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Tsuneshige A, Tokoro T. Cooperative oxygen binding in beta-semihemoglobins caused by a chemical modification in the alpha1beta1 interface. J Inorg Biochem 2023; 246:112264. [PMID: 37290360 DOI: 10.1016/j.jinorgbio.2023.112264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 04/25/2023] [Accepted: 05/20/2023] [Indexed: 06/10/2023]
Abstract
A beta-semihemoglobin is an alpha-beta dimer of hemoglobin (Hb) in which the beta-subunit carries heme, while the alpha-subunit is heme-less, in apo form. It is characterised by displaying a high affinity for oxygen, and absence of cooperative binding of oxygen. We have modified chemically the residue beta112Cys (G14), located adjacent to the alpha1beta1 interface, and studied the impact of such a modification on the oligomeric state and oxygenation properties of the derivatives. We also studied the impact of modifying beta93Cys (F9) since its modification was unavoidable. For this, we used N-Ethyl maleimide and iodoacetamide. For the alkylation of beta112Cys (G14) in isolated subunits, we used N-Ethyl maleimide, iodoacetamide, or additionally, 4,4'-Dithiopyridine. Seven native and chemically modified beta-subunit derivatives were prepared and analysed. Only those derivatives treated with iodoacetamide showed oxygenation properties that were indistinguishable from those of native beta-subunits. These derivatives were then converted into their respective semihemoglobin forms, and four additional derivatives were prepared and analysed .in terms of ligation-linked oligomeric state, and oxygenation function, and contrasted against native Hb and unmodified beta-subunits. Strikingly, beta-semiHbs with modifications in beta112Cys showed indications of cooperative oxygen binding in various degrees, which suggested the possibility of assembly of two beta-semiHbs. The derivative modified with 4-Thiopyridine in beta112Cys showed a highly cooperative binding of oxygen (nmax = 1.67). A plausible allosteric scheme that could explain allostery in beta-semiHb system is suggested.
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Affiliation(s)
- Antonio Tsuneshige
- Department of Frontier Bioscience, Faculty of Bioscience and Applied Chemistry, Hosei University, Tokyo 184-8584, Japan; Research Center for Micro-Nano Technology, Hosei University, Tokyo 184-0003, Japan.
| | - Tatsunori Tokoro
- Department of Frontier Bioscience, Faculty of Bioscience and Applied Chemistry, Hosei University, Tokyo 184-8584, Japan
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2
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Nagatomo S, Saito K, Yamamoto K, Ogura T, Kitagawa T, Nagai M. Heterogeneity between Two α Subunits of α2β2 Human Hemoglobin and O2 Binding Properties: Raman, 1H Nuclear Magnetic Resonance, and Terahertz Spectra. Biochemistry 2017; 56:6125-6136. [DOI: 10.1021/acs.biochem.7b00733] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Shigenori Nagatomo
- Department
of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
| | - Kazuya Saito
- Department
of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
| | - Kohji Yamamoto
- Research
Center for Development of Far-Infrared Region, University of Fukui, Fukui, Fukui 910-8507, Japan
| | - Takashi Ogura
- Picobiology
Institute, Graduate School of Life Science, University of Hyogo, RSC-UH Leading
Program Center, Sayo, Sayo-gun, Hyogo 679-5148, Japan
| | - Teizo Kitagawa
- Picobiology
Institute, Graduate School of Life Science, University of Hyogo, Kouto, Kamigori, Ako-gun, Hyogo 678-1297, Japan
| | - Masako Nagai
- Research
Center for Micro-Nano Technology, Hosei University, Koganei, Tokyo 184-0003, Japan
- School
of
Health Sciences, College of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Ishikawa 920-0942, Japan
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3
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Nagatomo S, Okumura M, Saito K, Ogura T, Kitagawa T, Nagai M. Interrelationship among Fe-His Bond Strengths, Oxygen Affinities, and Intersubunit Hydrogen Bonding Changes upon Ligand Binding in the β Subunit of Human Hemoglobin: The Alkaline Bohr Effect. Biochemistry 2017; 56:1261-1273. [PMID: 28199095 DOI: 10.1021/acs.biochem.6b01118] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Regulation of the oxygen affinity of human adult hemoglobin (Hb A) at high pH, known as the alkaline Bohr effect, is essential for its physiological function. In this study, structural mechanisms of the alkaline Bohr effect and pH-dependent O2 affinity changes were investigated via 1H nuclear magnetic resonance and visible and UV resonance Raman spectra of mutant Hbs, Hb M Iwate (αH87Y) and Hb M Boston (αH58Y). It was found that even though the binding of O2 to the α subunits is forbidden in the mutant Hbs, the O2 affinity was higher at alkaline pH than at neutral pH, and concomitantly, the Fe-His stretching frequency of the β subunits was shifted to higher values. Thus, it was confirmed for the β subunits that the stronger the Fe-His bond, the higher the O2 affinity. It was found in this study that the quaternary structure of α(Fe3+)β(Fe2+-CO) of the mutant Hb is closer to T than to the ordinary R at neutral pH. The retained Aspβ94-Hisβ146 hydrogen bond makes the extent of proton release smaller upon ligand binding from Hisβ146, known as one of residues contributing to the alkaline Bohr effect. For these T structures, the Aspα94-Trpβ37 hydrogen bond in the hinge region and the Tyrα42-Aspβ99 hydrogen bond in the switch region of the α1-β2 interface are maintained but elongated at alkaline pH. Thus, a decrease in tension in the Fe-His bond of the β subunits at alkaline pH causes a substantial increase in the change in global structure upon binding of CO to the β subunit.
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Affiliation(s)
- Shigenori Nagatomo
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba , Tsukuba, Ibaraki 305-8571, Japan
| | - Miki Okumura
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba , Tsukuba, Ibaraki 305-8571, Japan
| | - Kazuya Saito
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba , Tsukuba, Ibaraki 305-8571, Japan
| | - Takashi Ogura
- Picobiology Institute, Graduate School of Life Science, University of Hyogo , 3-2-1 Kouto, Kamigori, Ako-gun, Hyogo 678-1297, Japan
| | - Teizo Kitagawa
- Picobiology Institute, Graduate School of Life Science, University of Hyogo , 3-2-1 Kouto, Kamigori, Ako-gun, Hyogo 678-1297, Japan
| | - Masako Nagai
- Research Center for Micro-Nano Technology, Hosei University , Koganei, Tokyo 184-0003, Japan.,School of Health Sciences, College of Medical, Pharmaceutical and Health Sciences, Kanazawa University , Kanazawa, Ishikawa 920-0942, Japan
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4
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Metal ion coordination in ‘R’ and ‘T’ state hybrid hemoglobins as revealed by optical, EPR and sulphhydryl reactivity studies. J CHEM SCI 2016. [DOI: 10.1007/bf03356101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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5
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Doctor A, Stamler JS. Nitric oxide transport in blood: a third gas in the respiratory cycle. Compr Physiol 2013; 1:541-68. [PMID: 23737185 DOI: 10.1002/cphy.c090009] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The trapping, processing, and delivery of nitric oxide (NO) bioactivity by red blood cells (RBCs) have emerged as a conserved mechanism through which regional blood flow is linked to biochemical cues of perfusion sufficiency. We present here an expanded paradigm for the human respiratory cycle based on the coordinated transport of three gases: NO, O₂, and CO₂. By linking O₂ and NO flux, RBCs couple vessel caliber (and thus blood flow) to O₂ availability in the lung and to O₂ need in the periphery. The elements required for regulated O₂-based signal transduction via controlled NO processing within RBCs are presented herein, including S-nitrosothiol (SNO) synthesis by hemoglobin and O₂-regulated delivery of NO bioactivity (capture, activation, and delivery of NO groups at sites remote from NO synthesis by NO synthase). The role of NO transport in the respiratory cycle at molecular, microcirculatory, and system levels is reviewed. We elucidate the mechanism through which regulated NO transport in blood supports O₂ homeostasis, not only through adaptive regulation of regional systemic blood flow but also by optimizing ventilation-perfusion matching in the lung. Furthermore, we discuss the role of NO transport in the central control of breathing and in baroreceptor control of blood pressure, which subserve O₂ supply to tissue. Additionally, malfunctions of this transport and signaling system that are implicated in a wide array of human pathophysiologies are described. Understanding the (dys)function of NO processing in blood is a prerequisite for the development of novel therapies that target the vasoactive capacities of RBCs.
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Affiliation(s)
- Allan Doctor
- Washington University School of Medicine, Department of Pediatrics, St. Louis, MO, USA
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6
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Yi J, Thomas LM, Musayev FN, Safo MK, Richter-Addo GB. Crystallographic trapping of heme loss intermediates during the nitrite-induced degradation of human hemoglobin. Biochemistry 2011; 50:8323-32. [PMID: 21863786 DOI: 10.1021/bi2009322] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Heme is an important cofactor in a large number of essential proteins and is often involved in small molecule binding and activation. Loss of heme from proteins thus negatively affects the function of these proteins but is also an important component of iron recycling. The characterization of intermediates that form during the loss of heme from proteins has been problematic, in a large part, because of the instability of such intermediates. We have characterized, by X-ray crystallography, three compounds that form during the nitrite-induced degradation of human α(2)β(2) hemoglobin (Hb). The first is an unprecedented complex that exhibits a large β heme displacement of 4.8 Å toward the protein exterior; the heme displacement is stabilized by the binding of the distal His residue to the heme Fe, which in turn allows for the unusual binding of an exogenous ligand on the proximal face of the heme. We have also structurally characterized complexes that display regiospecific nitration of the heme at the 2-vinyl position; we show that heme nitration is not a prerequisite for heme loss. Our results provide structural insight into a possible pathway for nitrite-induced loss of heme from human Hb.
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Affiliation(s)
- Jun Yi
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, United States.
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7
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Savino C, Miele AE, Draghi F, Johnson KA, Sciara G, Brunori M, Vallone B. Pattern of cavities in globins: The case of human hemoglobin. Biopolymers 2009; 91:1097-107. [DOI: 10.1002/bip.21201] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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8
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Balakrishnan G, Ibrahim M, Mak PJ, Hata J, Kincaid JR, Spiro TG. Linking conformation change to hemoglobin activation via chain-selective time-resolved resonance Raman spectroscopy of protoheme/mesoheme hybrids. J Biol Inorg Chem 2009; 14:741-50. [PMID: 19288145 PMCID: PMC2880192 DOI: 10.1007/s00775-009-0487-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2008] [Accepted: 02/19/2009] [Indexed: 11/28/2022]
Abstract
Time-resolved resonance Raman (RR) spectra are reported for hemoglobin (Hb) tetramers, in which the alpha and beta chains are selectively substituted with mesoheme. The Soret absorption band shift in mesoheme relative to protoheme permits chain-selective recording of heme RR spectra. The evolution of these spectra following HbCO photolysis shows that the geminate recombination rates and the yields are the same for the two chains, consistent with recent results on (15)N-heme isotopomer hybrids. The spectra also reveal systematic shifts in the deoxyheme nu (4) and nu (Fe-His) RR bands, which are anticorrelated. These shifts are resolved for the successive intermediates in the protein structure, which have previously been determined from time-resolved UV RR spectra. Both chains show Fe-His bond compression in the immediate photoproduct, which relaxes during the formation of the first intermediate, R(deoxy) (0.07 micros), in which the proximal F-helix is proposed to move away from the heme. Subsequently, the Fe-His bond weakens, more so for the alpha chains than for the beta chains. The weakening is gradual for the beta chains, but is abrupt for the alpha chains, coinciding with completion of the R-T quaternary transition, at 20 micros. Since the transition from fast- to slow-rebinding Hb also occurs at 20 micros, the drop in the alpha chain nu (Fe-His) supports the localization of ligation restraint to tension in the Fe-His bond, at least in the alpha chains. The mechanism is more complex in the beta chains.
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9
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Yonetani T, Laberge M. Protein dynamics explain the allosteric behaviors of hemoglobin. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:1146-58. [PMID: 18519045 DOI: 10.1016/j.bbapap.2008.04.025] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2007] [Revised: 03/18/2008] [Accepted: 04/22/2008] [Indexed: 11/26/2022]
Abstract
Bohr, Hasselbalch, and Krogh discovered homotropic and heterotropic allosteric behaviors of hemoglobin (Hb) in 1903/1904. A chronological description since then of selected principal models of the allosteric mechanism of Hb, such as the Adair scheme, the MWC two-state concerted model, the KNF induced-fit sequential model, the Perutz stereochemical model, the tertiary two-state model, and the global allostery model (an expanded MWC models), is concisely presented, followed by analysis and discussion of their limitations and deficiencies. The determination of X-ray crystallographic structures of deoxy- and ligated-Hb and the structure-based stereochemical model by Perutz are an epoch-making event in this history. However, his assignment of low-affinity deoxy- and high-affinity oxy-quaternary structures of Hb to the T- and R-states, respectively, though apparently reasonable, and as well as his hypothesis that the T-/R-quaternary structural transition regulates the oxygen-affinity, have created confusions and side-tracked studies of Hb on the structure-function relationship. The differences in static molecular structures of Hb between T(deoxy)- and R(oxy)-quaternary states reported in detail by Perutz and others are ligation-linked structural changes, but not related to the control/regulation of the oxygen-affinity. The oxygen-affinity (K(T) and K(R)) of Hb has been shown to be regulated by the heterotropic effector-linked tertiary structural changes without involving the T/R-quaternary changes. However, a recent high-resolution crystallographic analysis of Hb with different oxygen-affinities shows that static molecular structures of Hb determined by crystallography can neither identify the nature of the T(low-affinity) functional state nor decipher the mechanism by which Hb stores free energy in the T(low-affinity) functional state. Molecular dynamics simulations show that fluctuations of helices of oxy-Hb are increased upon de-oxygenation and/or binding 2,3-biphosphoglycerate. These are known to lower the oxygen-affinity of Hb. It is proposed that the coordination mode of the heme Fe with proximal and distal His is modulated by these helical fluctuations, resulting in the modulation of the oxygen-affinity of Hb. Therefore, it is proposed that the oxygen-affinity of Hb is regulated by pentanary (the 5th-order time-dependent or dynamic) tertiary structural changes rather than the T-/R-quaternary structural transitions in Hb. Homotropic and heterotropic allosteric effects of Hb are oxygen- and effector-linked, conformational entropy-driven entropy-enthalpy compensation phenomena and not much to do with static structural changes. The dynamic allostery model, which integrates these observations, provides the structural basis for the global allostery model (an expanded MWC model).
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Affiliation(s)
- Takashi Yonetani
- Department of Biochemistry and Biophysics and the Johnson Research Foundation, University of Pennsylvania, Philadelphia, Pennsylvania 19194-6059, USA.
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10
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Maréchal JD, Maseras F, Lledós A, Mouawad L, Perahia D. A DFT study on the relative affinity for oxygen of the alpha and beta subunits of hemoglobin. J Comput Chem 2007; 27:1446-53. [PMID: 16807972 DOI: 10.1002/jcc.20427] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
DFT calculations are carried out on computational models of the active center of the alpha and beta subunits of hemoglobin in both its oxygenated (R) and deoxygenated (T) states. The computational models are defined by the full heme group, including all porphyrin substituents, and the four amino acids closer to it. The role of the protein environment is introduced by freezing the position of the alpha carbon atom of each of the four amino acids to the positions they have in the available PDB structures. Oxygen affinity is then evaluated by computing the energy difference between the optimized structures of the oxygenated and deoxygenated forms of each model. The results indicate a higher affinity of the alpha subunits over the beta ones. Analysis of the computed structures points out to the strength of the hydrogen bond between the distal histidine and the oxygen molecule as a key factor in discriminating the different systems.
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Affiliation(s)
- Jean-Didier Maréchal
- Institut de Biochimie et de Biophysique Moléculaire et Cellulaire, Université Paris-Sud, Bât. 430, 94105 Orsay Cedex, France
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11
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12
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Samuni U, Roche CJ, Dantsker D, Juszczak LJ, Friedman JM. Modulation of reactivity and conformation within the T-quaternary state of human hemoglobin: the combined use of mutagenesis and sol-gel encapsulation. Biochemistry 2006; 45:2820-35. [PMID: 16503637 PMCID: PMC3558951 DOI: 10.1021/bi050010i] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A range of conformationally distinct functional states within the T quaternary state of hemoglobin are accessed and probed using a combination of mutagenesis and sol-gel encapsulation that greatly slow or eliminate the T --> R transition. Visible and UV resonance Raman spectroscopy are used to probe the proximal strain at the heme and the status of the alpha(1)beta(2) interface, respectively, whereas CO geminate and bimolecular recombination traces in conjunction with MEM (maximum entropy method) analysis of kinetic populations are used to identify functionally distinct T-state populations. The mutants used in this study are Hb(Nbeta102A) and the alpha99-alpha99 cross-linked derivative of Hb(Wbeta37E). The former mutant, which binds oxygen noncooperatively with very low affinity, is used to access low-affinity ligated T-state conformations, whereas the latter mutant is used to access the high-affinity end of the distribution of T-state conformations. A pattern emerges within the T state in which ligand reactivity increases as both the proximal strain and the alpha(1)beta(2) interface interactions are progressively lessened after ligand binding to the deoxy T-state species. The ligation and effector-dependent interplay between the heme environment and the stability of the Trp beta37 cluster in the hinge region of the alpha(1)beta(2) interface appears to determine the distribution of the ligated T-state species generated upon ligand binding. A qualitative model is presented, suggesting that different T quaternary structures modulate the stability of different alphabeta dimer conformations within the tetramer.
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13
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Doctor A, Platt R, Sheram ML, Eischeid A, McMahon T, Maxey T, Doherty J, Axelrod M, Kline J, Gurka M, Gow A, Gaston B. Hemoglobin conformation couples erythrocyte S-nitrosothiol content to O2 gradients. Proc Natl Acad Sci U S A 2005; 102:5709-14. [PMID: 15824313 PMCID: PMC556285 DOI: 10.1073/pnas.0407490102] [Citation(s) in RCA: 166] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
It is proposed that the bond between nitric oxide (NO) and the Hb thiol Cys-beta(93) (SNOHb) is favored when hemoglobin (Hb) is in the relaxed (R, oxygenated) conformation, and that deoxygenation to tense (T) state destabilizes the SNOHb bond, allowing transfer of NO from Hb to form other (vasoactive) S-nitrosothiols (SNOs). However, it has not previously been possible to measure SNOHb without extensive Hb preparation, altering its allostery and SNO distribution. Here, we have validated an assay for SNOHb that uses carbon monoxide (CO) and cuprous chloride (CuCl)-saturated Cys. This assay is specific for SNOs and sensitive to 2-5 pmol. Uniquely, it measures the total SNO content of unmodified erythrocytes (RBCs) (SNO(RBC)), preserving Hb allostery. In room air, the ratio of SNO(RBC) to Hb in intact RBCs is stable over time, but there is a logarithmic loss of SNO(RBC) with oxyHb desaturation (slope, 0.043). This decay is accelerated by extraerythrocytic thiol (slope, 0.089; P < 0.001). SNO(RBC) stability is uncoupled from O(2) tension when Hb is locked in the R state by CO pretreatment. Also, SNO(RBC) is increased approximately 20-fold in human septic shock (P = 0.002) and the O(2)-dependent vasoactivity of RBCs is affected profoundly by SNO content in a murine lung bioassay. These data demonstrate that SNO content and O(2) saturation are tightly coupled in intact RBCs and that this coupling is likely to be of pathophysiological significance.
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Affiliation(s)
- Allan Doctor
- Department of Pediatric Critical Care, University of Virginia, Charlottesville, VA 22908, USA
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14
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Adachi SI, Park SY, Tame JRH, Shiro Y, Shibayama N. Direct observation of photolysis-induced tertiary structural changes in hemoglobin. Proc Natl Acad Sci U S A 2003; 100:7039-44. [PMID: 12773618 PMCID: PMC165826 DOI: 10.1073/pnas.1230629100] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2003] [Indexed: 11/18/2022] Open
Abstract
Human Hb, an alpha2beta2 tetrameric oxygen transport protein that switches from a T (tense) to an R (relaxed) quaternary structure during oxygenation, has long served as a model for studying protein allostery in general. Time-resolved spectroscopic measurements after photodissociation of CO-liganded Hb have played a central role in exploring both protein dynamical responses and molecular cooperativity, but the direct visualization and the structural consequences of photodeligation have not yet been reported. Here we present an x-ray study of structural changes induced by photodissociation of half-liganded T-state and fully liganded R-state human Hb at cryogenic temperatures (25-35 K). On photodissociation of CO, structural changes involving the heme and the F-helix are more marked in the alpha subunit than in the beta subunit, and more subtle in the R state than in the T state. Photodeligation causes a significant sliding motion of the T-state beta heme. Our results establish that the structural basis of the low affinity of the T state is radically different between the subunits, because of differences in the packing and chemical tension at the hemes.
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Affiliation(s)
- Shin-Ichi Adachi
- RIKEN Harima Institute/SPring-8, 1-1-1 Kouto, Mikazuki, Sayo, Hyogo 679-5148, Japan.
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15
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Mouawad L, Perahia D, Robert CH, Guilbert C. New insights into the allosteric mechanism of human hemoglobin from molecular dynamics simulations. Biophys J 2002; 82:3224-45. [PMID: 12023247 PMCID: PMC1302112 DOI: 10.1016/s0006-3495(02)75665-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
It is still difficult to obtain a precise structural description of the transition between the deoxy T-state and oxy R-state conformations of human hemoglobin, despite a large number of experimental studies. We used molecular dynamics with the Path Exploration with Distance Constraints (PEDC) method to provide new insights into the allosteric mechanism at the atomic level, by simulating the T-to-R transition. The T-state molecule in the absence of ligands was seen to have a natural propensity for dimer rotation, which nevertheless would be hampered by steric hindrance in the "joint" region. The binding of a ligand to the alpha subunit would prevent such hindrance due to the coupling between this region and the alpha proximal histidine, and thus facilitate completion of the dimer rotation. Near the end of this quaternary transition, the "switch" region adopts the R conformation, resulting in a shift of the beta proximal histidine. This leads to a sliding of the beta-heme, the effect of which is to open the beta-heme's distal side, increasing the accessibility of the Fe atom and thereby the affinity of the protein. Our simulations are globally consistent with the Perutz strereochemical mechanism.
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Affiliation(s)
- Liliane Mouawad
- Laboratoire de Modélisation et Ingénierie des Protéines, Institut de Biochimie et de Biophysique Moléculaire et Cellulaire, CNRS, Unité Mixte de Recherche 8619, Université Paris-Sud, 91405 Orsay cedex, France.
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16
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Venkatesh B, Hori H, Miyazaki G, Nagatomo S, Kitagawa T, Morimoto H. Coordination geometry of Cu-porphyrin in Cu(II)-Fe(II) hybrid hemoglobins studied by Q-band EPR and resonance Raman spectroscopies. J Inorg Biochem 2002; 88:310-5. [PMID: 11897345 DOI: 10.1016/s0162-0134(01)00391-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Cu(II)-Fe(II) hybrid hemoglobins were investigated by UV-vis, Q-band (35 GHz) EPR and resonance Raman spectroscopies. EPR results indicated that Cu-porphyrin in alpha-subunit within hybrid hemoglobin had either 5- or 4-coordination geometry depending on the pH conditions, while Cu-porphyrin in beta-subunit had only 5-coordination geometry at high and low pH values. These results were consistent with UV-vis absorption results. A new resonance Raman band appeared around 190 cm(-1), which was present whenever 5-coordinated Cu-porphyrin existed in Cu(II)-Fe(II) hybrid hemoglobins irrespective of the coordination number in Fe(II) subunit. This Raman band might be assigned to Cu-N(epsilon) (His) stretching mode. These results are direct demonstration of the existence of coordination changes of Cu-porphyrin in alpha-subunit within hybrid hemoglobin by shifting the molecular conformation from fully unliganded state to intermediately liganded state.
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Affiliation(s)
- Balan Venkatesh
- Division of Biophysical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
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17
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Barrick D, Ho NT, Simplaceanu V, Ho C. Distal ligand reactivity and quaternary structure studies of proximally detached hemoglobins. Biochemistry 2001; 40:3780-95. [PMID: 11300758 DOI: 10.1021/bi002165q] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The linkage between the proximal histidines and the proximal polypeptide in normal adult human hemoglobin (Hb A) has been proposed to play a major role in transmitting allosteric effects between oxygen binding sites [Perutz, M. F. (1970) Nature 228, 726-734]. Here we present circular dichroism (CD), (1)H NMR, analytical ultracentrifugation, and stopped-flow kinetic data to better define the quaternary structure of hemoglobins in which the linkage between the proximal histidines and the polypeptide backbone has been broken [Barrick et al. Nat. Struct. Biol. 4, 78-83 (1997)] and to characterize the distal ligand binding properties of these proximally detached Hbs. CD spectroscopy indicates that rHb (alphaH87G) and rHb (alphaH87G/betaH92G) retain at least partial T-quaternary structure with distal ligand bound, whereas rHb (betaH92G) does not, consistent with (1)H NMR spectra. Analytical ultracentrifugation reveals significant tetramer dissociation in rHb (betaH92G) to be the likely cause of loss of T-state markers. These quaternary structure studies indicate that in distally liganded Hb, the T-state is compatible with proximal linkages in the beta- but not the alpha-chains. (1)H NMR titrations of rHb (alphaH87G) with n-butyl isocyanide demonstrate the alpha-chains to be of high affinity as compared with the beta-chains. Comparing ligand association and dissociation rates between the rHb (alphaH87G) variant with the T- and R-states of wild-type Hb A indicates that at the alpha-chains, carbon monoxide affinity is modulated entirely by the proximal linkage, rather than from distal interactions. Some residual allosteric interactions may remain operative at the beta-chains of rHb (alphaH87G).
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Affiliation(s)
- D Barrick
- T. C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore Maryland 21218, USA
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18
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Miyazaki G, Morimoto H, Yun KM, Park SY, Nakagawa A, Minagawa H, Shibayama N. Magnesium(II) and zinc(II)-protoporphyrin IX's stabilize the lowest oxygen affinity state of human hemoglobin even more strongly than deoxyheme. J Mol Biol 1999; 292:1121-36. [PMID: 10512707 DOI: 10.1006/jmbi.1999.3124] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Studies of oxygen equilibrium properties of Mg(II)-Fe(II) and Zn(II)-Fe(II) hybrid hemoglobins (i.e. alpha2(Fe)beta2(M) and alpha2(M)beta2(Fe); M=Mg(II), Zn(II) (neither of these closed-shell metal ions binds oxygen or carbon monoxide)) are reported along with the X-ray crystal structures of alpha2(Fe)beta2(Mg) with and without CO bound. We found that Mg(II)-Fe(II) hybrids resemble Zn(II)-Fe(II) hybrids very closely in oxygen equilibrium properties. The Fe(II)-subunits in these hybrids bind oxygen with very low affinities, and the effect of allosteric effectors, such as proton and/or inositol hexaphosphate, is relatively small. We also found a striking similarity in spectrophotometric properties between Mg(II)-Fe(II) and Zn(II)-Fe(II) hybrids, particularly, the large spectral changes that occur specifically in the metal-containing beta subunits upon the R-T transition of the hybrids. In crystals, both alpha2(Fe)beta2(Mg) and alpha2(Fe-CO)beta2(Mg) adopt the quaternary structure of deoxyhemoglobin. These results, combined with the re-evaluation of the oxygen equilibrium properties of normal hemoglobin, low-affinity mutants, and metal substituted hybrids, point to a general tendency of human hemoglobin that when the association equilibrium constant of hemoglobin for the first binding oxygen molecule (K1) approaches 0.004 mmHg(-1), the cooperativity as well as the effect of allosteric effectors is virtually abolished. This is indicative of the existence of a distinct thermodynamic state which determines the lowest oxygen affinity of human hemoglobin. Moreover, excellent agreement between the reported oxygen affinity of deoxyhemoglobin in crystals and the lowest affinity in solution leads us to propose that the classical T structure of deoxyhemoglobin in the crystals represents the lowest affinity state in solution. We also survey the oxygen equilibrium properties of various metal-substituted hybrid hemoglobins studied over the past 20 years in our laboratory. The bulk of these data are consistent with the Perutz's trigger mechanism, in that the affinity of a metal hybrid is determined by the ionic radius of the metal, and also by the steric effect of the distal ligand, if present. However, there remains a fundamental contradiction among the oxygen equilibrium properties of the beta substituted hybrid hemoglobins.
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Affiliation(s)
- G Miyazaki
- Division of Biophysical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan.
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19
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Kosaka H. Nitric oxide and hemoglobin interactions in the vasculature. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1411:370-7. [PMID: 10320669 DOI: 10.1016/s0005-2728(99)00026-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
As an endothelium-derived relaxing factor, nitric oxide (NO) maintains blood flow and O2 transport to tissues. Under normal conditions a delicate balance exists in the vascular system between endothelium-derived NO, an antioxidant, and the pro-oxidant elements of the vascular system, O-2, and peroxynitrite (a by-product of the reaction of NO and superoxide); in addition there is a balance between neurogenic tonic contraction and NO-mediated relaxation. The former balance can be disrupted in favor of peroxynitrite and hydrogen peroxide under the conditions of ischemia/reperfusion. This review suggests that NO may be beneficial, not only in terms of its new potential in improving O2 transport without accompanying significant increase in tissue blood flow, but also in its ability to suppress the prooxidative reagents of the vascular systems. These include NO-mediated inhibition of transendothelial migration by leukocyte and the antioxidative effects of NO with regard to ischemia/reperfusion; the relevance of these hypotheses to systemic administration of NO donors is discussed.
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Affiliation(s)
- H Kosaka
- Second Department of Physiology, Kagawa Medical University, 1750-1, Ikenobe, Miki, Kita, Kagawa 761-0793, Japan.
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20
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Unzai S, Eich R, Shibayama N, Olson JS, Morimoto H. Rate constants for O2 and CO binding to the alpha and beta subunits within the R and T states of human hemoglobin. J Biol Chem 1998; 273:23150-9. [PMID: 9722544 DOI: 10.1074/jbc.273.36.23150] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Despite a large amount of work over the past 30 years, there is still no universal agreement on the differential reactivities of the individual alpha and beta subunits in human hemoglobin. To address this question systematically, we prepared a series of hybrid hemoglobins in which heme was replaced by chromium(III), manganese(III), nickel(II), and magnesium(II) protoporphyrin IXs in either the alpha or beta subunits to produce alpha2(M)beta2(Fe)1 and alpha2(Fe)beta2(M) tetramers. None of the abnormal metal complexes react with dioxygen or carbon monoxide. The O2 affinities of the resultant hemoglobins vary from 3 microM-1 (Cr(III)/Fe(II) hybrids) to 0.003 microM-1 (Mg(II)/Fe(II) hybrids), covering the full range expected for the various high (R) and low (T) affinity quaternary conformations, respectively, of human hemoglobin A0. The alpha and beta subunits in hemoglobin have similar O2 affinities in both quaternary states, despite the fact that the R to T transition causes significantly different structural changes in the alpha and beta heme pockets. This functional equivalence almost certainly evolved to maintain high n values for efficient O2 transport.
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Affiliation(s)
- S Unzai
- Department of Biophysical Engineering, Faculty of Engineering Science, Osaka University, Toyonaka, Osaka 560, Japan
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Yonetani T, Tsuneshige A, Zhou Y, Chen X. Electron paramagnetic resonance and oxygen binding studies of alpha-Nitrosyl hemoglobin. A novel oxygen carrier having no-assisted allosteric functions. J Biol Chem 1998; 273:20323-33. [PMID: 9685383 DOI: 10.1074/jbc.273.32.20323] [Citation(s) in RCA: 123] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
alpha-Nitrosyl hemoglobin, alpha(Fe-NO)2beta(Fe)2, which is frequently observed upon reaction of deoxy hemoglobin with limited quantities of NO in vitro as well as in vivo, has been synthetically prepared, and its reaction with O2 has been investigation by EPR and thermodynamic equilibrium measurements. alpha-Nitrosyl hemoglobin is relatively stable under aerobic conditions and undergoes reversible O2 binding at the heme sites of its beta-subunits. Its O2 binding is coupled to the structural/functional transition between T- (low affinity extreme) and R- (high affinity) states. This transition is linked to the reversible cleavage of the heme Fe-proximal His bonds in the alpha(Fe-NO) subunits and is sensitive to allosteric effectors, such as protons, 2,3-biphosphoglycerate, and inositol hexaphosphate. In fact, alpha(Fe-NO)2beta(Fe)2 is exceptionally sensitive to protons, as it exhibits a highly enhanced Bohr effect. The total Bohr effect of alpha-nitrosyl hemoglobin is comparable to that of normal hemoglobin, despite the fact that the oxygenation process involves only two ligation steps. All of these structural and functional evidences have been further confirmed by examining the reactivity of the sulfhydryl group of the Cysbeta93 toward 4, 4'-dipyridyl disulfide of several alpha-nitrosyl hemoglobin derivatives over a wide pH range, as a probe for quaternary structure. Despite the halved O2-carrying capacity, alpha-nitrosyl hemoglobin is fully functional (cooperative and allosterically sensitive) and could represent a versatile low affinity O2 carrier with improved features that could deliver O2 to tissues effectively even after NO is sequestered at the heme sites of the alpha-subunits. It is concluded that the NO bound to the heme sites of the alpha-subunits of hemoglobin acts as a negative allosteric effector of Hb and thus might play a role in O2/CO2 transport in the blood under physiological conditions.
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Affiliation(s)
- T Yonetani
- Department of Biochemistry and Biophysics, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19194-6089, USA.
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Kosaka H, Seiyama A. Elevation of oxygen release by nitroglycerin without an increase in blood flow in the hepatic microcirculation. Nat Med 1997; 3:456-9. [PMID: 9095182 DOI: 10.1038/nm0497-456] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The effect of nitroglycerin on oxygen (O2) release in the microcirculation was investigated by examining single, unbranched hepatic sinusoids of rats using dual-spot microspectroscopy. Nitroglycerin significantly increased O2 release from erythrocytes flowing in the sinusoids. Differences in O2 saturation of hemoglobin per unit length of the sinusoid were significantly enhanced, while there were no significant changes in erythrocyte velocity, hemoglobin concentration or oxyhemoglobin flow into the sinusoids, or in regional hepatic blood flow measured with a laser tissue blood flow meter. No change was noted for hepatic O2 consumption measured in isolated liver perfused with hemoglobin-free oxygenated buffer. Isosorbide dinitrate showed a similar but slower effect. These findings suggest that nitroglycerin and isosorbide dinitrate enhance O2 release from erythrocytes without significantly increasing tissue blood flow.
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Affiliation(s)
- H Kosaka
- First Department of Physiology, Medical School, Osaka University, Japan
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Wajcman H, Kister J, Galactéros F, Spielvogel A, Lin MJ, Vidugiris GJ, Hirsch RE, Friedman JM, Nagel RL. Hb Montefiore (126(H9)Asp-->Tyr). High oxygen affinity and loss of cooperativity secondary to C-terminal disruption. J Biol Chem 1996; 271:22990-8. [PMID: 8798486 DOI: 10.1074/jbc.271.38.22990] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Hb Montefiore was found, in the heterozygous state, in a Puerto Rican female who had a slightly elevated total Hb level. Structural analysis revealed that Asp-alpha126 was replaced by Tyr. Hb Montefiore migrates close to HbF (at pH 8.6) and accounts for 20.3% of the hemolysate. Oxygen binding of red blood cells revealed a 40% decrease in the P50 (pH 7.4) and a low n value of 1.6 (normal: 2.6). Depletion of red blood cell 2,3-DPG did not change the results. Stripped Hb Montefiore at pH 7.2 showed an 8-fold reduction in P50 (0.6 versus 4.6 mm Hg) and very low cooperativity (n = 1.2 versus 2.9 for the control). Heterotopic effectors, as 2,3-diphosphoglycerate and inositol hexaphosphate had a normal effect and in addition, they increased cooperativity. The chloride ion effect and the Bohr effect were moderately reduced. A bezafibrate derivative (L345), known to bind alpha126, increases the P50 of HbA by 9-fold, but only by 1. 5-fold that of Hb Montefiore. Combining these functional studies with intrinsic fluorescence and Resonance Raman spectroscopy, we interpret the very low n value and the high oxygen affinity for Hb Montefiore as a result of both a destabilized T state that switches to R upon ligand binding and a deoxy T state that binds ligands with higher affinity than that of deoxy HbA. Hb Montefiore still binds ligands cooperatively, but the difference in ligand binding properties of the two quaternary states has been drastically reduced.
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Affiliation(s)
- H Wajcman
- INSERM U91, Hôpital Henri Mondor, 94010 Creteil, France
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Unzai S, Hori H, Miyazaki G, Shibayama N, Morimoto H. Oxygen equilibrium properties of chromium (III)-iron (II) hybrid hemoglobins. J Biol Chem 1996; 271:12451-6. [PMID: 8647851 DOI: 10.1074/jbc.271.21.12451] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Cr(III)-Fe(II) hybrid hemoglobins, alpha 2(Cr) beta 2(Fe) and alpha 2(Fe) beta 2(Cr), in which hemes in either the alpha- or beta-subunits were substituted with chromium(III) protoporphyrin IX (Cr(III)(PPIX), were prepared and characterized by oxygen equilibrium measurements. Because Cr(III)PPIX binds neither oxygen molecules nor carbon monoxide, the oxygen equilibrium properties of Fe(II) subunits within these hybrids can be analyzed by a two-step oxygen equilibrium scheme. The oxygen equilibrium constants for both hybrids at the second oxygenation step agree with those for human adult hemoglobin at the last oxygenation step (at pH 6.5-8.4 with an without inositol hexaphosphate at 25 degrees C). The similarity between the effects of the Cr(III)PPIX and each subunits' oxygeme on the oxygen equilibrium properties of the counterpart Fe(II) subunits within hemoglobin indicate the utility of Cr(III)PPIX as a model for a permanently oxygenated heme within the hemoglobin molecule. We found that Cr(III)-Fe(II) hybrid hemoglobins have several advantages over cyanomet valency hybrid hemoglobins, which have been frequently used as a model system for partially oxygenated hemoglobins. In contrast to cyanomet heme, Cr(III)PPIX within hemoglobin is not subject to reduction with dithionite or enzymatic reduction systems. Therefore, we could obtain more accurate and reasonable oxygen equilibrium curves of Cr(III)-Fe(II) hybrids in the presence of an enzymatic reduction system, and we could obtain single crystals of deoxy-alpha 2(Cr) beta 2(Fe) when grown in low salt solution in the presence of polyethylene glycol 1000 and 50 mM dithionite.
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Affiliation(s)
- S Unzai
- Department of Biophysical Engineering, Faculty of Engineering Science, Osaka University, Japan
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Dumoulin A, Kiger L, Jiang R, Baudin V, Vasseur C, Sligar SG, Marden MC, Pagnier J, Poyart C. Loss of allosteric behaviour in recombinant hemoglobin alpha 2 beta 2(92)(F8) His-->Ala: restoration upon addition of strong effectors. FEBS Lett 1995; 374:39-42. [PMID: 7589508 DOI: 10.1016/0014-5793(95)01069-q] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In the stereochemical model proposed by Perutz [1], the Fe-His(F8) bond plays a significant role in the allosteric transition in hemoglobin and the resulting cooperativity in ligand binding. When this bond is ruptured, there is a loss in the transmission of the information concerning ligand binding; examples are Hb(NO)4 in the presence of inositol hexakisphosphate (IHP), or nickel substituted Hb hybrids which, despite being liganded, exhibit deoxy-like properties. To study the effects of the loss of the iron proximal histidine bond, we have engineered the alpha 2 beta 2(F8)H92A recombinant Hb. The replacement of the highly conserved proximal histidine F8 residue by an alanine results in a low affinity for the heme group and a loss of the allosteric properties; kinetics of CO recombination after photodissociation show only the rapid bimolecular phase, characteristic of the high affinity R-state. However, a significant amount of deoxy (T-state) kinetics are observed after addition of external effectors such as IHP. The iron-histidine bond is apparently crucial for the heme-heme interaction, but the allosteric equilibrium may still be influenced by external constraints.
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Affiliation(s)
- A Dumoulin
- Institut National de la Santé et de la Recherche Médicale U 299, Hôpital de Bicêtre, France
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Shibayama N, Ikeda-Saito M, Hori H, Itaroku K, Morimoto H, Saigo S. Oxygen equilibrium and electron paramagnetic resonance studies on copper(II)-iron(II) hybrid hemoglobins at room temperature. FEBS Lett 1995; 372:126-30. [PMID: 7556632 DOI: 10.1016/0014-5793(95)00965-c] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Copper(II)-iron(II) hybrid hemoglobins, in which hemes in either the alpha or beta subunits are substituted with copper(II) protoporphyrin IX, have been prepared. The affinities of the ferrous-subunits in both hybrids for the first binding oxygen are as low as the affinity of deoxyhemoglobin under various solution conditions, indicating the equality of behavior in copper(II) protoporphyrin IX and deoxyheme. Electron paramagnetic resonance (EPR) examinations on these hybrids at room temperature show that the interaction between copper(II) and the proximal histidine (F8) is specifically weakened in the alpha subunits within a low affinity conformation of hemoglobin. These results suggest that copper(II) protoporphyrin IX is a useful EPR probe at room temperature for investigating the deoxyheme environment in hemoglobin.
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Affiliation(s)
- N Shibayama
- Department of Physics, Jichi Medical School, Tochigi, Japan
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Sudhakar K, Loe S, Yonetani T, Vanderkooi J. Fluorescent derivatives of human hemoglobin. Differences in interaction of the porphyrin with the protein between the alpha and beta subunits. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)31624-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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28
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Tsuneshige A, Zhou Y, Yonetani T. Oxygen equilibrium studies of cross-linked iron-cobalt hybrid hemoglobins. Models for partially ligated intermediates of cobalt hemoglobin. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)49421-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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