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Critical Role of Hemopexin Mediated Cytoprotection in the Pathophysiology of Sickle Cell Disease. Int J Mol Sci 2021; 22:ijms22126408. [PMID: 34203861 PMCID: PMC8232622 DOI: 10.3390/ijms22126408] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 06/09/2021] [Accepted: 06/13/2021] [Indexed: 02/07/2023] Open
Abstract
Circulating hemopexin is the primary protein responsible for the clearance of heme; therefore, it is a systemic combatant against deleterious inflammation and oxidative stress induced by the presence of free heme. This role of hemopexin is critical in hemolytic pathophysiology. In this review, we outline the current research regarding how the dynamic activity of hemopexin is implicated in sickle cell disease, which is characterized by a pathological aggregation of red blood cells and excessive hemolysis. This pathophysiology leads to symptoms such as acute kidney injury, vaso-occlusion, ischemic stroke, pain crises, and pulmonary hypertension exacerbated by the presence of free heme and hemoglobin. This review includes in vivo studies in mouse, rat, and guinea pig models of sickle cell disease, as well as studies in human samples. In summary, the current research indicates that hemopexin is likely protective against these symptoms and that rectifying depleted hemopexin in patients with sickle cell disease could improve or prevent the symptoms. The data compiled in this review suggest that further preclinical and clinical research should be conducted to uncover pathways of hemopexin in pathological states to evaluate its potential clinical function as both a biomarker and therapy for sickle cell disease and related hemoglobinopathies.
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2
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Detzel MS, Schmalohr BF, Steinbock F, Hopp MT, Ramoji A, Paul George AA, Neugebauer U, Imhof D. Revisiting the interaction of heme with hemopexin. Biol Chem 2021; 402:675-691. [PMID: 33581700 DOI: 10.1515/hsz-2020-0347] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 02/06/2021] [Indexed: 12/23/2022]
Abstract
In hemolytic disorders, erythrocyte lysis results in massive release of hemoglobin and, subsequently, toxic heme. Hemopexin is the major protective factor against heme toxicity in human blood and currently considered for therapeutic use. It has been widely accepted that hemopexin binds heme with extraordinarily high affinity of <1 pM in a 1:1 ratio. However, several lines of evidence point to a higher stoichiometry and lower affinity than determined 50 years ago. Here, we re-analyzed these data. SPR and UV/Vis spectroscopy were used to monitor the interaction of heme with the human protein. The heme-binding sites of hemopexin were characterized using hemopexin-derived peptide models and competitive displacement assays. We obtained a K D value of 0.32 ± 0.04 nM and the ratio for the interaction was determined to be 1:1 at low heme concentrations and at least 2:1 (heme:hemopexin) at high concentrations. We were able to identify two yet unknown potential heme-binding sites on hemopexin. Furthermore, molecular modelling with a newly created homology model of human hemopexin suggested a possible recruiting mechanism by which heme could consecutively bind several histidine residues on its way into the binding pocket. Our findings have direct implications for the potential administration of hemopexin in hemolytic disorders.
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Affiliation(s)
- Milena Sophie Detzel
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, An der Immenburg 4, D-53121Bonn, Germany
| | - Benjamin Franz Schmalohr
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, An der Immenburg 4, D-53121Bonn, Germany
| | - Francèl Steinbock
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, An der Immenburg 4, D-53121Bonn, Germany
| | - Marie-Thérèse Hopp
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, An der Immenburg 4, D-53121Bonn, Germany
| | - Anuradha Ramoji
- Center for Sepsis Control and Care (CSCC), Jena University Hospital, D-07747Jena, Germany.,Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, D-07745Jena, Germany
| | - Ajay Abisheck Paul George
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, An der Immenburg 4, D-53121Bonn, Germany
| | - Ute Neugebauer
- Center for Sepsis Control and Care (CSCC), Jena University Hospital, D-07747Jena, Germany.,Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, D-07745Jena, Germany
| | - Diana Imhof
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, An der Immenburg 4, D-53121Bonn, Germany
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3
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Karnaukhova E, Owczarek C, Schmidt P, Schaer DJ, Buehler PW. Human Plasma and Recombinant Hemopexins: Heme Binding Revisited. Int J Mol Sci 2021; 22:ijms22031199. [PMID: 33530421 PMCID: PMC7866118 DOI: 10.3390/ijms22031199] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 12/24/2020] [Indexed: 11/24/2022] Open
Abstract
Plasma hemopexin (HPX) is the key antioxidant protein of the endogenous clearance pathway that limits the deleterious effects of heme released from hemoglobin and myoglobin (the term “heme” is used in this article to denote both the ferrous and ferric forms). During intra-vascular hemolysis, heme partitioning to protein and lipid increases as the plasma concentration of HPX declines. Therefore, the development of HPX as a replacement therapy during high heme stress could be a relevant intervention for hemolytic disorders. A logical approach to enhance HPX yield involves recombinant production strategies from human cell lines. The present study focuses on a biophysical assessment of heme binding to recombinant human HPX (rhHPX) produced in the Expi293FTM (HEK293) cell system. In this report, we examine rhHPX in comparison with plasma HPX using a systematic analysis of protein structural and functional characteristics related to heme binding. Analysis of rhHPX by UV/Vis absorption spectroscopy, circular dichroism (CD), size-exclusion chromatography (SEC)-HPLC, and catalase-like activity demonstrated a similarity to HPX fractionated from plasma. In particular, the titration of HPX apo-protein(s) with heme was performed for the first time using a wide range of heme concentrations to model HPX–heme interactions to approximate physiological conditions (from extremely low to more than two-fold heme molar excess over the protein). The CD titration data showed an induced bisignate CD Soret band pattern typical for plasma and rhHPX versions at low heme-to-protein molar ratios and demonstrated that further titration is dependent on the amount of protein-bound heme to the extent that the arising opposite CD couplet results in a complete inversion of the observed CD pattern. The data generated in this study suggest more than one binding site in both plasma and rhHPX. Furthermore, our study provides a useful analytical platform for the detailed characterization of HPX–heme interactions and potentially novel HPX fusion constructs.
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Affiliation(s)
- Elena Karnaukhova
- Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD 20993, USA
- Correspondence: (E.K.); (P.W.B.)
| | - Catherine Owczarek
- CSL Limited, Bio21 Institute, Parkville, Victoria 3010, Australia; (C.O.); (P.S.)
| | - Peter Schmidt
- CSL Limited, Bio21 Institute, Parkville, Victoria 3010, Australia; (C.O.); (P.S.)
| | - Dominik J. Schaer
- Division of Internal Medicine, University Hospital of Zurich, 8091 Zurich, Switzerland;
| | - Paul W. Buehler
- Department of Pathology, The University of Maryland School of Medicine, Baltimore, MD 21201, USA
- The Center for Blood Oxygen Transport and Hemostasis, Department of Pediatrics, The University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Correspondence: (E.K.); (P.W.B.)
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4
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Girr P, Kilper J, Pohland AC, Paulsen H. The pigment binding behaviour of water-soluble chlorophyll protein (WSCP). Photochem Photobiol Sci 2020; 19:695-712. [PMID: 32338263 DOI: 10.1039/d0pp00043d] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Accepted: 04/17/2020] [Indexed: 12/17/2023]
Abstract
Water-soluble chlorophyll proteins (WSCPs) are homotetrameric proteins that bind four chlorophyll (Chl) molecules in identical binding sites, which makes WSCPs a good model to study protein-pigment interactions. In a previous study, we described preferential binding of Chl a or Chl b in various WSCP versions. Chl b binding is preferred when a hydrogen bond can be formed between the C7 formyl of the chlorin macrocycle and the protein, whereas Chl a is preferred when Chl b binding is sterically unfavorable. Here, we determined the binding affinities and kinetics of various WSCP versions not only for Chl a/b, but also for chlorophyllide (Chlide) a/b and pheophytin (Pheo) a/b. Altered KD values are responsible for the Chl a/b selectivity in WSCP whereas differences in the reaction kinetics are neglectable in explaining different Chl a/b preferences. WSCP binds both Chlide and Pheo with a lower affinity than Chl, which indicates the importance of the phytol chain and the central Mg2+ ion as interaction sites between WSCP and pigment. Pheophorbide (Pheoide), lacking both the phytol chain and the central Mg2+ ion, can only be bound as Pheoide b to a WSCP that has a higher affinity for Chl b than Chl a, which underlines the impact of the C7 formyl-protein interaction. Moreover, WSCP was able to bind protochlorophyllide and Mg-protoporphyrin IX, which suggests that neither the size of the π electron system of the macrocycle nor the presence of a fifth ring at the macrocycle notably affect the binding to WSCP. WSCP also binds heme to form a tetrameric complex, suggesting that heme is bound in the Chl-binding site.
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Affiliation(s)
- Philipp Girr
- Institute of Molecular Physiology, Johannes Gutenberg-University Mainz, Johannes-von-Müller-Weg 6, 55128, Mainz, Germany
| | - Jessica Kilper
- Institute of Molecular Physiology, Johannes Gutenberg-University Mainz, Johannes-von-Müller-Weg 6, 55128, Mainz, Germany
| | - Anne-Christin Pohland
- Institute of Molecular Physiology, Johannes Gutenberg-University Mainz, Johannes-von-Müller-Weg 6, 55128, Mainz, Germany
| | - Harald Paulsen
- Institute of Molecular Physiology, Johannes Gutenberg-University Mainz, Johannes-von-Müller-Weg 6, 55128, Mainz, Germany.
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Nguyen TPH, Patrick CJ, Parry LJ, Familari M. Using proteomics to advance the search for potential biomarkers for preeclampsia: A systematic review and meta-analysis. PLoS One 2019; 14:e0214671. [PMID: 30951540 PMCID: PMC6450632 DOI: 10.1371/journal.pone.0214671] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 03/18/2019] [Indexed: 02/01/2023] Open
Abstract
BACKGROUND Preeclampsia (PE) is a leading cause of maternal and perinatal morbidity and mortality worldwide. Although predictive multiparametric screening is being developed, it is not applicable to nulliparous women, and is not applied to low-risk women. As PE is considered a heterogenous disorder, it is unlikely that any single multiparametric screening protocol containing a small group of biomarkers could have the required accuracy to predict all PE subgroups. Given the etiology of PE is complex and not fully understood, it begs the question, whether the search for biomarkers based on the predominant view of impaired placentation involving factors predominately implicated in angiogenesis and inflammation, has been too limiting. Here we highlight the enormous potential of state-of-the-art, high-throughput proteomics, to provide a comprehensive and unbiased approach to biomarker identification. METHODS AND FINDINGS Our literature search identified 1336 articles; after review, 45 studies with proteomic data from PE women that were eligible for inclusion. From 710 proteins with altered abundance, we identified 13 common circulating proteins, some of which had not been previously considered as prospective biomarkers of PE. An additional search of the literature for original publications testing any of the 13 common proteins using non-proteomic techniques was also undertaken. Strikingly, 9 of these common proteins had been independently evaluated in PE studies as potential biomarkers. CONCLUSION This study highlights the potential of using high-throughput data sets, which are comprehensive and without bias, to identify a profile of proteins that may improve predictions of PE and understanding of its etiology. We bring to the attention of the medical and research communities that the strengths and advantages of using data from high-throughput studies for biomarker discovery would be increased dramatically, if first and second trimester samples were collected for proteomics, and if standardized guidelines for patient reporting and data collection were implemented.
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Affiliation(s)
| | | | - Laura Jean Parry
- School of BioSciences, University of Melbourne, Parkville, Australia
| | - Mary Familari
- School of BioSciences, University of Melbourne, Parkville, Australia
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6
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Hahl P, Hunt R, Bjes ES, Skaff A, Keightley A, Smith A. Identification of oxidative modifications of hemopexin and their predicted physiological relevance. J Biol Chem 2017; 292:13658-13671. [PMID: 28596380 DOI: 10.1074/jbc.m117.783951] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 06/07/2017] [Indexed: 12/26/2022] Open
Abstract
Hemopexin protects against heme toxicity in hemolytic diseases and conditions, sepsis, and sickle cell disease. This protection is sustained by heme-hemopexin complexes in biological fluids that resist oxidative damage during heme-driven inflammation. However, apo-hemopexin is vulnerable to inactivation by reactive nitrogen (RNS) and oxygen species (ROS) that covalently modify amino acids. The resultant nitration of amino acids is considered a specific effect reflecting biological events. Using LC-MS, we discovered low endogenous levels of tyrosine nitration in the peptide YYCFQGNQFLR in the heme-binding site of human hemopexin, which was similarly nitrated in rabbit and rat hemopexins. Immunoblotting and selective reaction monitoring were used to quantify tyrosine nitration of in vivo samples and when hemopexin was incubated in vitro with nitrating nitrite/myeloperoxidase/glucose oxidase. Significantly, heme binding by hemopexin declined as tyrosine nitration proceeded in vitro Three nitrated tyrosines reside in the heme-binding site of hemopexin, and we found that one, Tyr-199, interacts directly with the heme ring D propionate. Investigating the oxidative modifications of amino acids after incubation with tert-butyl hydroperoxide and hypochlorous acid in vitro, we identified additional covalent oxidative modifications on four tyrosine residues and one tryptophan residue of hemopexin. Importantly, three of the four modified tyrosines, some of which have more than one modification, cluster in the heme-binding site, supporting a hierarchy of vulnerable amino acids. We propose that during inflammation, apo-hemopexin is nitrated and oxidated in niches of the body containing activated RNS- and ROS-generating immune and endothelial cells, potentially impairing hemopexin's protective extracellular antioxidant function.
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Affiliation(s)
- Peter Hahl
- From the Department of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri 64110-2239
| | - Rachel Hunt
- From the Department of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri 64110-2239
| | - Edward S Bjes
- From the Department of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri 64110-2239
| | - Andrew Skaff
- From the Department of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri 64110-2239
| | - Andrew Keightley
- From the Department of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri 64110-2239
| | - Ann Smith
- From the Department of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri 64110-2239
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7
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Mohan S, Narumiya S, Doré S. Neuroprotective role of prostaglandin PGE2 EP2 receptor in hemin-mediated toxicity. Neurotoxicology 2015; 46:53-9. [PMID: 25451967 PMCID: PMC4681391 DOI: 10.1016/j.neuro.2014.10.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 10/18/2014] [Accepted: 10/23/2014] [Indexed: 01/01/2023]
Abstract
Heme (Fe(2+) protoporphyrin IX) and hemin (Fe(3+)), the prosthetic group of hemoprotein, are cytotoxic due to their ability to contribute to the production of reactive oxygen species, increased intracellular calcium levels, and stimulate glutamate-mediated excitotoxicity. Previous work by our group showed that blockade of the prostaglandin E2 (PGE2)-EP1 receptor reduced hemin-induced cytotoxicity in primary cortical neuronal cultures. However, the role of the prostaglandin E2 (PGE2)-EP2 receptor in hemin neurotoxicity remains unclear. Activation of the EP2 receptor in neurons results in increased cyclic AMP (cAMP) and protein kinase A signaling; therefore, we hypothesized that the activation of the EP2 receptor decreases hemin neurotoxicity. Using postnatal primary cortical neurons cultured from wildtype-control (WT) and EP2(-/-) mice, we investigated the role of the EP2 receptor in hemin neurotoxicity by monitoring cell survival with the Calcein-AM live-cell and lactate dehydrogenase assays. MitoTracker staining was also performed to determine how mitochondria were affected by hemin. Hemin neurotoxicity in EP2(-/-) neurons was 37.2 ± 17.0% greater compared to WT neurons. Of interest, cotreatment with the EP2 receptor agonist, butaprost (1 and 10 μM), significantly attenuated hemin neurotoxicity by 55.7 ± 21.1% and 60.1 ± 14.8%, respectively. To further investigate signaling mechanisms related to EP2 receptor mediating cytoprotection, neurons were cotreated with hemin and activators/inhibitors of both the cAMP-protein kinase A/exchange protein directly activated by cAMP (Epac) pathways. Forskolin, a cAMP activator, and 8-pCPT-cAMP, an Epac activator, both attenuated hemin neurotoxicity by 78.8 ± 22.2% and 58.4 ± 9.8%, respectively, as measured using the lactate dehydrogenase assay. Together, the results reveal that activation of the EP2 receptor is protective against hemin neurotoxicity in vitro and these findings suggest that neuroprotection occurs through the cAMP-Epac pathway in neuronal cultures. Therefore, activation of the EP2 receptor could be used to minimize neuronal damage following exposure to supraphysiological levels of hemin.
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MESH Headings
- Adjuvants, Immunologic/pharmacology
- Alprostadil/analogs & derivatives
- Alprostadil/pharmacology
- Analysis of Variance
- Animals
- Animals, Newborn
- Cell Survival/drug effects
- Cerebral Cortex/cytology
- Colforsin/pharmacology
- Cyclic AMP/analogs & derivatives
- Cyclic AMP/pharmacology
- Dose-Response Relationship, Drug
- Excitatory Amino Acid Agonists/pharmacology
- Glutamic Acid/pharmacology
- Hemin/toxicity
- L-Lactate Dehydrogenase/metabolism
- Mice
- Mice, Knockout
- Neurons/drug effects
- Neuroprotective Agents/pharmacology
- Receptors, Prostaglandin E, EP2 Subtype/agonists
- Receptors, Prostaglandin E, EP2 Subtype/genetics
- Receptors, Prostaglandin E, EP2 Subtype/metabolism
- Thionucleotides/pharmacology
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Affiliation(s)
- Shekher Mohan
- Department of Anesthesiology, University of Florida, Gainesville, FL, USA
| | - Shuh Narumiya
- Department of Pharmacology, Kyoto University, Kyoto, Japan
| | - Sylvain Doré
- Department of Anesthesiology, University of Florida, Gainesville, FL, USA; Departments of Neurology, Psychiatry, and Neuroscience, University of Florida, Gainesville, FL, USA.
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8
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Abstract
Heme, which is composed of iron and the small organic molecule protoporphyrin, is an essential component of hemoglobin as well as a variety of physiologically important hemoproteins. During erythropoiesis, heme synthesis is induced before, and is essential for, globin synthesis. Although all cells possess the ability to synthesize heme, there are distinct differences between regulation of the pathway in developing erythroid cells and all other types of cells. Disorders that compromise the ability of the developing red cell to synthesize heme can have profound medical implications. The biosynthetic pathway for heme and key regulatory features are reviewed herein, along with specific human genetic disorders that arise from defective heme synthesis such as X-linked sideroblastic anemia and erythropoietic protoporphyria.
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Affiliation(s)
- Harry A Dailey
- Department of Microbiology, Department of Biochemistry and Molecular Biology, Biomedical and Health Sciences Institute, University of Georgia, Athens, GA 30602, USA.
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9
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Hamza I, Dailey HA. One ring to rule them all: trafficking of heme and heme synthesis intermediates in the metazoans. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:1617-32. [PMID: 22575458 DOI: 10.1016/j.bbamcr.2012.04.009] [Citation(s) in RCA: 163] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 04/15/2012] [Accepted: 04/19/2012] [Indexed: 12/17/2022]
Abstract
The appearance of heme, an organic ring surrounding an iron atom, in evolution forever changed the efficiency with which organisms were able to generate energy, utilize gasses and catalyze numerous reactions. Because of this, heme has become a near ubiquitous compound among living organisms. In this review we have attempted to assess the current state of heme synthesis and trafficking with a goal of identifying crucial missing information, and propose hypotheses related to trafficking that may generate discussion and research. The possibilities of spatially organized supramolecular enzyme complexes and organelle structures that facilitate efficient heme synthesis and subsequent trafficking are discussed and evaluated. Recently identified players in heme transport and trafficking are reviewed and placed in an organismal context. Additionally, older, well established data are reexamined in light of more recent studies on cellular organization and data available from newer model organisms. This article is part of a Special Issue entitled: Cell Biology of Metals.
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Affiliation(s)
- Iqbal Hamza
- Department of Animal & Avian Sciences, University of Maryland, College Park, MD 20742, USA.
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10
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Higdon AN, Benavides GA, Chacko BK, Ouyang X, Johnson MS, Landar A, Zhang J, Darley-Usmar VM. Hemin causes mitochondrial dysfunction in endothelial cells through promoting lipid peroxidation: the protective role of autophagy. Am J Physiol Heart Circ Physiol 2012; 302:H1394-409. [PMID: 22245770 DOI: 10.1152/ajpheart.00584.2011] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The hemolysis of red blood cells and muscle damage results in the release of the heme proteins myoglobin, hemoglobin, and free heme into the vasculature. The mechanisms of heme toxicity are not clear but may involve lipid peroxidation, which we hypothesized would result in mitochondrial damage in endothelial cells. To test this, we used bovine aortic endothelial cells (BAEC) in culture and exposed them to hemin. Hemin led to mitochondrial dysfunction, activation of autophagy, mitophagy, and, at high concentrations, apoptosis. To detect whether hemin induced lipid peroxidation and damaged proteins, we used derivatives of arachidonic acid tagged with biotin or Bodipy (Bt-AA, BD-AA). We found that in cells treated with hemin, Bt-AA was oxidized and formed adducts with proteins, which were inhibited by α-tocopherol. Hemin-dependent mitochondrial dysfunction was also attenuated by α-tocopherol. Protein thiol modification and carbonyl formation occurred on exposure and was not inhibited by α-tocopherol. Supporting a protective role of autophagy, the inhibitor 3-methyladenine potentiated cell death. These data demonstrate that hemin mediates cytotoxicity through a mechanism which involves protein modification by oxidized lipids and other oxidants, decreased respiratory capacity, and a protective role for the autophagic process. Attenuation of lipid peroxidation may be able to preserve mitochondrial function in the endothelium and protect cells from heme-dependent toxicity.
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Affiliation(s)
- Ashlee N Higdon
- Department of Pathology, Center For Free Radical Biology, University of Alabama at Birmingham, USA
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11
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Kühl T, Sahoo N, Nikolajski M, Schlott B, Heinemann SH, Imhof D. Determination of hemin-binding characteristics of proteins by a combinatorial peptide library approach. Chembiochem 2011; 12:2846-55. [PMID: 22045633 DOI: 10.1002/cbic.201100556] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Indexed: 12/28/2022]
Abstract
Studies of the binding of heme/hemin to proteins or peptides have recently intensified as it became evident that heme serves not only as a prosthetic group, but also as a regulator and effector molecule interacting with transmembrane and cytoplasmic proteins. The iron-ion-containing heme group can associate with these proteins in different ways, with the amino acids Cys, His, and Tyr allowing individual modes of binding. Strong coordinate-covalent binding, such as in cytochrome c, is known, and reversible attachment is also discussed. Ligands for both types of binding have been reported independently, though sometimes with different affinities for similar sequences. We applied a combinatorial approach using the library (X)(4) (C/H/Y)(X)(4) to characterize peptide ligands with considerable hemin binding capacities. Some of the library-selected peptides were comparable in terms of hemin association independently of whether or not a cysteine residue was present in the sequence. Indeed, a preference for His-based (≈39 %) and Tyr-based (≈40 %) sequences over Cys-based ones (≈21 %) was detected. The binding affinities for the library-selected peptides, as determined by UV/Vis spectroscopy, were in the nanomolar range. Moreover, selected representatives efficiently competed for hemin binding with the human BK channel hSlo1, which is known to be regulated by heme through binding to its heme-binding domain.
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Affiliation(s)
- Toni Kühl
- Department of Biochemistry and Biophysics, Friedrich Schiller University of Jena, Hans-Knöll-Strasse 2, 07745 Jena, Germany
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12
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Lukat-Rodgers GS, Correia C, Botuyan MV, Mer G, Rodgers KR. Heme-based sensing by the mammalian circadian protein CLOCK. Inorg Chem 2010; 49:6349-65. [PMID: 20666392 DOI: 10.1021/ic902388q] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Heme is emerging as a key player in the synchrony of circadian-coupled transcriptional regulation. Current evidence suggests that levels of circadian-linked transcription are regulated in response to both the availability of intracellular heme and heme-based sensing of carbon monoxide (CO) and possibly nitric oxide (NO). The protein CLOCK is central to the regulation and maintenance of circadian rhythms in mammals. CLOCK comprises two PAS domains, each with a heme binding site. Our studies focus on the functionality of the murine CLOCK PAS-A domain (residues 103-265). We show that CLOCK PAS-A binds iron(III) protoporhyrin IX to form a complex with 1:1 stoichiometry. Optical absorbance and resonance Raman studies reveal that the heme of ferric CLOCK PAS-A is a six-coordinate, low-spin complex whose resonance Raman signature is insensitive to pH over the range of protein stability. Ferrous CLOCK PAS-A is a mixture of five-coordinate, high-spin and six-coordinate, low-spin complexes. Ferrous CLOCK PAS-A forms complexes with CO and NO. Ferric CLOCK PAS-A undergoes reductive nitrosylation in the presence of NO to generate a CLOCK PAS-A-NO, which is a five-coordinate {FeNO}(7) complex. Formation of the highly stable {FeNO}(7) heme complex from either ferrous or ferric heme makes possible the binding of NO at very low concentration, a characteristic of NO sensors. Comparison of the spectroscopic properties and CO-binding kinetics of CLOCK PAS-A with other CO sensor proteins reveals that CLOCK PAS-A exhibits chemical properties consistent with a heme-based gas sensor protein.
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Affiliation(s)
- Gudrun S Lukat-Rodgers
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102, USA
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13
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Krepkova LV, Bortnikova VV, Dzhavakhyan MA, Sokol’skaya TA. Toxicological characterization of new medicinal forms of hiporamin (gel and liniment). Pharm Chem J 2009. [DOI: 10.1007/s11094-009-0290-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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14
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Geurts N, Martens E, Van Aelst I, Proost P, Opdenakker G, Van den Steen PE. β-Hematin Interaction with the Hemopexin Domain of Gelatinase B/MMP-9 Provokes Autocatalytic Processing of the Propeptide, Thereby Priming Activation by MMP-3. Biochemistry 2008; 47:2689-99. [DOI: 10.1021/bi702260q] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Nathalie Geurts
- Laboratory of Immunobiology and Laboratory of Molecular Immunology, Rega Institute for Medical Research, Catholic University of Leuven, Minderbroedersstraat 10, 3000 Leuven, Belgium
| | - Erik Martens
- Laboratory of Immunobiology and Laboratory of Molecular Immunology, Rega Institute for Medical Research, Catholic University of Leuven, Minderbroedersstraat 10, 3000 Leuven, Belgium
| | - Ilse Van Aelst
- Laboratory of Immunobiology and Laboratory of Molecular Immunology, Rega Institute for Medical Research, Catholic University of Leuven, Minderbroedersstraat 10, 3000 Leuven, Belgium
| | - Paul Proost
- Laboratory of Immunobiology and Laboratory of Molecular Immunology, Rega Institute for Medical Research, Catholic University of Leuven, Minderbroedersstraat 10, 3000 Leuven, Belgium
| | - Ghislain Opdenakker
- Laboratory of Immunobiology and Laboratory of Molecular Immunology, Rega Institute for Medical Research, Catholic University of Leuven, Minderbroedersstraat 10, 3000 Leuven, Belgium
| | - Philippe E. Van den Steen
- Laboratory of Immunobiology and Laboratory of Molecular Immunology, Rega Institute for Medical Research, Catholic University of Leuven, Minderbroedersstraat 10, 3000 Leuven, Belgium
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15
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Mauk MR, Rosell FI, Mauk AG. Chromatographically distinguishable heme insertion isoforms of human hemopexin. Biochemistry 2007; 46:15033-41. [PMID: 18044975 DOI: 10.1021/bi701821a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two spectroscopically distinct, non-interconverting forms of human hemopexin have been isolated by immobilized metal ion affinity chromatography and characterized spectroscopically. Form alpha (characterized by a bisignate Soret CD spectrum) and form beta (Soret CD characterized by a positive Cotton effect) exhibit different spectroscopic responses to addition of Zn2+ or Cu2+, yet both forms exhibit the same metal ion-induced decrease in Tm for the thermally induced release of the heme prosthetic group. Far UV-CD spectra indicate that the two isoforms possess essentially identical secondary structures, but their differential retention during metal ion affinity chromatography indicates slight differences in exposure of His residues on the protein surface. We propose that these observations result from the binding of heme in form beta with an orientation that differs from the crystallographically observed binding orientation for rabbit hemopexin by rotation of the heme prosthetic group by 180 degrees about the alpha-gamma meso-carbon axis and from interaction of metal ions at two separate binding sites.
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Affiliation(s)
- Marcia R Mauk
- Department of Biochemistry and Molecular Biology and the Centre for Blood Research, Life Sciences Centre, 2350 Health Sciences Mall, University of British Columbia, Vancouver, BC V6T 1Z3 Canada
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Ascenzi P, Bocedi A, Antonini G, Bolognesi M, Fasano M. Reductive nitrosylation and peroxynitrite-mediated oxidation of heme-hemopexin. FEBS J 2006; 274:551-62. [PMID: 17229156 DOI: 10.1111/j.1742-4658.2006.05609.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hemopexin (HPX), which serves as a scavenger and transporter of toxic plasma heme, has been postulated to play a key role in the homeostasis of NO. In fact, HPX-heme(II) reversibly binds NO and facilitates NO scavenging by O(2). HPX-heme is formed by two four-bladed beta-propeller domains. The heme is bound between the two beta-propeller domains, residues His213 and His266 coordinate the heme iron atom. HPX-heme displays structural features of heme-proteins endowed with (pseudo-)enzymatic activities. In this study, the kinetics of rabbit HPX-heme(III) reductive nitrosylation and peroxynitrite-mediated oxidation of HPX-heme(II)-NO are reported. In the presence of excess NO, HPX-heme(III) is converted to HPX-heme(II)-NO by reductive nitrosylation. The second-order rate constant for HPX-heme(III) reductive nitrosylation is (1.3 +/- 0.1) x 10(1) m(-1).s(-1), at pH 7.0 and 10.0 degrees C. NO binding to HPX-heme(III) is rate limiting. In the absence and presence of CO2 (1.2 x 10(-3) m), excess peroxynitrite reacts with HPX-heme(II)-NO (2.6 x 10(-6) m) leading to HPX-heme(III) and NO, via the transient HPX-heme(III)-NO species. Values of the second-order rate constant for HPX-heme(III)-NO formation are (8.6 +/- 0.8) x 10(4) and (1.2 +/- 0.2) x 10(6) m(-1).s(-1) in the absence and presence of CO2, respectively, at pH 7.0 and 10.0 degrees C. The CO2-independent value of the first-order rate constant for HPX-heme(III)-NO denitrosylation is (4.3 +/- 0.4) x 10(-1) s(-1), at pH 7.0 and 10.0 degrees C. HPX-heme(III)-NO denitrosylation is rate limiting. HPX-heme(II)-NO appears to act as an efficient scavenger of peroxynitrite and of strong oxidants and nitrating species following the reaction of peroxynitrite with CO2 (e.g. ONOOC(O)O-, CO3-, and NO2).
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Affiliation(s)
- Paolo Ascenzi
- Department of Biology and Interdepartmental Laboratory for Electron Microscopy, University Roma Tre, Rome, Italy.
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17
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Fasano M, Antonini G, Ascenzi P. O2-mediated oxidation of hemopexin-heme(II)-NO. Biochem Biophys Res Commun 2006; 345:704-12. [PMID: 16696943 DOI: 10.1016/j.bbrc.2006.04.154] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2006] [Accepted: 04/26/2006] [Indexed: 11/29/2022]
Abstract
Hemopexin (HPX), serving as scavenger and transporter of toxic plasma heme, has been postulated to play a key role in the homeostasis of NO. Here, kinetics of HPX-heme(II) nitrosylation and O2-mediated oxidation of HPX-heme(II)-NO are reported. NO reacts reversibly with HPX-heme(II) yielding HPX-heme(II)-NO, according to the minimum reaction scheme: HPX-heme(II)+NO kon<-->koff HPX-heme(II)-NO values of kon, koff, and K (=kon/koff) are (6.3+/-0.3)x10(3)M-1s-1, (9.1+/-0.4)x10(-4)s-1, and (6.9+/-0.6)x10(6)M-1, respectively, at pH 7.0 and 10.0 degrees C. O2 reacts with HPX-heme(II)-NO yielding HPX-heme(III) and NO3-, by means of the ferric heme-bound peroxynitrite intermediate (HPX-heme(III)-N(O)OO), according to the minimum reaction scheme: HPX-heme(II)-NO+O2 hon<--> HPX-heme(III)-N(O)OO l-->HPX-heme(III)+NO3- the backward reaction rate is negligible. Values of hon and l are (2.4+/-0.3)x10(1)M-1s-1 and (1.4+/-0.2)x10(-3)s-1, respectively, at pH 7.0 and 10.0 degrees C. The decay of HPX-heme(III)-N(O)OO (i.e., l) is rate limiting. The HPX-heme(III)-N(O)OO intermediate has been characterized by optical absorption spectroscopy in the Soret region (lambdamax=409 nm and epsilon409=1.51x10(5)M-1cm-1). These results, representing the first kinetic evidence for HPX-heme(II) nitrosylation and O2-mediated oxidation of HPX-heme(II)-NO, might be predictive of transient (pseudo-enzymatic) function(s) of heme carriers.
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Affiliation(s)
- Mauro Fasano
- Department of Structural and Functional Biology and Center of Neuroscience, University of Insubria, Via Alberto da Giussano 12, I-21052 Busto Arsizio (VA), Italy
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18
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Mauk MR, Rosell FI, Lelj-Garolla B, Moore GR, Mauk AG. Metal ion binding to human hemopexin. Biochemistry 2005; 44:1864-71. [PMID: 15697212 DOI: 10.1021/bi0481747] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Binding of divalent metal ions to human hemopexin (Hx) purified by a new protocol has been characterized by metal ion affinity chromatography and potentiometric titration in the presence and absence of bound protoheme IX. ApoHx was retained by variously charged metal affinity chelate resins in the following order: Ni(2+) > Cu(2+) > Co(2+) > Zn(2+) > Mn(2+). The Hx-heme complex exhibited similar behavior except the order of retention of the complex on Zn(2+)- and Co(2+)-charged columns was reversed. One-dimensional (1)H NMR of apoHx in the presence of Ni(2+) implicates at least two His residues and possibly an Asp, Glu, or Met residue in Ni(2+) binding. Potentiometric titrations establish that apoHx possesses more than two metal ion binding sites and that the capacity and/or affinity for metal ion binding is diminished when heme binds. For most metal ions that have been studied, potentiometric data did not fit to binding isotherms that assume one or two independent binding sites. For Mn(2+), however, these data were consistent with a high-affinity site [K(A) = (15 +/- 3) x 10(6) M(-)(1)] and a low-affinity site (K(A) <or= 2 x10(3) M(-)(1)). Binding of Cu(2+) and Zn(2+) to the Hx-heme complex produced significant changes in the Soret-CD spectrum of the Hx-heme complex that were reversed with addition of EDTA. Possibly, these metal ions bind near the heme binding site and perturb the electronic environment of the heme, or their binding induces exchange of one axial His ligand to the heme iron with another adjacent His residue. A possible role for Hx in the maintenance of metal ion homeostasis is discussed.
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Affiliation(s)
- Marcia R Mauk
- Department of Biochemistry and Molecular Biology and Centre for Blood Research, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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Fasano M, Bocedi A, Mattu M, Coletta M, Ascenzi P. Nitrosylation of rabbit ferrous heme-hemopexin. J Biol Inorg Chem 2004; 9:800-6. [PMID: 15378409 DOI: 10.1007/s00775-004-0598-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2003] [Accepted: 05/13/2004] [Indexed: 10/26/2022]
Abstract
Hemopexin (HPX) serves as a trap for toxic plasma heme, ensuring its complete clearance by transportation to the liver. Moreover, HPX-heme has been postulated to play a key role in the homeostasis of nitric oxide (NO). Here, the thermodynamics for NO binding to rabbit ferrous HPX-heme as well as the EPR and optical absorption spectroscopic properties of rabbit ferrous nitrosylated HPX-heme (HPX-heme-NO) are reported. The value of the dissociation equilibrium constant for NO binding to rabbit ferrous HPX-heme (i.e., H) is (1.4+/-0.2)x10(-7) M, at pH 7.0 and 10.0 degrees C; the value of H is unaffected by sodium chloride. At pH 7.0, rabbit ferrous HPX-heme-NO is a six-coordinate heme-iron species, characterized by an X-band EPR spectrum with an axial geometry and by epsilon=146 mM(-1) cm(-1) at 419 nm. At pH 4.0, rabbit ferrous HPX-heme-NO is a five-coordinate heme-iron species, characterized by an X-band EPR spectrum with three-line splitting centered at 334 mT and by epsilon=74 mM(-1) cm(-1) at 387 nm. The p K(a) value of the reversible pH-induced six- to five-coordinate spectroscopic transition is 4.8+/-0.1 in the absence of sodium chloride and 4.3+/-0.1 in the presence of 1.5x10(-1) M sodium chloride. This result is in agreement with the effect of sodium chloride on rabbit HPX-heme stability. The present data have been analyzed in parallel with those of a related heme model compound and heme-protein systems.
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Affiliation(s)
- Mauro Fasano
- Department of Structural and Functional Biology, University of Insubria, Via Alberto da Giussano 12, 21052 Busto Arsizio (VA), Italy
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21
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Delanghe JR, Langlois MR. Hemopexin: a review of biological aspects and the role in laboratory medicine. Clin Chim Acta 2001; 312:13-23. [PMID: 11580905 DOI: 10.1016/s0009-8981(01)00586-1] [Citation(s) in RCA: 178] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
BACKGROUND Hemopexin is a heme-binding plasma glycoprotein which, after haptoglobin, forms the second line of defense against hemoglobin-mediated oxidative damage during intravascular hemolysis. A decrease in plasma hemopexin concentration reflects a recent release of heme compounds in the extracellular compartment. Heme-hemopexin complexes are delivered to hepatocytes by receptor-mediated endocytosis after which hemopexin is recycled to the circulation. METHODS OF ANALYSIS Immunonephelometric and -turbidimetric hemopexin assays are available as more precise and rapid alternatives to the radial immunodiffusion technique. INTERPRETATIONS Hemopexin determinations are not subject to interference by in vitro hemolysis. Altered serum or plasma concentrations of hemopexin are found not only in hemolytic anemias but also in other conditions such as chronic neuromuscular diseases and acute intermittent porphyria. In laboratory medicine, while hemopexin determination in tandem with haptoglobin has potential applications in the assessment of intravascular hemolysis and allows for the monitoring of the severity of hemolysis after depletion of haptoglobin, its diagnostic utility is less clear in other pathological conditions. Further studies are necessary to fully establish the clinical significance of hemopexin determination.
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Affiliation(s)
- J R Delanghe
- Department of Clinical Chemistry, Ghent University Hospital, De Pintelaan 185, B-9000, Ghent, Belgium.
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Shipulina NV, Smith A, Morgan WT. Effects of reduction and ligation of heme iron on the thermal stability of heme-hemopexin complexes. JOURNAL OF PROTEIN CHEMISTRY 2001; 20:145-54. [PMID: 11563695 DOI: 10.1023/a:1011033625009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Hemopexin has two homologous domains (N- and C-terminal domains), binds 1 mole of heme per mole with high affinity (Kd < 1 pM) in a low-spin bis-histidyl complex, and acts as a transporter for the heme. Transport is accomplished via endocytosis without degradation of the protein. Factors that affect stability of the heme coordination complex and potentially heme release in vivo were examined. The effects of temperature on hemopexin, its N-terminal domain, and their respective ferri-, ferro-, and CO-ferro-heme complexes were studied using absorbance and circular dichroism (CD) spectroscopy. As monitored with second-derivative absorbance spectra, the higher order structure of apo-hemopexin unfolds with a Tm of 52 degrees C in 50 mM sodium phosphate buffer and is stabilized by 150 mM NaCl (Tm 63 degrees C). Bis-histidyl heme coordination by hemopexin, observed by Soret absorbance, is substantially weakened by reduction of ferri-heme-hemopexin (Tm 55.5 degrees C) to the ferro-heme form (Tm 48 degrees C), and NaCl stabilizes both complexes by 10-15 degrees C. CO binding to ferroheme-hemopexin restores complex stability (Tm 67 degrees C). Upon cooling, unfolded apo- and ferriheme-hemopexin extensively refold and recover substantial heme-binding activity, but the characteristic ellipticity of the native protein (UV region) and heme complex (Soret region) are not regained, indicating that altered refolded forms are produced. Lowering the pH from 7.4 to 6.5 has little effect on the stability of the apo-protein but increases the Tm of heme complexes by 5-12 degrees C. The stability of the apo-N-terminal domain (Tm 53 degrees C) is similar to that of intact hemopexin, and the ferri-, ferro-, and CO-ferro-heme complexes of the N-terminal domain have Tm values of 53 degrees C, 33 degrees C, and 75 degrees C, respectively.
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Affiliation(s)
- N V Shipulina
- Division of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City, 64110, USA
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