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Schaunaman N, Cervantes D, Nichols T, Numata M, Ledford JG, Kraft M, Chu HW. Cooperation of immune regulators Tollip and surfactant protein A inhibits influenza A virus infection in mice. Respir Res 2024; 25:193. [PMID: 38702733 PMCID: PMC11068576 DOI: 10.1186/s12931-024-02820-3] [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: 03/26/2024] [Accepted: 04/23/2024] [Indexed: 05/06/2024] Open
Abstract
BACKGROUND Influenza A virus (IAV) infection is a significant risk factor for respiratory diseases, but the host defense mechanisms against IAV remain to be defined. Immune regulators such as surfactant protein A (SP-A) and Toll-interacting protein (Tollip) have been shown to be involved in IAV infection, but whether SP-A and Tollip cooperate in more effective host defense against IAV infection has not been investigated. METHODS Wild-type (WT), Tollip knockout (KO), SP-A KO, and Tollip/SP-A double KO (dKO) mice were infected with IAV for four days. Lung macrophages were isolated for bulk RNA sequencing. Precision-cut lung slices (PCLS) from WT and dKO mice were pre-treated with SP-A and then infected with IAV for 48 h. RESULTS Viral load was significantly increased in bronchoalveolar lavage (BAL) fluid of dKO mice compared to all other strains of mice. dKO mice had significantly less recruitment of neutrophils into the lung compared to Tollip KO mice. SP-A treatment of PCLS enhanced expression of TNF and reduced viral load in dKO mouse lung tissue. Pathway analysis of bulk RNA sequencing data suggests that macrophages from IAV-infected dKO mice reduced expression of genes involved in neutrophil recruitment, IL-17 signaling, and Toll-like receptor signaling. CONCLUSIONS Our data suggests that both Tollip and SP-A are essential for the lung to exert more effective innate defense against IAV infection.
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Affiliation(s)
- Niccolette Schaunaman
- Department of Medicine, National Jewish Health, 1400 Jackson Street, Room A639, Denver, CO, 80206, USA
| | - Diana Cervantes
- Department of Medicine, National Jewish Health, 1400 Jackson Street, Room A639, Denver, CO, 80206, USA
| | - Taylor Nichols
- Department of Medicine, National Jewish Health, 1400 Jackson Street, Room A639, Denver, CO, 80206, USA
| | - Mari Numata
- Department of Medicine, National Jewish Health, 1400 Jackson Street, Room A639, Denver, CO, 80206, USA
| | | | - Monica Kraft
- Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Hong Wei Chu
- Department of Medicine, National Jewish Health, 1400 Jackson Street, Room A639, Denver, CO, 80206, USA.
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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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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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4
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Shibayama N. Allosteric transitions in hemoglobin revisited. Biochim Biophys Acta Gen Subj 2020; 1864:129335. [DOI: 10.1016/j.bbagen.2019.03.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2018] [Revised: 03/27/2019] [Accepted: 03/30/2019] [Indexed: 12/19/2022]
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5
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Shibayama N, Ohki M, Tame JRH, Park SY. Direct observation of conformational population shifts in crystalline human hemoglobin. J Biol Chem 2017; 292:18258-18269. [PMID: 28931607 DOI: 10.1074/jbc.m117.781146] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 08/15/2017] [Indexed: 11/06/2022] Open
Abstract
Although X-ray crystallography is the most commonly used technique for studying the molecular structure of proteins, it is not generally able to monitor the dynamic changes or global domain motions that often underlie allostery. These motions often prevent crystal growth or reduce crystal order. We have recently discovered a crystal form of human hemoglobin that contains three protein molecules allowed to express a full range of quaternary structures, whereas maintaining strong X-ray diffraction. Here we use this crystal form to investigate the effects of two allosteric effectors, phosphate and bezafibrate, by tracking the structures and functions of the three hemoglobin molecules following the addition of each effector. The X-ray analysis shows that the addition of either phosphate or bezafibrate not only induces conformational changes in a direction from a relaxed-state to a tense-state, but also within relaxed-state populations. The microspectrophotometric O2 equilibrium measurements on the crystals demonstrate that the binding of each effector energetically stabilizes the lowest affinity conformer more strongly than the intermediate affinity one, thereby reducing the O2 affinity of tense-state populations, and that the addition of bezafibrate causes an ∼5-fold decrease in the O2 affinity of relaxed-state populations. These results show that the allosteric pathway of hemoglobin involves shifts of populations rather than a unidirectional conversion of one quaternary structure to another, and that minor conformers of hemoglobin may have a disproportionate effect on the overall O2 affinity.
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Affiliation(s)
- Naoya Shibayama
- From the Department of Physiology, Division of Biophysics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498 and
| | - Mio Ohki
- the Drug Design Laboratory, Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro, Tsurumi, Yokohama 230-0045, Japan
| | - Jeremy R H Tame
- the Drug Design Laboratory, Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro, Tsurumi, Yokohama 230-0045, Japan
| | - Sam-Yong Park
- the Drug Design Laboratory, Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro, Tsurumi, Yokohama 230-0045, Japan
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6
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Shibayama N, Sugiyama K, Tame JRH, Park SY. Capturing the Hemoglobin Allosteric Transition in a Single Crystal Form. J Am Chem Soc 2014; 136:5097-105. [DOI: 10.1021/ja500380e] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Naoya Shibayama
- Division
of Biophysics, Department of Physiology, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan
| | - Kanako Sugiyama
- Drug
Design Laboratory, Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro, Tsurumi, Yokohama, 230-0045, Japan
| | - Jeremy R. H. Tame
- Drug
Design Laboratory, Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro, Tsurumi, Yokohama, 230-0045, Japan
| | - Sam-Yong Park
- Drug
Design Laboratory, Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro, Tsurumi, Yokohama, 230-0045, Japan
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7
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Ren Z. Reverse engineering the cooperative machinery of human hemoglobin. PLoS One 2013; 8:e77363. [PMID: 24312167 PMCID: PMC3842276 DOI: 10.1371/journal.pone.0077363] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 08/30/2013] [Indexed: 11/25/2022] Open
Abstract
Hemoglobin transports molecular oxygen from the lungs to all human tissues for cellular respiration. Its α2β2 tetrameric assembly undergoes cooperative binding and releasing of oxygen for superior efficiency and responsiveness. Over past decades, hundreds of hemoglobin structures were determined under a wide range of conditions for investigation of molecular mechanism of cooperativity. Based on a joint analysis of hemoglobin structures in the Protein Data Bank (Ren, companion article), here I present a reverse engineering approach to elucidate how two subunits within each dimer reciprocate identical motions that achieves intradimer cooperativity, how ligand-induced structural signals from two subunits are integrated to drive quaternary rotation, and how the structural environment at the oxygen binding sites alter their binding affinity. This mechanical model reveals the intricate design that achieves the cooperative mechanism and has previously been masked by inconsistent structural fluctuations. A number of competing theories on hemoglobin cooperativity and broader protein allostery are reconciled and unified.
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Affiliation(s)
- Zhong Ren
- Center for Advanced Radiation Sources, The University of Chicago, Argonne, Illinois, United States of America
- Renz Research, Inc., Westmont, Illinois, United States of America
- * E-mail:
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Reaction trajectory revealed by a joint analysis of protein data bank. PLoS One 2013; 8:e77141. [PMID: 24244274 PMCID: PMC3823880 DOI: 10.1371/journal.pone.0077141] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 08/29/2013] [Indexed: 11/19/2022] Open
Abstract
Structural motions along a reaction pathway hold the secret about how a biological macromolecule functions. If each static structure were considered as a snapshot of the protein molecule in action, a large collection of structures would constitute a multidimensional conformational space of an enormous size. Here I present a joint analysis of hundreds of known structures of human hemoglobin in the Protein Data Bank. By applying singular value decomposition to distance matrices of these structures, I demonstrate that this large collection of structural snapshots, derived under a wide range of experimental conditions, arrange orderly along a reaction pathway. The structural motions along this extensive trajectory, including several helical transformations, arrive at a reverse engineered mechanism of the cooperative machinery (Ren, companion article), and shed light on pathological properties of the abnormal homotetrameric hemoglobins from α-thalassemia. This method of meta-analysis provides a general approach to structural dynamics based on static protein structures in this post genomics era.
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9
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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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Bettati S, Viappiani C, Mozzarelli A. Hemoglobin, an “evergreen” red protein. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2009; 1794:1317-24. [DOI: 10.1016/j.bbapap.2009.03.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Accepted: 03/23/2009] [Indexed: 10/20/2022]
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11
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Ronda L, Abbruzzetti S, Bruno S, Bettati S, Mozzarelli A, Viappiani C. Ligand-Induced Tertiary Relaxations During the T-to-R Quaternary Transition in Hemoglobin. J Phys Chem B 2008; 112:12790-4. [DOI: 10.1021/jp803040j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Luca Ronda
- Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, CNISM, and Dipartimento di Fisica, Università degli Studi di Parma, CNISM, and NEST CNR-INFM
| | - Stefania Abbruzzetti
- Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, CNISM, and Dipartimento di Fisica, Università degli Studi di Parma, CNISM, and NEST CNR-INFM
| | - Stefano Bruno
- Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, CNISM, and Dipartimento di Fisica, Università degli Studi di Parma, CNISM, and NEST CNR-INFM
| | - Stefano Bettati
- Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, CNISM, and Dipartimento di Fisica, Università degli Studi di Parma, CNISM, and NEST CNR-INFM
| | - Andrea Mozzarelli
- Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, CNISM, and Dipartimento di Fisica, Università degli Studi di Parma, CNISM, and NEST CNR-INFM
| | - Cristiano Viappiani
- Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, CNISM, and Dipartimento di Fisica, Università degli Studi di Parma, CNISM, and NEST CNR-INFM
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13
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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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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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Yun KM, Morimoto H, Shibayama N. The contribution of the asymmetric alpha 1beta 1 half-oxygenated intermediate to human hemoglobin cooperativity. J Biol Chem 2002; 277:1878-83. [PMID: 11714709 DOI: 10.1074/jbc.m108494200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Considerable controversy remains as to the functional and structural properties of the asymmetric alpha1beta1 half-oxygenated intermediate of human hemoglobin, consisting of a deoxygenated and an oxygenated dimer. A recent dimer-tetramer equilibrium study using [Zn(II)/Fe(II)-O(2)] hybrid hemoglobins, in which Zn-protoporphyrin IX mimics a deoxyheme, showed that the key intermediate, [alpha(Fe-O(2))beta(Fe-O(2))][alpha(Zn)beta(Zn)], exhibited an enhanced tetramer stability relative to the other doubly oxygenated species. This is one of the strongest findings in support of distinctly favorable intra-dimer cooperativity within the tetramer. However, we present here a different conclusion drawn from direct O(2) binding experiments for the same asymmetric hybrid, [alpha(Fe)beta(Fe)][alpha(Zn)beta(Zn)], and those for [alpha(Fe)beta(Zn)](2) and [alpha(Zn)beta(Fe)](2). In this study, the O(2) equilibrium curves for [alpha(Fe)beta(Fe)][alpha(Zn)beta(Zn)] were determined by an O(2)-jump stopped-flow technique to circumvent the problem of dimer rearrangement, and those for [alpha(Fe)beta(Zn)]( 2) and [alpha(Zn)beta(Fe)]( 2) were measured by using an Imai apparatus. It was shown that the first and second O(2) equilibrium constants for [alpha(Fe)beta(Fe)][alpha(Zn)beta(Zn)] are 0.0209 mmHg(-1) and 0.0276 mmHg(-1), respectively, that are almost identical to those for [alpha(Fe)beta(Zn)](2) or [alpha(Zn)beta(Fe)](2). Therefore, we did not observe large difference among the asymmetric and symmetric hybrids. The discrepancy between the present and previous studies is mainly due to previously observed negative cooperativity for [alpha(Fe)beta(Zn)](2) and [alpha(Zn)beta(Fe)](2), which is not the case in our direct O(2) binding study.
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Affiliation(s)
- Kyung-Mook Yun
- Department of Physics, Jichi Medical School, Yakushiji 3311-1, Minamikawachi, Kawachi, Tochigi 329-0498, Japan
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16
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Shibayama N. Functional analysis of hemoglobin molecules locked in doubly liganded conformations. J Mol Biol 1999; 285:1383-8. [PMID: 9917383 DOI: 10.1006/jmbi.1998.2407] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A controversy still exists over whether the molecular basis of hemoglobin cooperativity can be more appropriately explained by one of two classic allosteric models, the concerted and sequential models. To distinguish these two models from the viewpoint of their fundamental processes, namely, the presence or absence of conformational equilibria, we have trapped the conformations of nickel(II)-iron(II) hybrid hemoglobin molecules with two CO-bound, alpha2(Fe-CO)beta2(Ni) and alpha2(Ni)beta2(Fe-CO), by encapsulation in the water-filled pores of sol-gel-derived transparent silica-gels. In our experimental system, nickel(II) protoporphyrin binds neither O2 nor CO and mimics a fixed deoxyheme, and the gel matrix provides a means of inhibiting large-scale protein structural changes, thus enabling O2 equilibrium study of the hybrids still in their doubly liganded conformations. Results showed that two conformations of widely different O2 affinity exist together in each doubly liganded hemoglobin, providing a direct proof of the concerted mechanism versus the sequential mechanism.
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Affiliation(s)
- N Shibayama
- Department of Physics, Jichi Medical School, Yakushiji 3311-1 Minamikawachi, Kawachi, Tochigi, 329-0498, Japan.
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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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Perutz MF, Wilkinson AJ, Paoli M, Dodson GG. The stereochemical mechanism of the cooperative effects in hemoglobin revisited. ANNUAL REVIEW OF BIOPHYSICS AND BIOMOLECULAR STRUCTURE 1998; 27:1-34. [PMID: 9646860 DOI: 10.1146/annurev.biophys.27.1.1] [Citation(s) in RCA: 399] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In 1970, Perutz tried to put the allosteric mechanism of hemoglobin, proposed by Monod, Wyman and Changeux in 1965, on a stereochemical basis. He interpreted their two-state model in terms of an equilibrium between two alternative structures, a tense one (T) with low oxygen affinity, constrained by salt-bridges between the C-termini of the four subunits, and a relaxed one (R) lacking these bridges. The equilibrium was thought to be governed primarily by the positions of the iron atoms relative to the porphyrin: out-of-plane in five-coordinated, high-spin deoxyhemoglobin, and in-plane in six-coordinated, low-spin oxyhemoglobin. The tension exercised by the salt-bridges in the T-structure was to be transmitted to the heme-linked histidines and to restrain the movement of the iron atoms into the porphyrin plane that is necessary for oxygen binding. At the beta-hemes, the distal valine and histidine block the oxygen-combining site in the T-structure; its tension was thought to strengthen that blockage. Finally, Perutz attributed the linearity of proton release with early oxygen uptake to the sequential rupture of salt-bridges in the T-structure and to the accompanying drop in pKa of the weak bases that form part of them. Almost every feature of this mechanism has been disputed, but evidence that has come to light more than 25 years later now shows it to have been substantially correct. That new evidence is reviewed below.
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Affiliation(s)
- M F Perutz
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
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Ackers GK. Deciphering the molecular code of hemoglobin allostery. ADVANCES IN PROTEIN CHEMISTRY 1998; 51:185-253. [PMID: 9615171 DOI: 10.1016/s0065-3233(08)60653-1] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- G K Ackers
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Bettati S, Mozzarelli A. T state hemoglobin binds oxygen noncooperatively with allosteric effects of protons, inositol hexaphosphate, and chloride. J Biol Chem 1997; 272:32050-5. [PMID: 9405399 DOI: 10.1074/jbc.272.51.32050] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Hemoglobin is the paradigm of allosteric proteins. Over the years, cooperative oxygen binding has been explained by different models predicting that the T state of hemoglobin binds oxygen either noncooperatively or with some degree of cooperativity or with strong cooperativity. Therefore, a critical test that discriminates among models is to determine the oxygen binding by the T state of hemoglobin. Fixation of hemoglobin in the T state has been achieved either by crystallization from polyethylene glycol solutions or by encapsulation in wet porous silica gels. Hemoglobin crystals bind oxygen noncooperatively with reduced affinity compared with solution, with no Bohr effect and with no influence of other allosteric effectors. In this study, we have determined accurate oxygen-binding curves to the T state of hemoglobin in silica gels with the same microspectrophotometric apparatus and multiwavelengths analysis used in crystal experiments. The T state of hemoglobin in silica gels binds oxygen noncooperatively with an affinity and a Bohr effect similar to those observed in solution for the binding of the first oxygen molecule. Other allosteric effectors such as inositol hexaphosphate, bezafibrate, and chloride significantly affect oxygen affinity. Therefore, T state hemoglobins that are characterized by strikingly different functional properties share the absence of cooperativity in the binding of oxygen. These findings are fully consistent with the Monod, Wyman, and Changeux model and with most features of Perutz's stereochemical model, but they are not consistent with models of both Koshland and Ackers.
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Affiliation(s)
- S Bettati
- Institute of Biochemical Sciences, University of Parma, 43100 Parma, Italy
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Huang Y, Doyle ML, Ackers GK. The oxygen-binding intermediates of human hemoglobin: evaluation of their contributions to cooperativity using zinc-containing hybrids. Biophys J 1996; 71:2094-105. [PMID: 8889184 PMCID: PMC1233676 DOI: 10.1016/s0006-3495(96)79408-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Hemoglobin tetramers [Zn/FeO(2)] containing oxygenated subunits (FeO(2)), in combination with unligated subunits containing zinc-substituted hemes (Zn), were analyzed to determine their contributions to the cooperativity of oxygen binding at the Fe sites. Energetic consequences of possible perturbation by zinc substitution were evaluated in all combinations of unligated Zn/Fe hybrid tetramers. A general thermodynamic strategy that corrects for the energetic effects of substituting a second metal for Fe showed the perturbations of Zn substitution to be negligible. This permitted cooperativity parameters of the native Fe/FeO(2) intermediates to be calculated from data on the corresponding Zn/FeO(2) molecules. These parameters, determined explicitly for all eight oxygen-binding intermediates (Fe/FeO(2)), were found to be identical to those predicted earlier from analyzing the O(2) binding data of normal hemoglobin according to the "molecular code" of hemoglobin allostery. The cooperativity parameters determined for this system showed the same distribution pattern found previously for five other oxygen analog systems (Fe/FeCN, FE/Mn(3+), Co/FECO, Co/FeCN, and Fe/FeCO).
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Affiliation(s)
- Y Huang
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Bettati S, Mozzarelli A, Rossi GL, Tsuneshige A, Yonetani T, Eaton WA, Henry ER. Oxygen binding by single crystals of hemoglobin: The problem of cooperativity and inequivalence of alpha and beta subunits. Proteins 1996. [DOI: 10.1002/(sici)1097-0134(199608)25:4<425::aid-prot3>3.0.co;2-c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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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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