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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.
T M S Chang - One of the best experts on this subject based on the ideXlab platform.
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modified Hemoglobin based blood substitutes crosslinked recombinant and encapsulated Hemoglobin
Vox Sanguinis, 1998Co-Authors: T M S ChangAbstract:Native Hemoglobin in the form of stroma-free Hemoglobin cannot be used as blood substitute. Hemoglobin has to be modified either molecularly or encapsulated. First generation molecularly modified ultrapure Hemoglobins are now in clinical trial - some in Phase III. There are a number of these. Poly.Hemoglobin is formed by crosslinking Hemoglobin molecules intermolecularly and intramolecularly. A crosslinked single Hemoglobin molecule is formed by crosslinking Hemoglobin intramolecularly. Recombinant Hemoglobin from E.coli is formed by fusion of the subunits of each Hemoglobin molecule. Conjugated Hemoglobin is formed by crosslinking each Hemoglobin molecule to soluble polymers. A second generation system formed by crosslinking Hemoglobin-superoxide dismutase-catalase is being developed. A third generation Hemoglobin-based blood substitute is based on microencapsulated Hemoglobin, artificial red blood cells, that more closely resemble a complete red blood cell.
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modified Hemoglobin blood substitutes present status and future perspectives
Biotechnology annual review, 1998Co-Authors: T M S ChangAbstract:Abstract Biotechnological techniques of cross-linking and microencapsulation of Hemoglobin result in blood substitutes that can replace red blood cells. Unlike red blood cells they can be sterilized by pasteurization, ultrafiltration and chemical means. This removes microorganisms responsible for AIDS, hepatitis, etc. Since they are free of red blood cell blood group antigens, there is no need for cross-matching or typing. This saves time and facilities and allows on-the-spot transfusion such as the infusion of salt solution. Furthermore, they can be stored for a long time. Hemoglobin for modification can be extracted from human red blood cells. Other sources of Hemoglobin include bovine Hemoglobin and recombinant human Hemoglobin. Clinical trials are ongoing testing the possible uses of cross-linked Hemoglobin in cardiac, orthopedic, trauma and other types of surgery. It is also being tested for the replacement of lost blood in severe bleeding due to trauma or other causes. Cross-linked Hemoglobins are first generation blood substitutes that only fulfil some of the functions of red blood cells. New generations of more complete red blood cell substitutes are being developed. These include cross-linked Hemoglobin-catalase-superoxide dismutase and microencap-sulated Hemoglobin-enzyme systems.
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blood substitutes based on modified Hemoglobin prepared by encapsulation or crosslinking an overview
Biomaterials artificial cells and immobilization biotechnology : official journal of the International Society for Artificial Cells and Immobilization, 1992Co-Authors: T M S ChangAbstract:Modified Hemoglobin consists of (1) encapsulated Hemoglobin and (2) cross-linked Hemoglobin (polyHemoglobin, intramolecularly cross-linked Hemoglobin and conjugated Hemoglobin). There have been new advances in all types of modified Hemoglobins. Modified Hemoglobins are effective in hemorrhagic shock. However, it is important to define hemorrhagic shock models and experimental designs. Important progress has been made in research on vasoactivities, organ perfusion, organ preservation, biodistribution, hematology, complement activation immunology and other areas. A preclinical screening test may bridge the gap between animal safety studies and injection into human. Potential new sources of Hemoglobin included bovine Hemoglobin, recombinant human Hemoglobin and synthetic heme.
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.
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.
Stuart A Chalew - One of the best experts on this subject based on the ideXlab platform.
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two dimensional analysis of glycated Hemoglobin heterogeneity in pediatric type 1 diabetes patients
Analytical Biochemistry, 2013Co-Authors: James M Hempe, And Michael D Mcgehee, Stuart A ChalewAbstract:Interindividual and ethnic variation in glycated Hemoglobin levels, unrelated to blood glucose variation, complicates the clinical use of glycated Hemoglobin assays for the diagnosis and management of diabetes. Assessing the types and amounts of glycated Hemoglobins present in erythrocytes could provide insight into the mechanism. Blood samples and self-monitored mean blood glucose (MBG) levels were obtained from 85 pediatric type 1 diabetes patients. Glycated Hemoglobin levels were measured using three primary assays (boronate-affinity chromatography, capillary isoelectric focusing (CIEF), and standardized DCA2000+ immunoassay) and a two-dimensional (2D) analytical system consisting of boronate-affinity chromatography followed by CIEF. The 2D system separated Hemoglobin into five subfractions, four of which contained glycated Hemoglobins. Glycated Hemoglobin measurements were compared in patients with low, moderate, or high Hemoglobin glycation index (HGI), a measure of glycated Hemoglobin controlled for blood glucose variation. MBG was not significantly different between HGI groups. Glycated Hemoglobin levels measured by all three primary assays and in all four glycated 2D subfractions were significantly different between HGI groups and highest in high HGI patients. These results show that interindividual variation in glycated Hemoglobin levels was evident in diabetes patients with similar blood glucose levels regardless of which glycated Hemoglobins were measured.
