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1.
M J McDonald R W Noble V S Sharma H M Ranney J H Crookston J M Schwartz 《Journal of molecular biology》1975,94(2):305-310
Lepore hemoglobins result from crossovers between normal beta and delta chain genes. Structural investigation of two newly discovered examples of Lepore hemoglobins revealed one of them to be structurally identical to hemoglobin Lepore Hollandia α2Aδ22 -x- β50, a rarely occurring Lepore variant, while the second had the structure of hemoglobin Lepore Boston α2Aδ87 -x- β116. Studies of the equilibrium and kinetic properties of the liganding reactions of these two Lepore hemoglobins, which differ only in three amino acid residues, and comparison of these with the known properties of hemoglobin A1 (α2β2) and hemoglobin A2 (α2δ2) have been carried out. A high value of n, the Hill coefficient, indicating normal heme-heme interaction, was observed in each hemoglobin along with a normal Bohr effect. However, a slight but definite increase in oxygen affinity was observed for each Lepore hemoglobin. Furthermore, kinetic studies indicated a slight but consistently increased rate of ligand combination and a somewhat decreased rate of oxygen dissociation for hemoglobins Lepore Hollandia and Lepore Boston at pH 7 and 20 °C. Apparently, the higher oxygen affinity of these Lepore hemoglobins over those of the normal hemoglobins A1 and A2 reflects changes of sequence that are common to both types of hemoglobin Lepore. 相似文献
2.
The structure and function of plant hemoglobins. 总被引:1,自引:0,他引:1
Plants, like humans, contain hemoglobin. Three distinct types of hemoglobin exist in plants: symbiotic, non-symbiotic, and truncated hemoglobins. Crystal structures and other structural and biophysical techniques have revealed important knowledge about ligand binding and conformational stabilization in all three types. In symbiotic hemoglobins (leghemoglobins), ligand binding regulatory mechanisms have been shown to differ dramatically from myoglobin and red blood cell hemoglobin. In the non-symbiotic hemoglobins found in all plants, crystal structures and vibrational spectroscopy have revealed the nature of the structural transition between the hexacoordinate and ligand-bound states. In truncated hemoglobins, the abbreviated globin is porous, providing tunnels that may assist in ligand binding, and the bound ligand is stabilized by more than one distal pocket residue. Research has implicated these plant hemoglobins in a number of possible functions differing among hemoglobin types, and possibly between plant species. 相似文献
3.
The antigenic properties of a number of chromatographically purified primate hemoglobins were compared to those of normal human hemoglobin using a sensitive radioimmunochemical procedure. The degree of inhibition of the antigen-antibody reaction with heterologous hemoglobins appeared to be related to the structural similarity of these proteins to the normal human hemoglobin immunogen. With the exception of the baboon hemoglobin, the antigenicity of the hemoglobins paralleled the phylogeny of the primates. The gorilla and chimpanzee hemoglobins were antigenically identical to normal human hemoglobin, whereas the gibbon and orangutan hemoglobins were substantially more variable. Of the Old World monkey hemoglobins examined, the baboon produced lower inhibition values, suggesting a greater degree of structural dissimilarity than other Cercopithecoidea hemoglobins, which is compatible with a greater rate of evolutionary change occurring in this protein. Using the known amino acid sequences of human and other primate hemoglobins, we have attempted to identify antigenic determinant areas of the proteins. 相似文献
4.
Nine hemoglobins were purified from blood of Salmo clarki by ion-exchange chromatography and preparative isoelectric focusing. The subunit structures of eight of the purified hemoglobins were studied by electrophoresis of globins in the presence of urea. Six are alpha 2 beta 2 tetramers while two appear to be heterotetramers of the type alpha alpha' beta 2 and alpha alpha' beta beta'. The effects of pH, nucleotides, and temperature on the oxygen equilibria of the purified hemoglobins were studied. Five hemoglobins with isoelectric points from 9.1 to 7.1 and one minor hemoglobin with an isoelectric point of 5.9 appear to have essentially identical oxygen binding properties. All have similar oxygen equilibria which are independent of pH and temperature and not affected by saturating amounts of ATP. Another minor hemoglobin with an isoelectric point below 5.9 has similar oxygen equilibria except for a possible pH dependence. Two hemoglobins, with isoelectric points of 6.5 and 6.4, have oxygen binding properties which are strongly pH and temperature dependent. Addition of ATP or GTP causes a large decrease in the oxygen affinity without affecting the cooperativity of oxygen binding. The effect of GTP is slightly greater than that of ATP. No significant differences were observed in the oxygen equilibria of these two hemoglobins. The red blood cells of S. clarki were found to contain large amounts of both ATP and GTP, with an ATP:GTP ratio of 3:1. Both nucleotides may be important modulators of hemoglobin oxygen affinity in S. clarki, in contrast to the situation in S. gairdneri, in which red blood cell GTP concentrations are considerably lower. The presence of six or possibly seven hemoglobins with identical oxygen binding properties in S. clarki suggests that, to a large extent, the physiological role of multiple hemoglobins in this species involves phenomena not directly related to the oxygen binding properties of the hemoglobins. 相似文献
5.
Asymmetrical hybrid hemoglobins formed from mixtures of two structurally different hemoglobins were found to be readily separated by cation-exchange high-performance liquid chromatography under anaerobic conditions. When oxyhemoglobins A and S were mixed and deoxygenated, the resulting HPLC chromatogram showed three peaks. The distribution of the three components follow the binomial expansion a2 + 2 ab + b2 = 1, where a and b are the initial fractions of parent hemoglobins. The middle peak was collected in a test tube saturated with CO gas and reanalyzed under the same experimental conditions. This middle component gave two peaks of equal areas with retention times identical to those of the CO-form of the parent hemoglobins without the appearance of the hybrid hemoglobin band. No intermediate peak was observed in solutions of mixtures of liganded hemoglobins under aerobic conditions. Hybrid hemoglobins AC and SC were also formed when oxyhemoglobins A and C, S and C were mixed, respectively. The separation and the identification of hemoglobins and hybrid hemoglobin employing cation-exchange HPLC can be achieved within 30 min by gradient elution. In addition, the ability to isolate hybrid hemoglobins may be a valuable tool for the study of physical and chemical properties of hybrid hemoglobins. 相似文献
6.
Asymmetrical hybrid hemoglobins formed in mixtures of Hb A and Hb S, Hb F and Hb S, Hb S and Hb York(beta 146 His----Pro), and Hb A and Hb York were separated by high performance liquid chromatography on cation and anion exchange columns under anaerobic conditions. The ratio of the hybrid hemoglobin to the total mixture was consistently lower than that theoretically expected and decreased with longer elution times. The hybrid tetramer appears to be unstable even under anaerobic conditions and dissociates into alpha beta dimers. The time course of dissociation of the hybrid hemoglobins was determined by varying the separation programs and thus separating the hybrid hemoglobin at different elution times. The rate of the dissociation of the hybrid hemoglobins studied follows first order kinetics. The lines representing the time course of dissociation of hybrid hemoglobins were extrapolated to time 0 to determine the fraction of the hybrid hemoglobin in the mixture prior to separation. The values obtained for equimolar mixtures of Hb A and Hb S and Hb York and Hb S or Hb A were in agreement with the expected theoretical value (50%). In contrast, the value obtained for hybrid hemoglobin FS was slightly less (about 40%). AY and SY hybrid hemoglobins dissociated into dimers at a considerably faster rate than did AS and FS hybrid hemoglobins, possibly because of the mutation at the beta 146-position in hybrid hemoglobins containing alpha beta Y dimers. This mutation hinders the formation of salt bridges that normally stabilize the "T" quaternary conformation. Since such hybrid hemoglobins have a partial "R" conformation even when deoxygenated, their rate of dissociation to dimers is expected to increase. 相似文献
7.
The tetramer-dimer dissociation equilibria (K 4,2) of several fish hemoglobins have been examined by sedimentation velocity measurements with a scanner-computer system for the ultracentrifuge and by flash photolysis measurements using rapid kinetic methods. Samples studied in detail included hemoglobins from a marine teleost, Brevoortia tyrannus (common name, menhaden); a fresh water teleost, Cyprinus carpio, (common name, carp); and an elasmobranch Prionace glauca (common name, blue shark). For all three species in the CO form at pH 7, in 0.1 M phosphate buffer, sedimentation coefficients of 4.3 S (typical of tetrameric hemoglobin) are observed in the micromolar concentration range. In contrast, mammalian hemoglobins dissociate appreciably to dimers under these conditions. The inability to detect dissociation in three fish hemoglobins at the lowest concentrations examined indicates that K 4,2 must have a value of 10(-8) M or less. In flash photolysis experiments on very dilute solutions in long path length cells, two kinetic components were detected with their proportions varying as expected for an equilibrium between tetramers (the slower component) and dimers (the faster component); values of K 4,2 for the three fish hemoglobins in the range 10(-9) to 10(-8) M were calculated from these data. Thus, the values of K 4,2 for liganded forms of the fish hemoglobins appear to be midway between the value for liganded human hemoglobin (K 4,2 approximately 10(-6) M) and unliganded human hemoglobin (K 4,2 approximately 10(-12) M). This conclusion is supported by measurements on solutions containing guanidine hydrochloride to enhance the degree of dissociation. All three fish hemoglobins are appreciably dissociated at guanidine concentrations of about 0.8 M, which is roughly midway between the guanidine concentrations needed to cause comparable dissociation of liganded human hemoglobin (about 0.4 M) and unliganded human hemoglobin (about 1.6 M). Kinetic measurements on solutions containing guanidine hydrochloride indicated that there are changes in both the absolute rates and the proportions of the fast and slow components, which along with other factors complicated the analysis of the data in terms of dissociation constants. Measurements were also made in solutions containing urea to promote dissociation, but with this agent very high concentrations (about 6 M) were required to give measureable dissociation and the fish hemoglobins were unstable under these conditions, with appreciable loss of absorbance spectra in both the sedimentation and kinetic experiments. 相似文献
8.
B Giardina F Arevalo M E Clementi L Ferrara A Di Luccia E Lendaro A Bellelli S G Condò 《European journal of biochemistry》1992,204(2):509-513
The ligand-binding properties of hemoglobins from two homozygote phenotypes (AA and BB) of water buffalo (Bubalus bubalis) have been characterized by equilibrium and kinetic techniques. In the case of the BB phenotype, the two constituent hemoglobins have been purified and separately analysed. Buffalo hemoglobins display the reduced sensitivity to organic phosphates characteristic of ruminant hemoglobins, their physiological effector probably being the chloride ion. In contrast to the other known hemoglobins from ruminants, all the hemoglobins from the water buffalo display a significant temperature sensitivity, the delta H for oxygen binding in the presence of physiological effectors approaching that of human hemoglobin (delta H = -30.5 kJ/mol O2). This discrepancy with the other ruminant hemoglobins (e.g. ox, delta H = -10.4 kJ/mol O2), whose primary structure is very similar to that of buffalo, hemoglobins might be correlated to the different habitat and phylogenetic history of the two subfamilies (Bos and Bubalus) of Bovidae. 相似文献
9.
The biological functions of heme proteins are linked to their rate and affinity constants for ligand binding. Kinetic experiments are commonly used to measure equilibrium constants for traditional hemoglobins comprised of pentacoordinate ligand binding sites and simple bimolecular reaction schemes. However, kinetic methods do not always yield reliable equilibrium constants with more complex hemoglobins for which reaction mechanisms are not clearly understood. Furthermore, even where reaction mechanisms are clearly understood, it is very difficult to directly measure equilibrium constants for oxygen and carbon monoxide binding to high-affinity (K(D) < 1 micro M) hemoglobins. This work presents a method for direct measurement of equilibrium constants for high-affinity hemoglobins that utilizes a competition for ligands between the "target" protein and an array of "scavenger" hemoglobins with known affinities. This method is described for oxygen and carbon monoxide binding to two hexacoordinate hemoglobins: rice nonsymbiotic hemoglobin and Synechocystis hemoglobin. Our results demonstrate that although these proteins have different mechanisms for ligand binding, their affinities for oxygen and carbon monoxide are similar. Their large affinity constants for oxygen, 285 and approximately 100 micro M(-1) respectively, indicate that they are not capable of facilitating oxygen transport. 相似文献
10.
- 1.1. Antisera produced in rabbits by immunization with vascular hemoglobins of the earthworm Lumbricus terrestris and horseleech Haemopsis marmorata were tested for the ability to cross-react with heterologous hemoglobin.
- 2.2.Two of eight antisera demonstrated immunological cross-reactivity between the hemoglobins studied.
- 3.3.The structural basis for this cross-reactivity is briefly considered.
11.
L P Stratton L K Duffy A S Porchet 《Comparative biochemistry and physiology. B, Comparative biochemistry》1977,56(3):321-327
1. The electrophoretic mobilities of the hemoglobins of 7 taxa of microtines were compared. Microtus oeconomus, M. pennsylvanicus pullatus and M. xanthognatus showed identical 2-band patterns on electrophoresis of their hemoglobins while M. pennsylvanicus tananaensis showed only a single hemoglobin corresponding to the major band of the others. Dicrostonyx rubricatus and D. stevensoni exhibited identical patterns different from the Microtus species. Lemmus sibiricus had a slow hemoglobin component with mobility slightly different from the slow ones of the Microtus species while the fast component appeared the same. 2. Electrophoresis of individual globin chains from hemolysates, purified hemoglobins, and isolated chains indicated a large degree of similarity between the species studied, although there were significant differences in hemoglobin patterns. 3. The minor hemoglobin band in Microtus seems to be the result of a second alpha chain locus as determined from the hemoglobins from hybrids of two subspecies. 4. Salting-out studies indicated differences between hemoglobins that were not detectable by electrophoresis of either whole hemoglobins or isolated chains. 5. M. xanthognathus hemolysate was considerably less soluble than those of M. oeconomus and M. pennsylvanicus pullatus which had essentially the same solubility. 6. The major hemoglobin components of M. pennsylvanicus pullatus and M. xanthognathus were considerably less soluble than either the corresponding unfractionated hemolysates or purified minor components. 相似文献
12.
Oxygen equilibrium study and light absorption spectra of Ni(II)-Fe(II) hybrid hemoglobins 总被引:1,自引:0,他引:1
Ni(II)-Fe(II) hybrid hemoglobins, in which hemes in either the alpha or beta subunit are substituted with Ni(II) protoporphyrin IX, have been prepared and characterized. Since Ni(II) protoporphyrin IX binds neither oxygen nor carbon monoxide, the oxygen equilibrium properties of the Fe subunit in these hybrid hemoglobins were specifically determined. K1 values, namely the equilibrium constants for the first oxygen molecule to bind to hemoglobin, agreed well for these hybrid hemoglobins with the K1 value of native hemoglobin A in various conditions. Therefore, Ni(II) protoporphyrin IX in these hybrid hemoglobins behaves like a permanently deoxygenated heme. Both Ne-Fe hybrid hemoglobins bound oxygen non-co-operatively at low pH values. When the pH was raised, alpha 2 (Fe) beta 2 (Ni) showed co-operativity, but the complementary hybrid, alpha 2 (Ni) beta 2 (Fe), did not show co-operativity even at pH 8.5. The light absorption spectra of Ni(II)-Fe(II) hybrid hemoglobins indicated that the coordination states of Ni(II) protoporphyrin IX in the alpha subunits responded to the structure of the hybrid, whereas those in the beta subunits were hardly changed. In a deoxy-like structure (the structure that looks like that observed in deoxyhemoglobin), four-co-ordinated Ni(II) protoporphyrin IX was dominant in the alpha (Ni) subunits, while under the conditions that stabilized an oxy-like structure (the structure that looks like that observed in oxyhemoglobin), five-co-ordinated Ni(II) protoporphyrin IX increased. The small change observed in the absorption spectrum of the beta (Ni) subunits is not related to the change of the co-ordination number of Ni(II) protoporphyrin IX. Non-co-operative binding of oxygen to the beta subunits in alpha 2 (Ni) beta 2 (Fe) accompanied the change of absorption spectrum in the alpha (Ni) subunits. We propose a possible interpretation of this unique feature. 相似文献
13.
CD studies on the reversed heme orientation in monomeric Glycera dibranchiata hemoglobins 总被引:1,自引:0,他引:1
R Santucci J Mintorovitch I Constantinidis J D Satterlee F Ascoli 《Biochimica et biophysica acta》1988,953(2):201-204
Circular dichroism spectra of three monomeric components of Glycera dibranchiata hemoglobins are reported. Contrary to what is found for most hemoglobins and myoglobins, G. dibranchiata hemoglobins display largely negative dichroic spectra in the Soret region. Independent NMR measurements have shown that the same monomeric hemoglobin components contain the heme moiety predominantly (greater than 85%) oriented in a reversed way with respect to the orientation which occurs in most hemoglobins and myoglobins. On the basis of these independent NMR studies, and also of previous data on other invertebrate hemoproteins, a correlation appears evident between reversed heme orientation in hemoglobins and negative ellipticity in the Soret CD spectrum. This represents a simple tool to evaluate this aspect of heme asymmetric environment. 相似文献
14.
15.
The heme prosthetic group in hemoglobins is most often attached to the globin through coordination of either one or two histidine side chains. Those proteins with one histidine coordinating the heme iron are called "pentacoordinate" hemoglobins, a group represented by red blood cell hemoglobin and most other oxygen transporters. Those with two histidines are called "hexacoordinate hemoglobins", which have broad representation among eukaryotes. Coordination of the second histidine in hexacoordinate Hbs is reversible, allowing for binding of exogenous ligands like oxygen, carbon monoxide, and nitric oxide. Research over the past several years has produced a fairly detailed picture of the structure and biochemistry of hexacoordinate hemoglobins from several species including neuroglobin and cytoglobin in animals, and the nonsymbiotic hemoglobins in plants. However, a clear understanding of the physiological functions of these proteins remains an elusive goal. 相似文献
16.
In response to oxygen limitation or oxidative and nitrosative stress, bacteria express three kinds of hemoglobin proteins: truncated hemoglobins (tr Hbs), hemoglobins (Hbs) and flavohemoglobins (flavo Hbs). The two latter groups share a high sequence homology and structural similarity in their globin domain. Flavohemoglobin proteins contain an additional reductase domain at their C-terminus and their expression is induced in the presence of reactive nitrogen and oxygen species. Flavohemoglobins detoxify NO in an aerobic process, termed nitric oxide dioxygenase reaction, which protects the host from various noxious nitrogen compounds. Only a small number of bacteria express hemoglobin proteins and the best studied of these is from Vitreoscilla sp. Vitreoscilla hemoglobin (VHb) has been expressed in various heterologous hosts under oxygen-limited conditions and has been shown to improve growth and productivity, rendering the protein interesting for biotechnology industry. The close interaction of VHb with the terminal oxidases has been shown and this interplay has been proposed to enhance respiratory activity and energy production by delivering oxygen, the ultimate result being an improvement in growth properties. 相似文献
17.
Miranda JL 《Biochemical and biophysical research communications》2006,343(3):924-927
A group of single-domain proteins in Bacteria similar to thermoglobin, an oxygen-avid hemoglobin representative of the ancestral form, reveals the primordial structure, function, and evolvability of the family. Conserved residues at specific positions function to bind ligand or participate in hydrophobic packing of the protein core during protein folding. A potential hydrogen bond network consisting of a tyrosine and glutamine residue in the distal ligand-binding site of most hemoglobins suggests that the ancestral protein bound oxygen avidly. Two divergent hemoglobins with mutations at generally conserved positions contain non-canonical ligand-binding sites, illustrating plasticity of the fold. One binds heme in a manner similar to cytochromes and may represent an evolutionary link to the precursor of the hemoglobin fold. Conservation suggests specific biochemical properties of the ancestral protein; diversity suggests an evolvability of this group of hemoglobins tolerant of mutations that perturb conserved biochemical properties for adaptation to novel functions. 相似文献
18.
S C Wong T H Huisman 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1975,150(3):581-584
Sickling, viscosity and gelling properties of the red cells and the hemoglobins of three Virginia white-tailed deer homozygous for types II and III (the sickling types) and V (the nonsickling type), respectively, have been analyzed. The sickling of erythrocytes of deer with type II or III is inhibited by urea and cyanate at concentrations which are comparable to those used in in vitro studies of red cells from patients with sickle cell anemia. No differences were observed between the viscosities of the three deer hemoglobin types at temperatures of 12 degrees C or above. High concentrations of deer hemoglobin types II and III gelled at 1 degree C and at pH values of 7.4-7.7; the minimum gelling concentration of type II was 33.5 g% and of type III was 38 g%. Gel formation was not observed at pH values between 6.7-7.1. Hemoglobin type V did not gel and prevented the formation of gels of type II and III in mixtures at pH 7.6-7.7. 相似文献
19.
John J. Just Josef Schwager Rudolf Weber Hans Fey Hedi Pfister 《Development genes and evolution》1980,188(1):75-80
Summary Antisera against larval and adultXenopus hemoglobins as well as adult human hemoglobin showed no cross-reaction when tested by immunodiffusion against each heterologous antigen. In this test hemoglobin of a single animal produced two precipitation lines for larvae, but only one for adult stages. Immunoelectrophoresis also revealed more complex precipitation patterns for larval than for adult hemoglobins. Hemoglobin of the isogenic hybrid cloneXenopus laevis/X. gilli also reacted with antisera against normalXenopus hemoglobin.Quantitation of hemoglobins, analyzed by radial immunodiffusion showed fewer than 1% of adult hemoglobin in red cells of larvae, but 30% at completion of metamorphosis. Two weeks later adult hemoglobin attained over 90%, and in red cells of adultXenopus an average of 1% larval hemoglobin were detected.The relatively short transition period suggests that the loss of larval hemoglobin may be due to the elimination of larval red cells, and that the increase in adult hemoglobin may be indicative of a new cell line. 相似文献
20.
Separation of asymmetrical hybrid containing hemoglobin F by anaerobic anion-exchange high-performance liquid chromatography 总被引:1,自引:0,他引:1
Asymmetrical hybrid hemoglobins formed from mixtures of oxyhemoglobins S and F and A and F were separated by high-performance liquid chromatography on a 4.6 X 250 mm wide-pore polyethyleneimine-silica gel column under anaerobic conditions. The resulting HPLC chromatogram showed three peaks, with the middle peak representing the hybrid hemoglobin. The areas of these three peaks were quantified and the amount of hybrids formed was less than that predicted theoretically. We found that the deviation was due to the equilibrium constant of the FS hybrid hemoglobin differing from that of the parent hemoglobins. In this report, we introduce the anaerobic recycle ion-exchange HPLC method to determine the rate of dissociation of AS and FS hybrid hemoglobins at constant pH buffer conditions. The results obtained by this method demonstrate that FS hybrid hemoglobin is more unstable than AS hybrid hemoglobin. The free energy of association for asymmetrical hybrids containing hemoglobin F is approximately 0.6 Kcal/mol greater than that of the symmetrical parent hemoglobins. 相似文献