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Mark S Hargrove - One of the best experts on this subject based on the ideXlab platform.
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Role of Reversible Histidine Coordination in Hydroxylamine Reduction by Plant Hemoglobins (Phytoglobins)
2016Co-Authors: Navjot Singh Athwal, Jagannathan Alagurajan, Amy H. Andreotti, Mark S HargroveAbstract:Reduction of hydroxylamine to ammonium by phytoglobin, a plant hexacoordinate hemoglobin, is much faster than that of other hexacoordinate Hemoglobins or pentacoordinate Hemoglobins such as myoglobin, leghemoglobin, and red blood cell hemoglobin. The reason for differences in reactivity is not known but could be intermolecular electron transfer between protein molecules in support of the required two-electron reduction, hydroxylamine binding, or active site architecture favoring the reaction. Experiments were conducted with phytoglobins from rice, tomato, and soybean along with human neuroglobin and soybean leghemoglobin that reveal hydroxylamine binding as the rate-limiting step. For hexacoordinate Hemoglobins, binding is limited by the dissociation rate constant for the distal histidine, while leghemoglobin is limited by an intrinsically low affinity for hydroxylamine. When the distal histidine is removed from rice phytoglobin, a hydroxylamine-bound intermediate is formed and the reaction rate is diminished, indicating that the distal histidine imidazole side chain is critical for the reaction, albeit not for electron transfer but rather for direct interaction with the substrate. Together, these results demonstrate that phytoglobins are superior at hydroxylamine reduction because they have distal histidine coordination affinity constants near 1, and facile rate constants for binding and dissociation of the histidine side chain. Hexacoordinate Hemoglobins such as neuroglobin are limited by tighter histidine coordination that blocks hydroxylamine binding, and pentacoordinate Hemoglobins have intrinsically lower hydroxylamine affinities
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Trema and parasponia Hemoglobins reveal convergent evolution of oxygen transport in plants.
Biochemistry, 2010Co-Authors: Ryan Sturms, James T Trent, Smita Kakar, Mark S HargroveAbstract:All plants contain Hemoglobins that fall into distinct phylogenetic classes. The subset of plants that carry out symbiotic nitrogen fixation expresses Hemoglobins that scavenge and transport oxygen to bacterial symbiotes within root nodules. These “symbiotic” oxygen transport Hemoglobins are distinct in structure and function from the nonoxygen transport (“nonsymbiotic”) Hbs found in all plants. Hemoglobins found in two closely related plants present a paradox concerning hemoglobin structure and function. Parasponia andersonii is a nitrogen-fixing plant that expresses a symbiotic hemoglobin (ParaHb) characteristic of oxygen transport Hemoglobins in having a pentacoordinate ferrous heme iron, moderate oxygen affinity, and a relatively rapid oxygen dissociation rate constant. A close relative that does not fix nitrogen, Trema tomentosa, expresses hemoglobin (TremaHb) sharing 93% amino acid identity to ParaHb, but its phylogeny predicts a typical nonsymbiotic hemoglobin with a hexacoordinate heme iron, high ...
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plant Hemoglobins a molecular fossil record for the evolution of oxygen transport
Journal of Molecular Biology, 2007Co-Authors: Julie A Hoy, James T Trent, Smita Kakar, Howard Robinson, Benoit J Smagghe, Mark S HargroveAbstract:The evolution of oxygen transport Hemoglobins occurred on at least two independent occasions. The earliest event led to myoglobin and red blood cell hemoglobin in animals. In plants, oxygen transport "legHemoglobins" evolved much more recently. In both events, pentacoordinate heme sites capable of inert oxygen transfer evolved from hexacoordinate Hemoglobins that have unrelated functions. High sequence homology between hexacoordinate and pentacoordinate Hemoglobins in plants has poised them for potential structural analysis leading to a molecular understanding of this important evolutionary event. However, the lack of a plant hexacoordinate hemoglobin structure in the exogenously ligand-bound form has prevented such comparison. Here we report the crystal structure of the cyanide-bound hexacoordinate hemoglobin from barley. This presents the first opportunity to examine conformational changes in plant hexacoordinate Hemoglobins upon exogenous ligand binding, and reveals structural mechanisms for stabilizing the high-energy pentacoordinate heme conformation critical to the evolution of reversible oxygen binding Hemoglobins.
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human neuroglobin a hexacoordinate hemoglobin that reversibly binds oxygen
Journal of Biological Chemistry, 2001Co-Authors: James T Trent, Richard A. Watts, Mark S HargroveAbstract:Abstract Neuroglobin is a newly discovered mammalian hemoglobin that is expressed predominately in the brain (Burmester, T., Welch, B., Reinhardt, S., and Hankeln, T. (2000) Nature407, 520–523). Neuroglobin has less than 25% identity with other vertebrate globins and shares less than 30% identity with the annelid nerve myoglobin it most closely resembles among known Hemoglobins. Spectroscopic and kinetic experiments with the recombinant protein indicate that human neuroglobin is the first example of a hexacoordinate hemoglobin in vertebrates and is similar to plant and bacterial hexacoordinate Hemoglobins in several respects. The ramifications of hexacoordination and potential physiological roles are explored in light of the determination of an O2 affinity that precludes neuroglobin from functioning in traditional O2 storage and transport.
Roy E Weber - One of the best experts on this subject based on the ideXlab platform.
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the cathodic hemoglobin of anguilla anguilla amino acid sequence and oxygen equilibria of a reverse bohr effect hemoglobin with high oxygen affinity and high phosphate sensitivity
Journal of Biological Chemistry, 1995Co-Authors: Angela Fago, Guido Di Prisco, Vito Carratore, Rene J Feuerlein, Lars Sottrupjensen, Roy E WeberAbstract:As in other fish, the cathodic hemoglobin of the eel Anguilla anguilla is considered to play an important role in oxygen transport under hypoxic and acidotic conditions. In the absence of phosphates this hemoglobin shows a reverse Bohr effect and high oxygen affinity, which is strongly modulated over a wide pH range by GTP (whose concentration in the red blood cells varies with ambient oxygen availability). GTP obliterates the reverse Bohr effect in the cathodic hemoglobin. The molecular basis for the reverse Bohr effect in fish Hemoglobins has remained obscure due to the lack of structural data. We have determined the complete amino acid sequence of the α and β chains of the cathodic hemoglobin of A. anguilla and relate it to the oxygen equilibrium characteristics. Several substitutions in crucial positions are observed compared with other Hemoglobins, such as the replacement of the C-terminal His of the β chain by Phe (that suppresses the alkaline Bohr effect) and of residues at the switch region between α and β subunits (that may alter the allosteric equilibrium, thus causing the high intrinsic oxygen affinity and low cooperativity). The residues binding organic phosphate in the β cleft of fish Hemoglobins are conserved, which explains the strong effect of GTP on oxygen affinity and suggests that these residues contribute to the reverse Bohr effect in the absence of alkaline Bohr groups. Moreover, Hisβ143 that is considered to be responsible for the reverse Bohr effect in human and tadpole Hbs is replaced by Lys.
Guido Di Prisco - One of the best experts on this subject based on the ideXlab platform.
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The Greenland shark Somniosus microcephalus—Hemoglobins and ligand-binding properties
2017Co-Authors: Roberta Russo, Daniela Giordano, Gianluca Paredi, Francesco Marchesani, Lisa Milazzo, Giovanna Altomonte, Pietro Del Canale, Stefania Abbruzzetti, Paolo Ascenzi, Guido Di PriscoAbstract:A large amount of data is currently available on the adaptive mechanisms of polar bony fish Hemoglobins, but structural information on those of cartilaginous species is scarce. This study presents the first characterisation of the hemoglobin system of one of the longest-living vertebrate species (392 ± 120 years), the Arctic shark Somniosus microcephalus. Three major Hemoglobins are found in its red blood cells and are made of two copies of the same α globin combined with two copies of three very similar β subunits. The three Hemoglobins show very similar oxygenation and carbonylation properties, which are unaffected by urea, a very important compound in marine elasmobranch physiology. They display identical electronic absorption and resonance Raman spectra, indicating that their heme-pocket structures are identical or highly similar. The quaternary transition equilibrium between the relaxed (R) and the tense (T) states is more dependent on physiological allosteric effectors than in human hemoglobin, as also demonstrated in polar teleost Hemoglobins. Similar to other cartilaginous fishes, we found no evidence for functional differentiation among the three isoforms. The very similar ligand-binding properties suggest that regulatory control of O2 transport may be at the cellular level and that it may involve changes in the cellular concentrations of allosteric effectors and/or variations of other systemic factors. The Hemoglobins of this polar shark have evolved adaptive decreases in O2 affinity in comparison to temperate sharks.
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blood substitutes
2013Co-Authors: Stefano Bruno, Guido Di Prisco, Stefania Abbruzzetti, Luca Ronda, Cinzia Verde, Andrea MozzarelliAbstract:Background: Conjugation of human and animal Hemoglobins with polyethylene glycol has been widely explored as a means to develop blood substitutes, a novel pharmaceutical class to be used in surgery or emergency medicine. However, PEGylation of human hemoglobin led to products with significantly different oxygen binding properties with respect to the unmodified tetramer and high NO dioxygenase reactivity, known causes of toxicity. These recent findings call for the biotechnological development of stable, low-affinity PEGylated Hemoglobins with low NO dioxygenase reactivity. Results: To investigate the effects of PEGylation on protein structure and function, we compared the PEGylation products of human hemoglobin and Trematomus bernacchii hemoglobin, a natural variant endowed with a remarkably low oxygen affinity and high tetramer stability. We show that extension arm facilitated PEGylation chemistry based on the reaction of T. bernacchii hemoglobin with 2-iminothiolane and maleimido-functionalyzed polyethylene glycol (MW 5000 Da) leads to a tetraPEGylated product, more homogeneous than the corresponding derivative of human hemoglobin. PEGylated T. bernacchii hemoglobin largely retains the low affinity of the unmodified tetramer, with a p50 50 times higher than PEGylated human hemoglobin. Moreover, it is still sensitive to protons and the allosteric effector ATP, indicating the retention of allosteric regulation. It is also 10-fold les
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Low affinity PEGylated hemoglobin from Trematomus bernacchii, a model for hemoglobin-based blood substitutes
BMC Biochemistry, 2011Co-Authors: Daniela Coppola, Guido Di Prisco, Stefania Abbruzzetti, Stefano Bruno, Luca Ronda, Cinzia Verde, Cristiano Viappiani, Andrea MozzarelliAbstract:Background Conjugation of human and animal Hemoglobins with polyethylene glycol has been widely explored as a means to develop blood substitutes, a novel pharmaceutical class to be used in surgery or emergency medicine. However, PEGylation of human hemoglobin led to products with significantly different oxygen binding properties with respect to the unmodified tetramer and high NO dioxygenase reactivity, known causes of toxicity. These recent findings call for the biotechnological development of stable, low-affinity PEGylated Hemoglobins with low NO dioxygenase reactivity. Results To investigate the effects of PEGylation on protein structure and function, we compared the PEGylation products of human hemoglobin and Trematomus bernacchii hemoglobin, a natural variant endowed with a remarkably low oxygen affinity and high tetramer stability. We show that extension arm facilitated PEGylation chemistry based on the reaction of T. bernacchii hemoglobin with 2-iminothiolane and maleimido-functionalyzed polyethylene glycol (MW 5000 Da) leads to a tetraPEGylated product, more homogeneous than the corresponding derivative of human hemoglobin. PEGylated T. bernacchii hemoglobin largely retains the low affinity of the unmodified tetramer, with a p50 50 times higher than PEGylated human hemoglobin. Moreover, it is still sensitive to protons and the allosteric effector ATP, indicating the retention of allosteric regulation. It is also 10-fold less reactive towards nitrogen monoxide than PEGylated human hemoglobin. Conclusions These results indicate that PEGylated Hemoglobins, provided that a suitable starting hemoglobin variant is chosen, can cover a wide range of oxygen-binding properties, potentially meeting the functional requirements of blood substitutes in terms of oxygen affinity, tetramer stability and NO dioxygenase reactivity.
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the cathodic hemoglobin of anguilla anguilla amino acid sequence and oxygen equilibria of a reverse bohr effect hemoglobin with high oxygen affinity and high phosphate sensitivity
Journal of Biological Chemistry, 1995Co-Authors: Angela Fago, Guido Di Prisco, Vito Carratore, Rene J Feuerlein, Lars Sottrupjensen, Roy E WeberAbstract:As in other fish, the cathodic hemoglobin of the eel Anguilla anguilla is considered to play an important role in oxygen transport under hypoxic and acidotic conditions. In the absence of phosphates this hemoglobin shows a reverse Bohr effect and high oxygen affinity, which is strongly modulated over a wide pH range by GTP (whose concentration in the red blood cells varies with ambient oxygen availability). GTP obliterates the reverse Bohr effect in the cathodic hemoglobin. The molecular basis for the reverse Bohr effect in fish Hemoglobins has remained obscure due to the lack of structural data. We have determined the complete amino acid sequence of the α and β chains of the cathodic hemoglobin of A. anguilla and relate it to the oxygen equilibrium characteristics. Several substitutions in crucial positions are observed compared with other Hemoglobins, such as the replacement of the C-terminal His of the β chain by Phe (that suppresses the alkaline Bohr effect) and of residues at the switch region between α and β subunits (that may alter the allosteric equilibrium, thus causing the high intrinsic oxygen affinity and low cooperativity). The residues binding organic phosphate in the β cleft of fish Hemoglobins are conserved, which explains the strong effect of GTP on oxygen affinity and suggests that these residues contribute to the reverse Bohr effect in the absence of alkaline Bohr groups. Moreover, Hisβ143 that is considered to be responsible for the reverse Bohr effect in human and tadpole Hbs is replaced by Lys.
David F. Keren - One of the best experts on this subject based on the ideXlab platform.
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hemoglobin ypsilanti a high oxygen affinity hemoglobin demonstrated by two automated high pressure liquid chromatography systems
American Journal of Clinical Pathology, 2007Co-Authors: Daniel D. Mais, Ronald Gulbranson, Laurence A. Boxer, David F. KerenAbstract:Hemoglobin (Hb) Ypsilanti is a rare high-oxygen-affinity hemoglobin. Like other high-oxygen-affinity Hemoglobins, Hb Ypsilanti manifests as erythrocytosis. Because the migration of many high-oxygen-affinity variants on alkaline and acid gels does not differ from that of HbA, oxygen-hemoglobin dissociation studies are often used to document their presence. Hb Ypsilanti is a notable exception because its electrophoresis pattern on alkaline gel is highly characteristic, exemplifying the phenomenon of hybrid formation in variant Hemoglobins. In the past few years, several laboratories have begun to use high-pressure liquid chromatography (HPLC) as a screen for hemoglobinopathies. We demonstrate the elution profile of Hb Ypsilanti on the 2 most widely used HPLC methods.
James T Trent - One of the best experts on this subject based on the ideXlab platform.
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Trema and parasponia Hemoglobins reveal convergent evolution of oxygen transport in plants.
Biochemistry, 2010Co-Authors: Ryan Sturms, James T Trent, Smita Kakar, Mark S HargroveAbstract:All plants contain Hemoglobins that fall into distinct phylogenetic classes. The subset of plants that carry out symbiotic nitrogen fixation expresses Hemoglobins that scavenge and transport oxygen to bacterial symbiotes within root nodules. These “symbiotic” oxygen transport Hemoglobins are distinct in structure and function from the nonoxygen transport (“nonsymbiotic”) Hbs found in all plants. Hemoglobins found in two closely related plants present a paradox concerning hemoglobin structure and function. Parasponia andersonii is a nitrogen-fixing plant that expresses a symbiotic hemoglobin (ParaHb) characteristic of oxygen transport Hemoglobins in having a pentacoordinate ferrous heme iron, moderate oxygen affinity, and a relatively rapid oxygen dissociation rate constant. A close relative that does not fix nitrogen, Trema tomentosa, expresses hemoglobin (TremaHb) sharing 93% amino acid identity to ParaHb, but its phylogeny predicts a typical nonsymbiotic hemoglobin with a hexacoordinate heme iron, high ...
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plant Hemoglobins a molecular fossil record for the evolution of oxygen transport
Journal of Molecular Biology, 2007Co-Authors: Julie A Hoy, James T Trent, Smita Kakar, Howard Robinson, Benoit J Smagghe, Mark S HargroveAbstract:The evolution of oxygen transport Hemoglobins occurred on at least two independent occasions. The earliest event led to myoglobin and red blood cell hemoglobin in animals. In plants, oxygen transport "legHemoglobins" evolved much more recently. In both events, pentacoordinate heme sites capable of inert oxygen transfer evolved from hexacoordinate Hemoglobins that have unrelated functions. High sequence homology between hexacoordinate and pentacoordinate Hemoglobins in plants has poised them for potential structural analysis leading to a molecular understanding of this important evolutionary event. However, the lack of a plant hexacoordinate hemoglobin structure in the exogenously ligand-bound form has prevented such comparison. Here we report the crystal structure of the cyanide-bound hexacoordinate hemoglobin from barley. This presents the first opportunity to examine conformational changes in plant hexacoordinate Hemoglobins upon exogenous ligand binding, and reveals structural mechanisms for stabilizing the high-energy pentacoordinate heme conformation critical to the evolution of reversible oxygen binding Hemoglobins.
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human neuroglobin a hexacoordinate hemoglobin that reversibly binds oxygen
Journal of Biological Chemistry, 2001Co-Authors: James T Trent, Richard A. Watts, Mark S HargroveAbstract:Abstract Neuroglobin is a newly discovered mammalian hemoglobin that is expressed predominately in the brain (Burmester, T., Welch, B., Reinhardt, S., and Hankeln, T. (2000) Nature407, 520–523). Neuroglobin has less than 25% identity with other vertebrate globins and shares less than 30% identity with the annelid nerve myoglobin it most closely resembles among known Hemoglobins. Spectroscopic and kinetic experiments with the recombinant protein indicate that human neuroglobin is the first example of a hexacoordinate hemoglobin in vertebrates and is similar to plant and bacterial hexacoordinate Hemoglobins in several respects. The ramifications of hexacoordination and potential physiological roles are explored in light of the determination of an O2 affinity that precludes neuroglobin from functioning in traditional O2 storage and transport.