also been isolated from the purified α-chains of fibrinogen, although a separable fraction of those chains lack the fragment, evidently because of $\text{in}$$\text{vivo}$ degradation. The peptide is the carboxy-terminal segment of native α-chains.     

Reaction pathway for the quaternary structure change in hemoglobin

We perform a computer simulation of the quaternary structure change during the allosteric transition of hemoglobin. The simulation is based on a docking procedure by which αβ dimers of human hemoglobin are associated into tetramers after being rotated in various orientations. The stability of tetramers thus reconstituted is estimated from the values of a simplified energy function describing nonbonded interactions and from the area of the surface buried in dimer–dimer contacts (their interface area), which we take to represent stabilizing interactions and solvent contribution. A systematic analysis of tetramers reconstituted with twofold symmetry reveals that when the dimers have the R tertiary structure, only tetramers having R-like quaternary structures are stable. When the dimers have the T tertiary structure, they may associate into T-like tetramers or a variety of quaternary structures ranging from T to near R, thus tracing a plausible reaction pathway for the allosteric transition. We subject intermediates of this pathway to energy refinement with rigid αβ dimers. The refinement demonstrates that symmetrical structures are more stable than non symmetrical ones. A detailed analysis of dimer–dimer contacts in intermediates shows how close packing is maintained over large interfaces throughout the quaternary structure change, especially in the “switch region” of contact between the C helix of α-chains and the FG corner of β-chains.     

Amino acid differences between the α-chains from two hemoglobins of the yellow-cheeked vole (family cricetidae)

The yellow-cheeked vole (Microtus xanthognathus) shows two electrophoretic hemoglobin components. Electrophoresis of the polypeptide chains from the separated hemoglobin components shows identical β-chains but two α-chains of different mobility, α ^f and α ^s . The composition of soluble tryptic peptides was determined for each α-chain. Amino acid differences were found in peptides αT1 and αT9; the compositions of the remainder of the homologous peptides were identical. Differences in αT1, found at α4 (α ^s -Gly-α ^f -Val) and α5 (α ^s -Thr-α ^f -Asp), were confirmed after a run to residue 20 of the fast component in an automatic sequencer. The differences in charge between αT1 peptides can account for the electrophoretic pattern of two hemoglobins. This is the first time that it has been possible to identity the residues which can account for the charge difference between the two hemoglobins observed in a Microtus species.     

Reverse-phase high-performance liquid chromatography of proteins: The separation of hemoglobin chain variants

The potential of reverse-phase high-performance liquid chromatography for the separation of closely related proteins has been investigated. Using an octadecasilyl silica stationary phase and a propanol/pyridine formate solvent system normal α- and β-chains of human hemoglobin have been separated from several of their respective mutant chains which differ by single amino acid residues only. The results suggest that reverse-phase high-performance liquid chromatography is a powerful tool for the separation of medium-sized proteins with minimal structural difference.     

The pK of the amino terminal groups of carbonmonoxy- and deoxyhemoglobin measured by dinitrophenylation in phosphate buffers

The rate of reaction of the terminal valines of the α- and β-chains of hemoglobin with 1-fluoro-2,4-dinitrobenzene was followed spectrophotometrically at 353 nm. The variation with pH of the rate of dinitrophenylation of these groups was measured for both carbonmonoxy- and deoxyhemoglobin. In carbonmonoxyhemoglobin the results indicated a pK near 6.7 and 7.7 for the amino terminal groups of the two kinds of subunils, and were attributed to the α- and β-chains respectively. Removal of ligands produced an increase of 0.1 in both pK values and a decrease of 40% of the pH-independent kinetic constant for dinitrophenylation of the β-subunits. These modifications are due to the conformational changes associated with ligand binding in the system. In phosphate buffers the contribution to the Bohr effect of the amino terminal residues of either chains is negligible.     

Respiration and avoidance reaction of a cyprinid fishPseudogobio esocinus under hypoxia

A cyprinid fish,Pseudogobio esocinus showed gradual bradycardia at oxygen saturation (%) of less than 29.7±4.6 (1.89±0.29 ml/l of oxygen concentration), surfacing at 14.7±1.3 (0.94±0.09ml/l), drastic decrease of oxygen consumption at less than 14.2±0.8 (0.91 ±0.06ml/l) and asphyxia at 9.7±1.4 (0.62±0.09ml/l). The fish avoided water having low oxygen saturation of less than 54.0± 5.4 (3.38±0.30ml/l), and markedly at less than 26.2±3.4 (1.62±0.16 ml/l).     

Oxygen binding of the heme-containing subunits of the extracellular hemoglobin of Lumbricus, terrestris

Fully oxygenated heme-containing subunits of the extracellular hemoglobin of $\text{Lumbricus}\text{,}\text{terrestris}$ were isolated by gel filtration in 0.05 M sodium borate, pH 9.0 at 7 ± 1°C. The polypeptide chain composition of the isolated subunits was determined by SDS PAGE. Most of the subunits exhibited reversible oxygenation curves with oxygen affinities higher than the intact hemoglobin. The Hill plots were nonlinear for $\text{Lumbricus}$ hemoglobin and its subunits: the latter exhibited substantial cooperativities as evidenced by Hill constants at half-saturation in the range 2.0 to 2.8.