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Yamada T, Komatsu T. Protein-Porphyrin Complex Photosensitizers for Anticancer and Antimicrobial Photodynamic Therapies. ChemMedChem 2023; 18:e202300373. [PMID: 37821798 DOI: 10.1002/cmdc.202300373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 10/09/2023] [Accepted: 10/11/2023] [Indexed: 10/13/2023]
Abstract
Photodynamic therapy (PDT) efficiently induces apoptosis through visible-light irradiation of photosensitizers (PSs) within tumors and microbial cells. Porphyrin analogues serve as widely utilized photosensitizing agents with their therapeutic abilities being governed by molecular structures and central metal ions. However, these macrocyclic compounds tend to agglutinate and form stacks in aqueous environments, resulting in a loss of photochemical activity. To overcome this limitation, encapsulation within liposomes and polymer micelles enables the dispersion of porphyrins as monomolecular entities in aqueous solutions, preventing undesirable deactivation. Recently, the use of reconstituted hemoproteins containing various metal-porphyrins and protein cages incorporating porphyrins has garnered significant interest as a new generation of biocompatible PSs. In this concept paper, we provide a comprehensive review of recent developments and trends of protein-porphyrin complex PSs for applications in anticancer and antimicrobial PDTs.
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Affiliation(s)
- Taiga Yamada
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo, 112-8551, Japan
| | - Teruyuki Komatsu
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo, 112-8551, Japan
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2
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Eaton WA. A retrospective on statistical mechanical models for hemoglobin allostery. J Chem Phys 2022; 157:184104. [PMID: 36379793 PMCID: PMC9830738 DOI: 10.1063/5.0127585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Understanding allosteric interactions in proteins has become one of the major research areas in protein science. The original aim of the famous theoretical model of Monod, Wyman, and Changeux (MWC) was to explain the regulation of enzymatic activity in biochemical pathways. However, its first successful quantitative application was to explain cooperative oxygen binding by hemoglobin, often called the "hydrogen molecule of biology." The combination of its original application and the enormous amount of research on hemoglobin has made it the paradigm for studies of allostery, especially for multi-subunit proteins, and for the development of statistical mechanical models to describe how structure determines function. This article is a historical account of the development of statistical mechanical models for hemoglobin to explain both the cooperative binding of oxygen (called homotropic effects by MWC) and how oxygen binding is affected by ligands that bind distant from the heme oxygen binding site (called heterotropic allosteric effects by MWC). This account makes clear the many remaining challenges for describing the relationship of structure to function for hemoglobin in terms of a satisfactory statistical mechanical model.
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3
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Yuan Z, De La Cruz LK, Yang X, Wang B. Carbon Monoxide Signaling: Examining Its Engagement with Various Molecular Targets in the Context of Binding Affinity, Concentration, and Biologic Response. Pharmacol Rev 2022; 74:823-873. [PMID: 35738683 DOI: 10.1124/pharmrev.121.000564] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Carbon monoxide (CO) has been firmly established as an endogenous signaling molecule with a variety of pathophysiological and pharmacological functions, including immunomodulation, organ protection, and circadian clock regulation, among many others. In terms of its molecular mechanism(s) of action, CO is known to bind to a large number of hemoproteins with at least 25 identified targets, including hemoglobin, myoglobin, neuroglobin, cytochrome c oxidase, cytochrome P450, soluble guanylyl cyclase, myeloperoxidase, and some ion channels with dissociation constant values spanning the range of sub-nM to high μM. Although CO's binding affinity with a large number of targets has been extensively studied and firmly established, there is a pressing need to incorporate such binding information into the analysis of CO's biologic response in the context of affinity and dosage. Especially important is to understand the reservoir role of hemoglobin in CO storage, transport, distribution, and transfer. We critically review the literature and inject a sense of quantitative assessment into our analyses of the various relationships among binding affinity, CO concentration, target occupancy level, and anticipated pharmacological actions. We hope that this review presents a picture of the overall landscape of CO's engagement with various targets, stimulates additional research, and helps to move the CO field in the direction of examining individual targets in the context of all of the targets and the concentration of available CO. We believe that such work will help the further understanding of the relationship of CO concentration and its pathophysiological functions and the eventual development of CO-based therapeutics. SIGNIFICANCE STATEMENT: The further development of carbon monoxide (CO) as a therapeutic agent will significantly rely on the understanding of CO's engagement with therapeutically relevant targets of varying affinity. This review critically examines the literature by quantitatively analyzing the intricate relationships among targets, target affinity for CO, CO level, and the affinity state of carboxyhemoglobin and provide a holistic approach to examining the molecular mechanism(s) of action for CO.
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Affiliation(s)
- Zhengnan Yuan
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia
| | - Ladie Kimberly De La Cruz
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia
| | - Xiaoxiao Yang
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia
| | - Binghe Wang
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia
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4
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Nagatomo S, Nagai M, Kitagawa T. Structural origin of cooperativity in human hemoglobin: a view from different roles of α and β subunits in the α2β2 tetramer. Biophys Rev 2022; 14:483-498. [PMID: 35528033 PMCID: PMC9043147 DOI: 10.1007/s12551-022-00945-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 03/14/2022] [Indexed: 11/26/2022] Open
Abstract
This mini-review, mainly based on our resonance Raman studies on the structural origin of cooperative O2 binding in human adult hemoglobin (HbA), aims to answering why HbA is a tetramer consisting of two α and two β subunits. Here, we focus on the Fe-His bond, the sole coordination bond connecting heme to a globin. The Fe-His stretching frequencies reflect the O2 affinity and also the magnitude of strain imposed through globin by inter-subunit interactions, which is the origin of cooperativity. Cooperativity was first explained by Monod, Wyman, and Changeux, referred to as the MWC theory, but later explained by the two tertiary states (TTS) theory. Here, we related the higher-order structures of globin observed mainly by vibrational spectroscopy to the MWC theory. It became clear from the recent spectroscopic studies, X-ray crystallographic analysis, and mutagenesis experiments that the Fe-His bonds exhibit different roles between the α and β subunits. The absence of the Fe-His bond in the α subunit in some mutant and artificial Hbs inhibits T to R quaternary structural change upon O2 binding. However, its absence from the β subunit in mutant and artificial Hbs simply enhances the O2 affinity of the α subunit. Accordingly, the inter-subunit interactions between α and β subunits are nonsymmetric but substantial for HbA to perform cooperative O2 binding.
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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
| | - 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
| | - Teizo Kitagawa
- Graduate School of Life Science, Picobiology Institute, University of Hyogo, Kouto, Kamigori, Ako-gun Hyogo, 678-1297 Japan
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5
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Yang X, Lu W, Wang M, Tan C, Wang B. "CO in a pill": Towards oral delivery of carbon monoxide for therapeutic applications. J Control Release 2021; 338:593-609. [PMID: 34481027 PMCID: PMC8526413 DOI: 10.1016/j.jconrel.2021.08.059] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 08/28/2021] [Accepted: 08/30/2021] [Indexed: 02/08/2023]
Abstract
Along with the impressive achievements in understanding the endogenous signaling roles and mechanism(s) of action of carbon monoxide (CO), much research has demonstrated the potential of using CO as a therapeutic agent for treating various diseases. Because of CO's toxicity at high concentrations and the observed difference in toxicity profiles of CO depending on the route of administration, this review analyzes and presents the benefits of developing orally active CO donors. Such compounds have the potential for improved safety profiles, enhancing the chance for developing CO-based therapeutics. In this review, the difference between inhalation and oral administration in terms of toxicity, CO delivery efficiency, and the potential mechanism(s) of action is analyzed. The evolution from CO gas inhalation to oral administration is also extensively analyzed by summarizing published studies up to date. The concept of "CO in a pill" can be achieved by oral administration of novel formulations of CO gas or appropriate CO donors.
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Affiliation(s)
- Xiaoxiao Yang
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, USA
| | - Wen Lu
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, USA
| | - Minjia Wang
- Department of Pharmaceutical Sciences, University of Mississippi, MS 38677, USA
| | - Chalet Tan
- Department of Pharmaceutical Sciences, University of Mississippi, MS 38677, USA
| | - Binghe Wang
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, USA.
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6
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Olson JS. Kinetic mechanisms for O 2 binding to myoglobins and hemoglobins. Mol Aspects Med 2021; 84:101024. [PMID: 34544605 DOI: 10.1016/j.mam.2021.101024] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 09/06/2021] [Accepted: 09/12/2021] [Indexed: 11/29/2022]
Abstract
Antonini and Brunori's 1971 book "Hemoglobin and Myoglobin in Their Reactions with Ligands" was a truly remarkable publication that summarized almost 100 years of research on O2 binding to these globins. Over the ensuing 50 years, ultra-fast laser photolysis techniques, high-resolution and time resolved X-ray crystallography, molecular dynamics simulations, and libraries of recombinant myoglobin (Mb) and hemoglobin (Hb) variants have provided structural interpretations of O2 binding to these proteins. The resultant mechanisms provide quantitative descriptions of the stereochemical factors that govern overall affinity, including proximal and distal steric restrictions that affect iron reactivity and favorable positive electrostatic interactions that preferentially stabilize bound O2. The pathway for O2 uptake and release by Mb and subunits of Hb has been mapped by screening libraries of site-directed mutants in laser photolysis experiments. O2 enters mammalian Mb and the α and β subunits of human HbA through a channel created by upward and outward rotation of the distal His at the E7 helical position, is non-covalently captured in the interior of the distal cavity, and then internally forms a bond with the heme Fe(II) atom. O2 dissociation is governed by disruption of hydrogen bonding interactions with His (E7), breakage of the Fe(II)-O2 bond, and then competition between rebinding and escape through the E7-gate. The structural features that govern the rates of both the individual steps and overall reactions have been determined and provide the framework for: (1) defining the physiological functions of specific globins and their evolution; (2) understanding the clinical features of hemoglobinopathies; and (3) designing safer and more efficient acellular hemoglobin-based oxygen carriers (HBOCs) for transfusion therapy, organ preservation, and other commercially relevant O2 transport and storage processes.
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Affiliation(s)
- John S Olson
- Department of Biosciences, Rice University, Houston, TX, 77005, USA.
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7
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Ciaccio C, Coletta A, Coletta M. Role of hemoglobin structural-functional relationships in oxygen transport. Mol Aspects Med 2021; 84:101022. [PMID: 34509280 DOI: 10.1016/j.mam.2021.101022] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Revised: 09/02/2021] [Accepted: 09/03/2021] [Indexed: 10/20/2022]
Abstract
The molecular mechanism of O2 binding to hemoglobin (Hb) has been critically reviewed on the basis of the information built up in the last decades. It allows to describe in detail from the kinetic and thermodynamic viewpoint the process of O2 uptake in the lungs and release to the tissues, casting some light on the physiological and pathological aspects of this process. The relevance of structural-functional relationships for O2 binding is particularly outlined in the case of poorly vascularized tissues, such as retina, briefly discussing of strategies employed for optimization of oxygen supply to this type of tissues.
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Affiliation(s)
- Chiara Ciaccio
- Department of Clinical Sciences and Translational Medicine, University of Roma Tor Vergata, Via Montpellier 1, I-00133 Roma, Italy
| | | | - Massimo Coletta
- Department of Clinical Sciences and Translational Medicine, University of Roma Tor Vergata, Via Montpellier 1, I-00133 Roma, Italy; IRCCS Fondazione Bietti, Rome, Italy.
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8
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Lepeshkevich SV, Sazanovich IV, Parkhats MV, Gilevich SN, Dzhagarov BM. Towards understanding non-equivalence of α and β subunits within human hemoglobin in conformational relaxation and molecular oxygen rebinding. Chem Sci 2021; 12:7033-7047. [PMID: 34123331 PMCID: PMC8153241 DOI: 10.1039/d1sc00712b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Picosecond to millisecond laser time-resolved transient absorption spectroscopy was used to study molecular oxygen (O2) rebinding and conformational relaxation following O2 photodissociation in the α and β subunits within human hemoglobin in the quaternary R-like structure. Oxy-cyanomet valency hybrids, α2(Fe2+-O2)β2(Fe3+-CN) and α2(Fe3+-CN)β2(Fe2+-O2), were used as models for oxygenated R-state hemoglobin. An extended kinetic model for geminate O2 rebinding in the ferrous hemoglobin subunits, ligand migration between the primary and secondary docking site(s), and nonexponential tertiary relaxation within the R quaternary structure, was introduced and discussed. Significant functional non-equivalence of the α and β subunits in both the geminate O2 rebinding and concomitant structural relaxation was revealed. For the β subunits, the rate constant for the geminate O2 rebinding to the unrelaxed tertiary structure and the tertiary transition rate were found to be greater than the corresponding values for the α subunits. The conformational relaxation following the O2 photodissociation in the α and β subunits was found to decrease the rate constant for the geminate O2 rebinding, this effect being more than one order of magnitude greater for the β subunits than for the α subunits. Evidence was provided for the modulation of the O2 rebinding to the individual α and β subunits within human hemoglobin in the R-state structure by the intrinsic heme reactivity through a change in proximal constraints upon the relaxation of the tertiary structure on a picosecond to microsecond time scale. Our results demonstrate that, for native R-state oxyhemoglobin, O2 rebinding properties and spectral changes following the O2 photodissociation can be adequately described as the sum of those for the α and β subunits within the valency hybrids. The isolated β chains (hemoglobin H) show similar behavior to the β subunits within the valency hybrids and can be used as a model for the β subunits within the R-state oxyhemoglobin. At the same time, the isolated α chains behave differently to the α subunits within the valency hybrids.
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Affiliation(s)
- Sergei V Lepeshkevich
- B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus 68 Nezavisimosti Ave Minsk 220072 Belarus
| | - Igor V Sazanovich
- Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory Harwell Campus OX11 0QX UK
| | - Marina V Parkhats
- B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus 68 Nezavisimosti Ave Minsk 220072 Belarus
| | - Syargey N Gilevich
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus 5 Academician V. F. Kuprevich Street Minsk 220141 Belarus
| | - Boris M Dzhagarov
- B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus 68 Nezavisimosti Ave Minsk 220072 Belarus
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9
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Ascenzi P, De Simone G, Tundo GR, Coletta M. Kinetics of cyanide and carbon monoxide dissociation from ferrous human haptoglobin:hemoglobin(II) complexes. J Biol Inorg Chem 2020; 25:351-360. [DOI: 10.1007/s00775-020-01766-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 02/12/2020] [Indexed: 12/17/2022]
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10
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Ligand-dependent inequivalence of the α and β subunits of ferric human hemoglobin bound to haptoglobin. J Inorg Biochem 2020; 202:110814. [DOI: 10.1016/j.jinorgbio.2019.110814] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 08/26/2019] [Accepted: 08/31/2019] [Indexed: 12/16/2022]
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11
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Morita Y, Yamada T, Kureishi M, Kihira K, Komatsu T. Quaternary Structure Analysis of a Hemoglobin Core in Hemoglobin–Albumin Cluster. J Phys Chem B 2018; 122:12031-12039. [DOI: 10.1021/acs.jpcb.8b10077] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Yoshitsugu Morita
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
| | - Taiga Yamada
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
| | - Moeka Kureishi
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
| | - Kiyohito Kihira
- JEM Utilization Center, Human Spaceflight Technology Directorate, Japan Aerospace Exploration Agency (JAXA), 2-1-1 Sengen, Tsukuba-shi, Ibaraki 305-8505, Japan
| | - Teruyuki Komatsu
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
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12
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Gell DA. Structure and function of haemoglobins. Blood Cells Mol Dis 2017; 70:13-42. [PMID: 29126700 DOI: 10.1016/j.bcmd.2017.10.006] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2017] [Revised: 10/29/2017] [Accepted: 10/30/2017] [Indexed: 12/18/2022]
Abstract
Haemoglobin (Hb) is widely known as the iron-containing protein in blood that is essential for O2 transport in mammals. Less widely recognised is that erythrocyte Hb belongs to a large family of Hb proteins with members distributed across all three domains of life-bacteria, archaea and eukaryotes. This review, aimed chiefly at researchers new to the field, attempts a broad overview of the diversity, and common features, in Hb structure and function. Topics include structural and functional classification of Hbs; principles of O2 binding affinity and selectivity between O2/NO/CO and other small ligands; hexacoordinate (containing bis-imidazole coordinated haem) Hbs; bacterial truncated Hbs; flavohaemoglobins; enzymatic reactions of Hbs with bioactive gases, particularly NO, and protection from nitrosative stress; and, sensor Hbs. A final section sketches the evolution of work on the structural basis for allosteric O2 binding by mammalian RBC Hb, including the development of newer kinetic models. Where possible, reference to historical works is included, in order to provide context for current advances in Hb research.
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Affiliation(s)
- David A Gell
- School of Medicine, University of Tasmania, TAS 7000, Australia.
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13
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Tertiary and quaternary structural basis of oxygen affinity in human hemoglobin as revealed by multiscale simulations. Sci Rep 2017; 7:10926. [PMID: 28883619 PMCID: PMC5589765 DOI: 10.1038/s41598-017-11259-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 08/22/2017] [Indexed: 11/30/2022] Open
Abstract
Human hemoglobin (Hb) is a benchmark protein of structural biology that shaped our view of allosterism over 60 years ago, with the introduction of the MWC model based on Perutz structures of the oxy(R) and deoxy(T) states and the more recent Tertiary Two-State model that proposed the existence of individual subunit states -“r” and “t”-, whose structure is yet unknown. Cooperative oxygen binding is essential for Hb function, and despite decades of research there are still open questions related to how tertiary and quaternary changes regulate oxygen affinity. In the present work, we have determined the free energy profiles of oxygen migration and for HisE7 gate opening, with QM/MM calculations of the oxygen binding energy in order to address the influence of tertiary differences in the control of oxygen affinity. Our results show that in the α subunit the low to high affinity transition is achieved by a proximal effect that mostly affects oxygen dissociation and is the driving force of the allosteric transition, while in the β subunit the affinity change results from a complex interplay of proximal and distal effects, including an increase in the HE7 gate opening, that as shown by free energy profiles promotes oxygen uptake.
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14
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Bissé E, Schaeffer-Reiss C, Van Dorsselaer A, Alayi TD, Epting T, Winkler K, Benitez Cardenas AS, Soman J, Birukou I, Samuel PP, Olson JS. Hemoglobin Kirklareli (α H58L), a New Variant Associated with Iron Deficiency and Increased CO Binding. J Biol Chem 2016; 292:2542-2555. [PMID: 28011635 DOI: 10.1074/jbc.m116.764274] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Revised: 12/19/2016] [Indexed: 11/06/2022] Open
Abstract
Mutations in hemoglobin can cause a wide range of phenotypic outcomes, including anemia due to protein instability and red cell lysis. Uncovering the biochemical basis for these phenotypes can provide new insights into hemoglobin structure and function as well as identify new therapeutic opportunities. We report here a new hemoglobin α chain variant in a female patient with mild anemia, whose father also carries the trait and is from the Turkish city of Kirklareli. Both the patient and her father had a His-58(E7) → Leu mutation in α1. Surprisingly, the patient's father is not anemic, but he is a smoker with high levels of HbCO (∼16%). To understand these phenotypes, we examined recombinant human Hb (rHb) Kirklareli containing the α H58L replacement. Mutant α subunits containing Leu-58(E7) autoxidize ∼8 times and lose hemin ∼200 times more rapidly than native α subunits, causing the oxygenated form of rHb Kirklareli to denature very rapidly under physiological conditions. The crystal structure of rHb Kirklareli shows that the α H58L replacement creates a completely apolar active site, which prevents electrostatic stabilization of bound O2, promotes autoxidation, and enhances hemin dissociation by inhibiting water coordination to the Fe(III) atom. At the same time, the mutant α subunit has an ∼80,000-fold higher affinity for CO than O2, causing it to rapidly take up and retain carbon monoxide, which prevents denaturation both in vitro and in vivo and explains the phenotypic differences between the father, who is a smoker, and his daughter.
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Affiliation(s)
- Emmanuel Bissé
- From the Institute for Clinical Chemistry and Laboratory Medicine, University Medical Center, Hugstetterstrasse 55, D-79106 Freiburg, Germany
| | - Christine Schaeffer-Reiss
- the BioOrganic Mass Spectrometry Laboratory (LSMBO), IPHC, Université de Strasbourg, 25 Rue Becquerel, 67087 Strasbourg, France.,the IPHC, CNRS, UMR7178, 67087 Strasbourg, France, and
| | - Alain Van Dorsselaer
- the BioOrganic Mass Spectrometry Laboratory (LSMBO), IPHC, Université de Strasbourg, 25 Rue Becquerel, 67087 Strasbourg, France.,the IPHC, CNRS, UMR7178, 67087 Strasbourg, France, and
| | - Tchilabalo Dilezitoko Alayi
- the BioOrganic Mass Spectrometry Laboratory (LSMBO), IPHC, Université de Strasbourg, 25 Rue Becquerel, 67087 Strasbourg, France.,the IPHC, CNRS, UMR7178, 67087 Strasbourg, France, and
| | - Thomas Epting
- From the Institute for Clinical Chemistry and Laboratory Medicine, University Medical Center, Hugstetterstrasse 55, D-79106 Freiburg, Germany
| | - Karl Winkler
- From the Institute for Clinical Chemistry and Laboratory Medicine, University Medical Center, Hugstetterstrasse 55, D-79106 Freiburg, Germany
| | | | - Jayashree Soman
- the BioSciences Department, Rice University, Houston, Texas 77281
| | - Ivan Birukou
- the BioSciences Department, Rice University, Houston, Texas 77281
| | - Premila P Samuel
- the BioSciences Department, Rice University, Houston, Texas 77281
| | - John S Olson
- the BioSciences Department, Rice University, Houston, Texas 77281
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15
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Lepeshkevich SV, Gilevich SN, Parkhats MV, Dzhagarov BM. Molecular oxygen migration through the xenon docking sites of human hemoglobin in the R-state. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:1110-1121. [DOI: 10.1016/j.bbapap.2016.06.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 06/03/2016] [Accepted: 06/06/2016] [Indexed: 11/25/2022]
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16
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Esquerra RM, Bibi BM, Tipgunlakant P, Birukou I, Soman J, Olson JS, Kliger DS, Goldbeck RA. Role of Heme Pocket Water in Allosteric Regulation of Ligand Reactivity in Human Hemoglobin. Biochemistry 2016; 55:4005-17. [PMID: 27355904 PMCID: PMC4978812 DOI: 10.1021/acs.biochem.6b00081] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Water molecules can enter the heme pockets of unliganded myoglobins and hemoglobins, hydrogen bond with the distal histidine, and introduce steric barriers to ligand binding. The spectrokinetics of photodissociated CO complexes of human hemoglobin and its isolated α and β chains were analyzed for the effect of heme hydration on ligand rebinding. A strong coupling was observed between heme hydration and quaternary state. This coupling may contribute significantly to the 20-60-fold difference between the R- and T-state bimolecular CO binding rate constants and thus to the modulation of ligand reactivity that is the hallmark of hemoglobin allostery. Heme hydration proceeded over the course of several kinetic phases in the tetramer, including the R to T quaternary transition. An initial 150 ns hydration phase increased the R-state distal pocket water occupancy, nw(R), to a level similar to that of the isolated α (∼60%) and β (∼10%) chains, resulting in a modest barrier to ligand binding. A subsequent phase, concurrent with the first step of the R → T transition, further increased the level of heme hydration, increasing the barrier. The final phase, concurrent with the final step of the allosteric transition, brought the water occupancy of the T-state tetramer, nw(T), even higher and close to full occupancy in both the α and β subunits (∼90%). This hydration level could present an even larger barrier to ligand binding and contribute significantly to the lower iron reactivity of the T state toward CO.
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Affiliation(s)
- Raymond M. Esquerra
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco, California 94132, United States
| | - Bushra M. Bibi
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco, California 94132, United States
| | - Pooncharas Tipgunlakant
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco, California 94132, United States
| | - Ivan Birukou
- Department of Biochemistry and Cell Biology and W. M. Keck Center for Computational Biology, Rice University, Houston, Texas 77005, United States
| | - Jayashree Soman
- Department of Biochemistry and Cell Biology and W. M. Keck Center for Computational Biology, Rice University, Houston, Texas 77005, United States
| | - John S. Olson
- Department of Biochemistry and Cell Biology and W. M. Keck Center for Computational Biology, Rice University, Houston, Texas 77005, United States
| | - David S. Kliger
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States
| | - Robert A. Goldbeck
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States
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17
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Experiments on Hemoglobin in Single Crystals and Silica Gels Distinguish among Allosteric Models. Biophys J 2015; 109:1264-72. [PMID: 26038112 DOI: 10.1016/j.bpj.2015.04.037] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 04/24/2015] [Indexed: 01/14/2023] Open
Abstract
Trapping quaternary structures of hemoglobin in single crystals or by encapsulation in silica gels has provided a demanding set of data to test statistical mechanical models of allostery. In this work, we compare the results of those experiments with predictions of the four major allosteric models for hemoglobin: the quaternary two-state model of Monod, Wyman, and Changeux; the tertiary two-state model of Henry et al., which is the simplest extension of the Monod-Wyman-Changeux model to include pre-equilibria of tertiary as well as quaternary conformations; the structure-based model of Szabo and Karplus; and the modification of the latter model by Lee and Karplus. We show that only the tertiary two-state model can provide a near quantitative explanation of the single-crystal and gel experimental results.
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18
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Experimental basis for a new allosteric model for multisubunit proteins. Proc Natl Acad Sci U S A 2014; 111:12758-63. [PMID: 25139985 DOI: 10.1073/pnas.1413566111] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Monod, Wyman, and Changeux (MWC) explained allostery in multisubunit proteins with a widely applied theoretical model in which binding of small molecules, so-called allosteric effectors, affects reactivity by altering the equilibrium between more reactive (R) and less reactive (T) quaternary structures. In their model, each quaternary structure has a single reactivity. Here, we use silica gels to trap protein conformations and a new kind of laser photolysis experiment to show that hemoglobin, the paradigm of allostery, exhibits two ligand binding phases with the same fast and slow rates in both R and T quaternary structures. Allosteric effectors change the fraction of each phase but not the rates. These surprising results are readily explained by the simplest possible extension of the MWC model to include a preequilibrium between two tertiary conformations that have the same functional properties within each quaternary structure. They also have important implications for the long-standing question of a structural explanation for the difference in hemoglobin oxygen affinity of the two quaternary structures.
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19
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Jones EM, Monza E, Balakrishnan G, Blouin GC, Mak PJ, Zhu Q, Kincaid JR, Guallar V, Spiro TG. Differential control of heme reactivity in alpha and beta subunits of hemoglobin: a combined Raman spectroscopic and computational study. J Am Chem Soc 2014; 136:10325-39. [PMID: 24991732 PMCID: PMC4353013 DOI: 10.1021/ja503328a] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Indexed: 12/05/2022]
Abstract
The use of hybrid hemoglobin (Hb), with mesoheme substituted for protoheme, allows separate monitoring of the α or β hemes along the allosteric pathway. Using resonance Raman (rR) spectroscopy in silica gel, which greatly slows protein motions, we have observed that the Fe-histidine stretching frequency, νFeHis, which is a monitor of heme reactivity, evolves between frequencies characteristic of the R and T states, for both α or β chains, prior to the quaternary R-T and T-R shifts. Computation of νFeHis, using QM/MM and the conformational search program PELE, produced remarkable agreement with experiment. Analysis of the PELE structures showed that the νFeHis shifts resulted from heme distortion and, in the α chain, Fe-His bond tilting. These results support the tertiary two-state model of ligand binding (Henry et al., Biophys. Chem. 2002, 98, 149). Experimentally, the νFeHis evolution is faster for β than for α chains, and pump-probe rR spectroscopy in solution reveals an inflection in the νFeHis time course at 3 μs for β but not for α hemes, an interval previously shown to be the first step in the R-T transition. In the α chain νFeHis dropped sharply at 20 μs, the final step in the R-T transition. The time courses are fully consistent with recent computational mapping of the R-T transition via conjugate peak refinement by Karplus and co-workers (Fischer et al., Proc. Natl. Acad. Sci. U. S. A. 2011, 108, 5608). The effector molecule IHP was found to lower νFeHis selectively for α chains within the R state, and a binding site in the α1α2 cleft is suggested.
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Affiliation(s)
- Eric M. Jones
- Department
of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - Emanuele Monza
- Joint
BSC-IRB Research Program in Computational Biology, Barcelona Supercomputing Center, c/Jordi Girona 29, 08034 Barcelona, Spain
| | - Gurusamy Balakrishnan
- Department
of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - George C. Blouin
- Department
of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - Piotr J. Mak
- Department
of Chemistry, Marquette University, Milwaukee, Wisconsin 53233, United States
| | - Qianhong Zhu
- Department
of Chemistry, Marquette University, Milwaukee, Wisconsin 53233, United States
| | - James R. Kincaid
- Department
of Chemistry, Marquette University, Milwaukee, Wisconsin 53233, United States
| | - Victor Guallar
- Joint
BSC-IRB Research Program in Computational Biology, Barcelona Supercomputing Center, c/Jordi Girona 29, 08034 Barcelona, Spain
- Institució
Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys 23, 08010 Barcelona, Spain
| | - Thomas G. Spiro
- Department
of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
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20
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Yamada K, Ishikawa H, Mizuno M, Shibayama N, Mizutani Y. Intersubunit Communication via Changes in Hemoglobin Quaternary Structures Revealed by Time-Resolved Resonance Raman Spectroscopy: Direct Observation of the Perutz Mechanism. J Phys Chem B 2013; 117:12461-8. [DOI: 10.1021/jp407735t] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Kenta Yamada
- Department
of Chemistry, Graduate School of Science, Osaka University, 1-1
Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Haruto Ishikawa
- Department
of Chemistry, Graduate School of Science, Osaka University, 1-1
Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Misao Mizuno
- Department
of Chemistry, Graduate School of Science, Osaka University, 1-1
Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Naoya Shibayama
- Department of Physiology, Division of Biophysics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan
| | - Yasuhisa Mizutani
- Department
of Chemistry, Graduate School of Science, Osaka University, 1-1
Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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21
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Ronda L, Bettati S, Henry ER, Kashav T, Sanders JM, Royer WE, Mozzarelli A. Tertiary and quaternary allostery in tetrameric hemoglobin from Scapharca inaequivalvis. Biochemistry 2013; 52:2108-17. [PMID: 23458680 DOI: 10.1021/bi301620x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The clam Scapharca inaequivalvis possesses two cooperative oxygen binding hemoglobins in its red cells: a homodimeric HbI and a heterotetrameric A2B2 HbII. Each AB dimeric half of HbII is assembled in a manner very similar to that of the well-studied HbI. This study presents crystal structures of HbII along with oxygen binding data both in the crystalline state and in wet nanoporous silica gels. Despite very similar ligand-linked structural transitions observed in HbI and HbII crystals, HbII in the crystal or encapsulated in silica gels apparently exhibits minimal cooperativity in oxygen binding, in contrast with the full cooperativity exhibited by HbI crystals. However, oxygen binding curves in the crystal indicate the presence of a significant functional inequivalence of A and B chains. When this inequivalence is taken into account, both crystal and R state gel functional data are consistent with the conservation of a tertiary contribution to cooperative oxygen binding, quantitatively similar to that measured for HbI, and are in keeping with the structural information. Furthermore, our results indicate that to fully express cooperative ligand binding, HbII requires quaternary transitions hampered by crystal lattice and gel encapsulation, revealing greater complexity in cooperative function than the direct communication across a dimeric interface observed in HbI.
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Affiliation(s)
- Luca Ronda
- Department of Pharmacy, University of Parma , Parco Area delle Scienze, 23/A, 43124 Parma, Italy
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22
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Smith EA, Newland P, Bestwick KG, Ahmed N. Increased whole blood manganese concentrations observed in children with iron deficiency anaemia. J Trace Elem Med Biol 2013; 27:65-9. [PMID: 22940083 DOI: 10.1016/j.jtemb.2012.07.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Revised: 05/30/2012] [Accepted: 07/02/2012] [Indexed: 12/01/2022]
Abstract
A prospective observational study was carried out at Alder Hey Children's Hospital, Liverpool, England, UK on children aged 1-6 years attending the pathology department for routine blood tests (n=225). Whole blood manganese concentrations were measured plus the following markers of iron status; haemoglobin, MCV, MCH, RBC count, ferritin, transferrin saturation and soluble transferrin receptors. Multiple regression analysis was performed, with blood manganese as the dependent variable and factors of iron status, age and gender as independent variables. A strong relationship between blood manganese and iron deficiency was demonstrated (adjusted R(2)=34.3%, p<0.001) and the primary contributing factors to this relationship were haematological indices and soluble transferrin receptors. Subjects were categorised according to iron status using serum ferritin, transferrin saturation and haemoglobin indices. Children with iron deficiency anaemia had higher median blood manganese concentrations (16.4 μg/L, range 11.7-42.4, n=20) than children with iron sufficiency (11 μg/L, range 5.9-20.9, n=59, p<0.001). This suggests that children with iron deficiency anaemia may be at risk from manganese toxicity (whole blood manganese >20 μg/L), and that this may lead to neurological problems. Treatment of iron deficiency in children is important both to improve iron status and to reduce the risk of manganese toxicity.
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Affiliation(s)
- Elisabeth Anne Smith
- Department of Clinical Biochemistry, Alder Hey Children's Foundation Trust, Liverpool, England L12 2AP, UK.
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23
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Farina M, Avila DS, da Rocha JBT, Aschner M. Metals, oxidative stress and neurodegeneration: a focus on iron, manganese and mercury. Neurochem Int 2012; 62:575-94. [PMID: 23266600 DOI: 10.1016/j.neuint.2012.12.006] [Citation(s) in RCA: 343] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2012] [Revised: 12/07/2012] [Accepted: 12/10/2012] [Indexed: 02/08/2023]
Abstract
Essential metals are crucial for the maintenance of cell homeostasis. Among the 23 elements that have known physiological functions in humans, 12 are metals, including iron (Fe) and manganese (Mn). Nevertheless, excessive exposure to these metals may lead to pathological conditions, including neurodegeneration. Similarly, exposure to metals that do not have known biological functions, such as mercury (Hg), also present great health concerns. This review focuses on the neurodegenerative mechanisms and effects of Fe, Mn and Hg. Oxidative stress (OS), particularly in mitochondria, is a common feature of Fe, Mn and Hg toxicity. However, the primary molecular targets triggering OS are distinct. Free cationic iron is a potent pro-oxidant and can initiate a set of reactions that form extremely reactive products, such as OH. Mn can oxidize dopamine (DA), generating reactive species and also affect mitochondrial function, leading to accumulation of metabolites and culminating with OS. Cationic Hg forms have strong affinity for nucleophiles, such as -SH and -SeH. Therefore, they target critical thiol- and selenol-molecules with antioxidant properties. Finally, we address the main sources of exposure to these metals, their transport mechanisms into the brain, and therapeutic modalities to mitigate their neurotoxic effects.
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Affiliation(s)
- Marcelo Farina
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, 88040-900 Florianópolis, SC, Brazil
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24
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Tsai AL, Martin E, Berka V, Olson JS. How do heme-protein sensors exclude oxygen? Lessons learned from cytochrome c', Nostoc puntiforme heme nitric oxide/oxygen-binding domain, and soluble guanylyl cyclase. Antioxid Redox Signal 2012; 17:1246-63. [PMID: 22356101 PMCID: PMC3430480 DOI: 10.1089/ars.2012.4564] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
SIGNIFICANCE Ligand selectivity for dioxygen (O(2)), carbon monoxide (CO), and nitric oxide (NO) is critical for signal transduction and is tailored specifically for each heme-protein sensor. Key NO sensors, such as soluble guanylyl cyclase (sGC), specifically recognized low levels of NO and achieve a total O(2) exclusion. Several mechanisms have been proposed to explain the O(2) insensitivity, including lack of a hydrogen bond donor and negative electrostatic fields to selectively destabilize bound O(2), distal steric hindrance of all bound ligands to the heme iron, and restriction of in-plane movements of the iron atom. RECENT ADVANCES Crystallographic structures of the gas sensors, Thermoanaerobacter tengcongensis heme-nitric oxide/oxygen-binding domain (Tt H-NOX(1)) or Nostoc puntiforme (Ns) H-NOX, and measurements of O(2) binding to site-specific mutants of Tt H-NOX and the truncated β subunit of sGC suggest the need for a H-bonding donor to facilitate O(2) binding. CRITICAL ISSUES However, the O(2) insensitivity of full length sGC with a site-specific replacement of isoleucine by a tyrosine on residue 145 and the very slow autooxidation of Ns H-NOX and cytochrome c' suggest that more complex mechanisms have evolved to exclude O(2) but retain high affinity NO binding. A combined graphical analysis of ligand binding data for libraries of heme sensors, globins, and model heme shows that the NO sensors dramatically inhibit the formation of six-coordinated NO, CO, and O(2) complexes by direct distal steric hindrance (cyt c'), proximal constraints of in-plane iron movement (sGC), or combinations of both following a sliding scale rule. High affinity NO binding in H-NOX proteins is achieved by multiple NO binding steps that produce a high affinity five-coordinate NO complex, a mechanism that also prevents NO dioxygenation. FUTURE DIRECTIONS Knowledge advanced by further extensive test of this "sliding scale rule" hypothesis should be valuable in guiding novel designs for heme based sensors.
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Affiliation(s)
- Ah-Lim Tsai
- Division of Hematology, University of Texas Health Science Center at Houston, Houston, Texas 77225, USA.
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25
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Mollan TL, Abraham B, Strader MB, Jia Y, Lozier JN, Olson JS, Alayash AI. Familial secondary erythrocytosis due to increased oxygen affinity is caused by destabilization of the T state of hemoglobin Brigham (α₂β₂(Pro100Leu)). Protein Sci 2012; 21:1444-55. [PMID: 22821886 DOI: 10.1002/pro.2130] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Revised: 06/19/2012] [Accepted: 07/12/2012] [Indexed: 02/02/2023]
Abstract
Hemoglobin Brigham (β Pro100 to Leu) was first reported in a patient with familial erythrocytosis. Erythrocytes of an affected individual from the same family contain both HbA and Hb Brigham and exhibit elevated O₂ affinity compared with normal cells (P₅₀ = 23 mm Hg vs. 31 mmHg at pH 7.4 at 37°C). O₂ affinities measured for hemolysates were sensitive to changes in pH or chloride concentrations, indicating little change in the Bohr and Chloride effects. Hb Brigham was separated from normal HbA by nondenaturing cation exchange liquid chromatography, and the amino acid substitution was verified by mass spectrometry. The properties of Hb Brigham isolated from the patient's blood were then compared with those of recombinant Hb Brigham expressed in Escherichia coli. Kinetic experiments suggest that the rate constants for ligand binding and release in the high (R) and low (T) affinity quaternary states of Hb Brigham are similar to those of native hemoglobin. However, the Brigham mutation decreases the T to R equilibrium constant (L) which accelerates the switch to the R state during ligand binding to deoxy-Hb, increasing the rate of association by approximately twofold, and decelerates the switch during ligand dissociation from HbO₂, decreasing the rate approximately twofold. These kinetic data help explain the high O₂ affinity characteristics of Hb Brigham and provide further evidence for the importance of the contribution of Pro100 to intersubunit contacts and stabilization of the T quaternary structure.
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Affiliation(s)
- Todd L Mollan
- Laboratory of Biochemistry and Vascular Biology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA
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26
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Shibayama N. Symmetry distortion in the human hemoglobin tetramer induced by asymmetric ligation. FEBS Lett 2011; 586:74-8. [DOI: 10.1016/j.febslet.2011.11.027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 11/23/2011] [Accepted: 11/23/2011] [Indexed: 10/14/2022]
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27
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Lepeshkevich SV, Biziuk SA, Lemeza AM, Dzhagarov BM. The kinetics of molecular oxygen migration in the isolated α chains of human hemoglobin as revealed by molecular dynamics simulations and laser kinetic spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:1279-88. [DOI: 10.1016/j.bbapap.2011.06.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Revised: 06/16/2011] [Accepted: 06/24/2011] [Indexed: 10/18/2022]
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28
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Shibayama N, Sugiyama K, Park SY. Structures and oxygen affinities of crystalline human hemoglobin C (β6 Glu->Lys) in the R and R2 quaternary structures. J Biol Chem 2011; 286:33661-8. [PMID: 21816820 DOI: 10.1074/jbc.m111.266056] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recent crystallographic studies suggested that fully liganded human hemoglobin can adopt multiple quaternary conformations that include the two previously solved relaxed conformations, R and R2, whereas fully unliganded deoxyhemoglobin may adopt only one T (tense) quaternary conformation. An important unanswered question is whether R, R2, and other relaxed quaternary conformations represent different physiological states with different oxygen affinities. Here, we answer this question by showing the oxygen equilibrium curves of single crystals of human hemoglobin in the R and R2 state. In this study, we have used a naturally occurring mutant hemoglobin C (β6 Glu→Lys) to stabilize the R and R2 crystals. Additionally, we have refined the x-ray crystal structure of carbonmonoxyhemoglobin C, in the R and R2 state, to 1.4 and 1.8 Å resolution, respectively, to compare precisely the structures of both types of relaxed states. Despite the large quaternary structural difference between the R and R2 state, both crystals exhibit similar noncooperative oxygen equilibrium curves with a very high affinity for oxygen, comparable with the fourth oxygen equilibrium constant (K(4)) of human hemoglobin in solution. One small difference is that the R2 crystals have an oxygen affinity that is 2-3 times higher than that of the R crystals. These results demonstrate that the functional difference between the two typical relaxed quaternary conformations is small and physiologically less important, indicating that these relaxed conformations simply reflect a structural polymorphism of a high affinity relaxed state.
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Affiliation(s)
- Naoya Shibayama
- Department of Physiology, Division of Biophysics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan.
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29
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Crowley MA, Mollan TL, Abdulmalik OY, Butler AD, Goodwin EF, Sarkar A, Stolle CA, Gow AJ, Olson JS, Weiss MJ. A hemoglobin variant associated with neonatal cyanosis and anemia. N Engl J Med 2011; 364:1837-43. [PMID: 21561349 PMCID: PMC3632254 DOI: 10.1056/nejmoa1013579] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Globin-gene mutations are a rare but important cause of cyanosis. We identified a missense mutation in the fetal Gγ-globin gene (HBG2) in a father and daughter with transient neonatal cyanosis and anemia. This new mutation modifies the ligand-binding pocket of fetal hemoglobin by means of two mechanisms. First, the relatively large side chain of methionine decreases both the affinity of oxygen for binding to the mutant hemoglobin subunit and the rate at which it does so. Second, the mutant methionine is converted to aspartic acid post-translationally, probably through oxidative mechanisms. The presence of this polar amino acid in the heme pocket is predicted to enhance hemoglobin denaturation, causing anemia.
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Affiliation(s)
- Moira A Crowley
- Division of Neonatology, Case Western Reserve University, Cleveland, USA
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30
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Birukou I, Soman J, Olson JS. Blocking the gate to ligand entry in human hemoglobin. J Biol Chem 2010; 286:10515-29. [PMID: 21193395 DOI: 10.1074/jbc.m110.176271] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
His(E7) to Trp replacements in HbA lead to markedly biphasic bimolecular CO rebinding after laser photolysis. For isolated mutant subunits, the fraction of fast phase increases with increasing [CO], suggesting a competition between binding to an open conformation with an empty E7 channel and relaxation to blocked or closed, slowly reacting states. The rate of conformational relaxation of the open state is ∼18,000 s(-1) in α subunits and ∼10-fold faster in β subunits, ∼175,000 s(-1). Crystal structures were determined for tetrameric α(WT)β(Trp-63) HbCO, α(Trp-58)β(WT) deoxyHb, and Trp-64 deoxy- and CO-Mb as controls. In Trp-63(E7) βCO, the indole side chain is located in the solvent interface, blocking entry into the E7 channel. Similar blocked Trp-64(E7) conformations are observed in the mutant Mb crystal structures. In Trp-58(E7) deoxy-α subunits, the indole side chain fills both the channel and the distal pocket, forming a completely closed state. The bimolecular rate constant for CO binding, k'(CO), to the open conformations of both mutant Hb subunits is ∼80-90 μm(-1) s(-1), whereas k'(CO) for the completely closed states is 1000-fold slower, ∼0.08 μm(-1) s(-1). A transient intermediate with k'(CO) ≈ 0.7 μm(-1) s(-1) is observed after photolysis of Trp-63(E7) βCO subunits and indicates that the indole ring blocks the entrance to the E7 channel, as observed in the crystal structures of Trp(E7) deoxyMb and βCO subunits. Thus, either blocking or completely filling the E7 channel dramatically slows bimolecular binding, providing strong evidence that the E7 channel is the major pathway (≥90%) for ligand entry in human hemoglobin.
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Affiliation(s)
- Ivan Birukou
- Department of Biochemistry and Cell Biology and the W. M. Keck Center for Computational Biology, Rice University, Houston, Texas 77005, USA
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31
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Shibata T, Nagao S, Tai H, Nagatomo S, Hamada H, Yoshikawa H, Suzuki A, Yamamoto Y. Characterization of the acid–alkaline transition in the individual subunits of human adult and foetal methaemoglobins. J Biochem 2010; 148:217-29. [DOI: 10.1093/jb/mvq055] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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32
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Birukou I, Schweers RL, Olson JS. Distal histidine stabilizes bound O2 and acts as a gate for ligand entry in both subunits of adult human hemoglobin. J Biol Chem 2010; 285:8840-54. [PMID: 20080971 PMCID: PMC2838306 DOI: 10.1074/jbc.m109.053934] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2009] [Revised: 01/13/2010] [Indexed: 11/06/2022] Open
Abstract
The role of the distal histidine in regulating ligand binding to adult human hemoglobin (HbA) was re-examined systematically by preparing His(E7) to Gly, Ala, Leu, Gln, Phe, and Trp mutants of both Hb subunits. Rate constants for O(2), CO, and NO binding were measured using rapid mixing and laser photolysis experiments designed to minimize autoxidation of the unstable apolar E7 mutants. Replacing His(E7) with Gly, Ala, Leu, or Phe causes 20-500-fold increases in the rates of O(2) dissociation from either Hb subunit, demonstrating unambiguously that the native His(E7) imidazole side chain forms a strong hydrogen bond with bound O(2) in both the alpha and beta chains (DeltaG(His(E7)H-bond) approximately -8 kJ/mol). As the size of the E7 amino acid is increased from Gly to Phe, decreases in k(O2)', k(NO)', and calculated bimolecular rates of CO entry (k(entry)') are observed. Replacing His(E7) with Trp causes further decreases in k(O2)', k(NO)', and k(entry)' to 1-2 microM(-1) s(-1) in beta subunits, whereas ligand rebinding to alphaTrp(E7) subunits after photolysis is markedly biphasic, with fast k(O2)', k(CO)', and k(NO)' values approximately 150 microM(-1) s(-1) and slow rate constants approximately 0.1 to 1 microM(-1) s(-1). Rapid bimolecular rebinding to an open alpha subunit conformation occurs immediately after photolysis of the alphaTrp(E7) mutant at high ligand concentrations. However, at equilibrium the closed alphaTrp(E7) side chain inhibits the rate of ligand binding >200-fold. These data suggest strongly that the E7 side chain functions as a gate for ligand entry in both HbA subunits.
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Affiliation(s)
- Ivan Birukou
- From the Department of Biochemistry and Cell Biology and the W. M. Keck Center for Computational Biology, Rice University, Houston, Texas 77005
| | - Rachel L. Schweers
- From the Department of Biochemistry and Cell Biology and the W. M. Keck Center for Computational Biology, Rice University, Houston, Texas 77005
| | - John S. Olson
- From the Department of Biochemistry and Cell Biology and the W. M. Keck Center for Computational Biology, Rice University, Houston, Texas 77005
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33
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Dzhagarov BM, Lepeshkevich SV. Photonics of the hemoglobin active site. HIGH ENERGY CHEMISTRY 2010. [DOI: 10.1134/s0018143910020074] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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34
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Lepeshkevich SV, Parkhats MV, Stepuro II, Dzhagarov BM. Molecular oxygen binding with α and β subunits within the R quaternary state of human hemoglobin in solutions and porous sol–gel matrices. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2009; 1794:1823-30. [DOI: 10.1016/j.bbapap.2009.08.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2009] [Revised: 08/18/2009] [Accepted: 08/19/2009] [Indexed: 11/28/2022]
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35
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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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36
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Asmundson AL, Taber AM, van der Walde A, Lin DH, Olson JS, Anthony-Cahill SJ. Coexpression of human alpha- and circularly permuted beta-globins yields a hemoglobin with normal R state but modified T state properties. Biochemistry 2009; 48:5456-65. [PMID: 19397368 DOI: 10.1021/bi900216p] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
For the first time, a circularly permuted human beta-globin (cpbeta) has been coexpressed with human alpha-globin in bacterial cells and shown to associate to form alpha-cpbeta hemoglobin in solution. Flash photolysis studies of alpha-cpbeta show markedly biphasic CO and O(2) kinetics with the amplitudes for the fast association phases being dominant due the presence of large amounts of high-affinity liganded hemoglobin dimers. Extensive dimerization of liganded but not deoxygenated alpha-cpbeta was observed by gel chromatography. The rate constants for O(2) and CO binding to the R state forms of alpha-cpbeta are almost identical to those of native HbA (k'(R(CO)) approximately 5.0 microM(-1) s(-1); k'(R(O(2))) approximately 50 microM(-1) s(-1)), and the rate of O(2) dissociation from fully oxygenated alpha-cpbeta is also very similar to that observed for HbA (k(R(O(2))) approximately 21-28 s(-1)). When the equilibrium deoxyHb form of alpha-cpbeta is reacted with CO in rapid mixing experiments, the observed time courses are monophasic and the observed bimolecular association rate constant is approximately 1.0 microM(-1) s(-1), which is intermediate between the R state rate measured in partial photolysis experiments (approximately 5 microM(-1) s(-1)) and that observed for T state deoxyHbA (k'(T(CO)) approximately 0.1 to 0.2 microM(-1) s(-1)). Thus the deoxygenated permutated beta subunits generate an intermediate, higher affinity, deoxyHb quaternary state. This conclusion is supported by equilibrium oxygen binding measurements in which alpha-cpbeta exhibits a P(50) of approximately 1.5 mmHg and a low n-value (approximately 1.3) at pH 7, 20 degrees C, compared to 8.5 mmHg and n approximately 2.8 for native HbA under identical, dilute conditions.
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Affiliation(s)
- Anna L Asmundson
- Department of Chemistry, Western Washington University, Bellingham, Washington 98225-9150, USA
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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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38
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Balakrishnan G, Zhao X, Podstawska E, Proniewicz LM, Kincaid JR, Spiro TG. Subunit-selective interrogation of CO recombination in carbonmonoxy hemoglobin by isotope-edited time-resolved resonance Raman spectroscopy. Biochemistry 2009; 48:3120-6. [PMID: 19245215 PMCID: PMC2722936 DOI: 10.1021/bi802190f] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hemoglobin (Hb) is an allosteric tetrameric protein made up of alphabeta heterodimers. The alpha and beta chains are similar, but are chemically and structurally distinct. To investigate dynamical differences between the chains, we have prepared tetramers in which the chains are isotopically distinguishable, via reconstitution with (15)N-heme. Ligand recombination and heme structural evolution, following HbCO dissociation, was monitored with chain selectivity by resonance Raman (RR) spectroscopy. For alpha but not for beta chains, the frequency of the nu(4) porphyrin breathing mode increased on the microsecond time scale. This increase is a manifestation of proximal tension in the Hb T-state, and its time course is parallel to the formation of T contacts, as determined previously by UVRR spectroscopy. Despite the localization of proximal constraint in the alpha chains, geminate recombination was found to be equally probable in the two chains, with yields of 39 +/- 2%. We discuss the possibility that this equivalence is coincidental, in the sense that it arises from the evolutionary pressure for cooperativity, or that it reflects mechanical coupling across the alphabeta interface, evidence for which has emerged from UVRR studies of site mutants.
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Affiliation(s)
| | - Xiaojie Zhao
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Edyta Podstawska
- Department of Chemistry, Marquette University, Milwaukee, WI 53233, USA
- Department of Chemistry, Jagiellonian University, Krakow, Poland
| | - Leonard M. Proniewicz
- Department of Chemistry, Marquette University, Milwaukee, WI 53233, USA
- Department of Chemistry, Jagiellonian University, Krakow, Poland
| | - James R. Kincaid
- Department of Chemistry, Marquette University, Milwaukee, WI 53233, USA
| | - Thomas G. Spiro
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
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39
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Maillett DH, Simplaceanu V, Shen TJ, Ho NT, Olson JS, Ho C. Interfacial and distal-heme pocket mutations exhibit additive effects on the structure and function of hemoglobin. Biochemistry 2008; 47:10551-63. [PMID: 18788751 DOI: 10.1021/bi800816v] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein engineering strategies seek to develop a hemoglobin-based oxygen carrier with optimized functional properties, including (i) an appropriate O 2 affinity, (ii) high cooperativity, (iii) limited NO reactivity, and (iv) a diminished rate of auto-oxidation. The mutations alphaL29F, alphaL29W, alphaV96W and betaN108K individually impart some of these traits and in combinations produce hemoglobin molecules with interesting ligand-binding and allosteric properties. Studies of the ligand-binding properties and solution structures of single and multiple mutants have been performed. The aromatic side chains placed in the distal-heme pocket environment affect the intrinsic ligand-binding properties of the mutated subunit itself, beyond what can be explained by allostery, and these changes are accompanied by local structural perturbations. In contrast, hemoglobins with mutations in the alpha 1beta 1 and alpha 1beta 2 interfaces display functional properties of both "R"- and "T"-state tetramers because the equilibrium between quaternary states is altered. These mutations are accompanied by global structural perturbations, suggesting an indirect, allostery-driven cause for their effects. Combinations of the distal-heme pocket and interfacial mutations exhibit additive effects in both structural and functional properties, contribute to our understanding of allostery, and advance protein-engineering methods for manipulating the O 2 binding properties of the hemoglobin molecule.
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Affiliation(s)
- David H Maillett
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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Vandegriff KD, Young MA, Lohman J, Bellelli A, Samaja M, Malavalli A, Winslow RM. CO-MP4, a polyethylene glycol-conjugated haemoglobin derivative and carbon monoxide carrier that reduces myocardial infarct size in rats. Br J Pharmacol 2008; 154:1649-61. [PMID: 18536756 DOI: 10.1038/bjp.2008.219] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE MP4 (Hemospan) is a Hb-based oxygen therapeutic agent, based on polyethylene-glycol (PEG) conjugation to Hb, undergoing clinical trials as an oxygen carrier. This study describes the functional interaction between MP4 and carbon monoxide (CO), as a CO delivery agent, and the effects of CO-MP4 on myocardial infarct size following ischaemia and reperfusion in rats. EXPERIMENTAL APPROACH Kinetic measurements of CO-MP4 binding were used to evaluate the effects of PEG modification on Hb subunit structure/function and to calculate CO-MP4 equilibrium constants. CO transport by CO-MP4 was shown by ligand (O2/CO) partitioning between MP4 and red blood cell (RBC)-Hb. Pharmacological effects of CO-MP4 were studied on myocardial infarction in rats. KEY RESULTS CO binding kinetics show primary structural/functional effects on beta chains in MP4, with alpha chains maintaining the ability to undergo tertiary conformational transition. CO confers long-term, room-temperature stability and is able to rapidly re-equilibrate between MP4 and RBCs. In a rat model of myocardial infarct, in contrast to oxy-MP4, CO-MP4 reduced infarct size when administered prior to the induction of ischaemia. CONCLUSIONS AND IMPLICATIONS MP4 PEGylation chemistry modifies the individual function of Hb subunits, but results in an overall CO equilibrium constant similar to that for unmodified Hb. CO-MP4 is able to deliver CO to the circulation and reduces ischaemia/reperfusion injury in rats, providing the first evidence for this drug as a CO therapeutic agent.
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Ciaccio C, Coletta A, De Sanctis G, Marini S, Coletta M. Cooperativity and allostery in haemoglobin function. IUBMB Life 2008; 60:112-23. [DOI: 10.1002/iub.6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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42
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Abstract
Understanding the molecular mechanism of hemoglobin cooperativity remains an enduring challenge. Protein forces that control ligand affinity are not directly accessible by experiment. We demonstrate that computational quantum mechanics/molecular mechanics methods can provide reasonable values of ligand binding energies in Hb, and of their dependence on allostery. About 40% of the binding energy differences between the relaxed state and tense state quaternary structures result from strain induced in the heme and its ligands, especially in one of the pyrrole rings. The proximal histidine also contributes significantly, in particular, in the alpha-chains. The remaining energy difference resides in protein contacts, involving residues responsible for locking the quaternary changes. In the alpha-chains, the most important contacts involve the FG corner, at the "hinge" region of the alpha(1)beta(2) quaternary interface. The energy differences are spread more evenly among the beta-chain residues, suggesting greater flexibility for the beta- than for the alpha-chains along the quaternary transition. Despite this chain differentiation, the chains contribute equally to the relaxed substitute state energy difference. Thus, nature has evolved a symmetric response to the quaternary structure change, which is a requirement for maximum cooperativity, via different mechanisms for the two kinds of chains.
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Samuni U, Roche CJ, Dantsker D, Friedman JM. Conformational dependence of hemoglobin reactivity under high viscosity conditions: the role of solvent slaved dynamics. J Am Chem Soc 2007; 129:12756-64. [PMID: 17910446 DOI: 10.1021/ja072342b] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The concept of protein dynamic states is introduced. This concept is based on (i) protein dynamics being organized hierarchically with respect to solvent slaving and (ii) which tier of dynamics is operative over the time window of a given measurement. The protein dynamic state concept is used to analyze the kinetic phases derived from the recombination of carbon monoxide to sol-gel-encapsulated human adult hemoglobin (HbA) and select recombinant mutants. The temperature-dependent measurements are made under very high viscosity conditions obtained by bathing the samples in an excess of glycerol. The results are consistent with a given tier of solvent slaved dynamics becoming operative at a time delay (with respect to the onset of the measurement) that is primarily solvent- and temperature-dependent. However, the functional consequences of the dynamics are protein- and conformation-specific. The kinetic traces from both equilibrium populations and trapped allosteric intermediates show a consistent progression that exposes the role of both conformation and hydration in the control of reactivity. Iron-zinc symmetric hybrid forms of HbA are used to show the dramatic difference between the kinetic patterns for T state alpha and beta subunits. The overall results support a model for allostery in HbA in which the ligand-binding-induced transition from the deoxy T state to the high -affinity R state proceeds through a progression of T state intermediates.
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Affiliation(s)
- Uri Samuni
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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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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45
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Lepeshkevich SV, Dzhagarov BM. Mutual effects of proton and sodium chloride on oxygenation of liganded human hemoglobin. FEBS J 2005; 272:6109-19. [PMID: 16302974 DOI: 10.1111/j.1742-4658.2005.05008.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The different effects of pH and NaCl on individual O2-binding properties of alpha and beta subunits within liganded tetramer and dimer of human hemoglobin (HbA) were examined in a number of laser time-resolved spectroscopic measurements. A previously proposed approach [Dzhagarov BM & Lepeshkevich SV (2004) Chem Phys Lett390, 59-64] was used to determine the extent of subunit dissociation rate constant difference and subunit affinity difference from a single flash photolysis experiment. To investigate the effect of NaCl concentration on the association and dissociation rate constants we carried out a series of experiments at four different concentrations (0.1, 0.5, 1.0 and 2.0 m NaCl) over the pH range of the alkaline Bohr effect. As the data suggest, the individual properties of the alpha and beta subunits within the completely liganded tetrameric hemoglobin did not depend on pH under salt-free conditions. However, different effects NaCl on the individual kinetic properties of the alpha and beta subunits were revealed. Regulation of the O2-binding properties of the alpha and beta subunits within the liganded tetramer is proposed to be attained in two quite different ways.
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Affiliation(s)
- Sergei V Lepeshkevich
- Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, Minsk, Belarus
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46
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Ben-Tal A. Simplified models for gas exchange in the human lungs. J Theor Biol 2005; 238:474-95. [PMID: 16038941 DOI: 10.1016/j.jtbi.2005.06.005] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2004] [Revised: 05/31/2005] [Accepted: 06/03/2005] [Indexed: 11/26/2022]
Abstract
This paper presents a hierarchy of models with increasing complexity for gas exchange in the human lungs. The models span from a single compartment, inflexible lung to a single compartment, flexible lung with pulmonary gas exchange. It is shown how the models are related to well-known models in the literature. A long-term purpose of this work is to study nonlinear phenomena seen in the cardio-respiratory system (for example, synchronization between ventilation rate and heart rate, and Cheyne-Stokes respiration). The models developed in this paper can be regarded as the controlled system (plant) and provide a mathematical framework to link between "molecular-level", and "systems-level" models. It is shown how changes in molecular level affect the alveolar partial pressure. Two assumptions that have previously been made are re-examined: (1) the hidden assumption that the air flow through the mouth is equal to the rate of volume change in the lungs, and, (2) the assumption that the process of oxygen binding to hemoglobin is near equilibrium. Conditions under which these assumptions are valid are studied. All the parameters in the models, except two, are physiologically realistic. Numerical results are consistent with published experimental observations.
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Affiliation(s)
- Alona Ben-Tal
- Bioengineering Institute, University of Auckland, Private Bag 92019, Auckland, New Zealand.
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47
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Sottini S, Abbruzzetti S, Viappiani C, Bettati S, Ronda L, Mozzarelli A. Evidence for Two Geminate Rebinding States Following Laser Photolysis of R State Hemoglobin Encapsulated in Wet Silica Gels. J Phys Chem B 2005; 109:11411-3. [PMID: 16852394 DOI: 10.1021/jp0514224] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this letter we report the first experimental evidence for CO rebinding to human hemoglobin from multiple geminate states. The analysis of the rebinding kinetics using a maximum entropy method allowed the identification of two distinct rebinding states within the protein matrix, which become populated under conditions of increased viscosity in a silica gel at high glycerol concentration. Our findings suggest the presence of at least two distinct docking sites for the photolyzed ligand. Assuming a minimal four-state model, we estimate the microscopic rates and the activation energies for the elementary processes.
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48
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Lepeshkevich SV, Konovalova NV, Stepuro II, Dzhagarov BM. Kinetic studies of oxygenation of α- and β-subunits within pyridoxal 5′-phosphate derivatives of human hemoglobin. J Mol Struct 2005. [DOI: 10.1016/j.molstruc.2004.10.091] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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49
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Viappiani C, Bettati S, Bruno S, Ronda L, Abbruzzetti S, Mozzarelli A, Eaton WA. New insights into allosteric mechanisms from trapping unstable protein conformations in silica gels. Proc Natl Acad Sci U S A 2004; 101:14414-9. [PMID: 15385676 PMCID: PMC521967 DOI: 10.1073/pnas.0405987101] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2004] [Indexed: 11/18/2022] Open
Abstract
To understand why the classical two-state allosteric model of Monod, Wyman, and Changeux explains cooperative oxygen binding by hemoglobin but does not explain changes in oxygen affinity by allosteric inhibitors, we have investigated the kinetic properties of unstable conformations transiently trapped by encapsulation in silica gels. Conformational trapping reveals that after nanosecond photodissociation of carbon monoxide a large fraction of the subunits of the T quaternary structure has kinetic properties almost identical to those of subunits of the R quaternary structure. Addition of allosteric inhibitors reduces both the fraction of R-like subunits and the oxygen affinity of the T quaternary structure. These kinetic and equilibrium results are readily explained by a recently proposed generalization of the Monod-Wyman-Changeux model in which a pre-equilibrium between two functionally different tertiary, rather than quaternary, conformations plays the central role.
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50
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Dzhagarov B, Lepeshkevich S. Kinetic studies of differences between α- and β-chains of human hemoglobin: an approach for determination of the chain affinity to oxygen. Chem Phys Lett 2004. [DOI: 10.1016/j.cplett.2004.04.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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