1
|
Özdemir M, Köksoy B, Ceyhan D, Sayın K, Erçağ E, Bulut M, Yalçın B. Design and in silico study of the novel coumarin derivatives against SARS-CoV-2 main enzymes. J Biomol Struct Dyn 2022; 40:4905-4920. [PMID: 33357038 PMCID: PMC7784838 DOI: 10.1080/07391102.2020.1863263] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 12/08/2020] [Indexed: 01/18/2023]
Abstract
The novel coronavirus (SARS-CoV-2) causes severe acute respiratory syndrome and can be fatal. In particular, antiviral drugs that are currently available to treat infection in the respiratory tract have been experienced, but there is a need for new antiviral drugs that are targeted and inhibit coronavirus. The antiviral properties of organic compounds found in nature, especially coumarins, are known and widely studied. Coumarins, which are also metabolites in many medicinal drugs, should be investigated as inhibitors against coronavirus due to their pharmacophore properties (low toxicity and high pharmacokinetic properties). The easy addition of substituents to the chemical structures of coumarins makes these structures unique for the drug design. This study focuses on factors that increase the molecular binding and antiviral properties of coumarins. Molecular docking studies have been carried out to five different proteins (Spike S1-subunit, NSP5, NSP12, NSP15, and NSP16) of the SARS-CoV-2 and two proteins (ACE2 and VKORC1) of human. The best binding scores for 17 coumarins were determined for NSP12 (NonStructural Protein-12). The highest score (-10.01 kcal/mol) in the coumarin group is 2-morpholinoethan-1-amine substituted coumarin. Molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) analyses of selected ligand-protein complexes were performed. The binding energies in each 5 ns were calculated and it was found that the interaction between ligand and target protein were stable.Communicated by Ramaswamy H. Sarma.
Collapse
Affiliation(s)
- Mücahit Özdemir
- Department of Chemistry, Marmara University, Istanbul, Turkey
| | - Baybars Köksoy
- Department of Chemistry, Bursa Technical University, Bursa, Turkey
| | - Deniz Ceyhan
- Department of Chemistry, Tekirdağ Namık Kemal University, Tekirdağ, Turkey
| | - Koray Sayın
- Department of Chemistry, Sivas Cumhuriyet University, Sivas, Turkey
- Advanced Technology Research and Application Center, Sivas Cumhuriyet University, Sivas, Turkey
| | - Erol Erçağ
- Department of Chemistry, Tekirdağ Namık Kemal University, Tekirdağ, Turkey
| | - Mustafa Bulut
- Department of Chemistry, Marmara University, Istanbul, Turkey
| | - Bahattin Yalçın
- Department of Chemistry, Marmara University, Istanbul, Turkey
| |
Collapse
|
2
|
Holcomb D, Alexaki A, Hernandez N, Hunt R, Laurie K, Kames J, Hamasaki-Katagiri N, Komar AA, DiCuccio M, Kimchi-Sarfaty C. Gene variants of coagulation related proteins that interact with SARS-CoV-2. PLoS Comput Biol 2021; 17:e1008805. [PMID: 33730015 PMCID: PMC8007013 DOI: 10.1371/journal.pcbi.1008805] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 03/29/2021] [Accepted: 02/15/2021] [Indexed: 12/30/2022] Open
Abstract
Thrombosis is a recognized complication of Coronavirus disease of 2019 (COVID-19) and is often associated with poor prognosis. There is a well-recognized link between coagulation and inflammation, however, the extent of thrombotic events associated with COVID-19 warrants further investigation. Poly(A) Binding Protein Cytoplasmic 4 (PABPC4), Serine/Cysteine Proteinase Inhibitor Clade G Member 1 (SERPING1) and Vitamin K epOxide Reductase Complex subunit 1 (VKORC1), which are all proteins linked to coagulation, have been shown to interact with SARS proteins. We computationally examined the interaction of these with SARS-CoV-2 proteins and, in the case of VKORC1, we describe its binding to ORF7a in detail. We examined the occurrence of variants of each of these proteins across populations and interrogated their potential contribution to COVID-19 severity. Potential mechanisms, by which some of these variants may contribute to disease, are proposed. Some of these variants are prevalent in minority groups that are disproportionally affected by severe COVID-19. Therefore, we are proposing that further investigation around these variants may lead to better understanding of disease pathogenesis in minority groups and more informed therapeutic approaches.
Collapse
Affiliation(s)
- David Holcomb
- Center for Biologics Evaluation and Research, Office of Tissues and Advanced Therapies, Division of Plasma Protein Therapeutics, Food and Drug Administration, Silver Spring, Maryland, United States of America
| | - Aikaterini Alexaki
- Center for Biologics Evaluation and Research, Office of Tissues and Advanced Therapies, Division of Plasma Protein Therapeutics, Food and Drug Administration, Silver Spring, Maryland, United States of America
| | - Nancy Hernandez
- Center for Biologics Evaluation and Research, Office of Tissues and Advanced Therapies, Division of Plasma Protein Therapeutics, Food and Drug Administration, Silver Spring, Maryland, United States of America
| | - Ryan Hunt
- Center for Biologics Evaluation and Research, Office of Tissues and Advanced Therapies, Division of Plasma Protein Therapeutics, Food and Drug Administration, Silver Spring, Maryland, United States of America
| | - Kyle Laurie
- Center for Biologics Evaluation and Research, Office of Tissues and Advanced Therapies, Division of Plasma Protein Therapeutics, Food and Drug Administration, Silver Spring, Maryland, United States of America
| | - Jacob Kames
- Center for Biologics Evaluation and Research, Office of Tissues and Advanced Therapies, Division of Plasma Protein Therapeutics, Food and Drug Administration, Silver Spring, Maryland, United States of America
| | - Nobuko Hamasaki-Katagiri
- Center for Biologics Evaluation and Research, Office of Tissues and Advanced Therapies, Division of Plasma Protein Therapeutics, Food and Drug Administration, Silver Spring, Maryland, United States of America
| | - Anton A. Komar
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological and Environmental Sciences, Cleveland State University, Cleveland, Ohio, United States of America
| | - Michael DiCuccio
- National Center of Biotechnology Information, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (MD); (CKS)
| | - Chava Kimchi-Sarfaty
- Center for Biologics Evaluation and Research, Office of Tissues and Advanced Therapies, Division of Plasma Protein Therapeutics, Food and Drug Administration, Silver Spring, Maryland, United States of America
- * E-mail: (MD); (CKS)
| |
Collapse
|
3
|
Holcomb D, Alexaki A, Hernandez N, Laurie K, Kames J, Hamasaki-Katagiri N, Komar AA, DiCuccio M, Kimchi-Sarfaty C. Potential impact on coagulopathy of gene variants of coagulation related proteins that interact with SARS-CoV-2. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2020. [PMID: 32935103 DOI: 10.1101/2020.09.08.272328] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Thrombosis has been one of the complications of the Coronavirus disease of 2019 (COVID-19), often associated with poor prognosis. There is a well-recognized link between coagulation and inflammation, however, the extent of thrombotic events associated with COVID-19 warrants further investigation. Poly(A) Binding Protein Cytoplasmic 4 (PABPC4), Serine/Cysteine Proteinase Inhibitor Clade G Member 1 (SERPING1) and Vitamin K epOxide Reductase Complex subunit 1 (VKORC1), which are all proteins linked to coagulation, have been shown to interact with SARS proteins. We computationally examined the interaction of these with SARS-CoV-2 proteins and, in the case of VKORC1, we describe its binding to ORF7a in detail. We examined the occurrence of variants of each of these proteins across populations and interrogated their potential contribution to COVID-19 severity. Potential mechanisms by which some of these variants may contribute to disease are proposed. Some of these variants are prevalent in minority groups that are disproportionally affected by severe COVID-19. Therefore, we are proposing that further investigation around these variants may lead to better understanding of disease pathogenesis in minority groups and more informed therapeutic approaches. Author summary Increased blood clotting, especially in the lungs, is a common complication of COVID-19. Infectious diseases cause inflammation which in turn can contribute to increased blood clotting. However, the extent of clot formation that is seen in the lungs of COVID-19 patients suggests that there may be a more direct link. We identified three human proteins that are involved indirectly in the blood clotting cascade and have been shown to interact with proteins of SARS virus, which is closely related to the novel coronavirus. We examined computationally the interaction of these human proteins with the viral proteins. We looked for genetic variants of these proteins and examined how these variants are distributed across populations. We investigated whether variants of these genes could impact severity of COVID-19. Further investigation around these variants may provide clues for the pathogenesis of COVID-19 particularly in minority groups.
Collapse
|
4
|
Beato S, Marques C, Laizé V, Gavaia PJ, Fernández I. New Insights on Vitamin K Metabolism in Senegalese sole ( Solea senegalensis) Based on Ontogenetic and Tissue-Specific Vitamin K Epoxide Reductase Molecular Data. Int J Mol Sci 2020; 21:E3489. [PMID: 32429051 PMCID: PMC7278968 DOI: 10.3390/ijms21103489] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 05/07/2020] [Accepted: 05/13/2020] [Indexed: 12/17/2022] Open
Abstract
Vitamin K (VK) is a key nutrient for several biological processes (e.g., blood clotting and bone metabolism). To fulfill VK nutritional requirements, VK action as an activator of pregnane X receptor (Pxr) signaling pathway, and as a co-factor of γ-glutamyl carboxylase enzyme, should be considered. In this regard, VK recycling through vitamin K epoxide reductases (Vkors) is essential and should be better understood. Here, the expression patterns of vitamin K epoxide reductase complex subunit 1 (vkorc1) and vkorc1 like 1 (vkorc1l1) were determined during the larval ontogeny of Senegalese sole (Solea senegalensis), and in early juveniles cultured under different physiological conditions. Full-length transcripts for ssvkorc1 and ssvkorc1l1 were determined and peptide sequences were found to be evolutionarily conserved. During larval development, expression of ssvkorc1 showed a slight increase during absence or low feed intake. Expression of ssvkorc1l1 continuously decreased until 24 h post-fertilization, and remained constant afterwards. Both ssvkors were ubiquitously expressed in adult tissues, and highest expression was found in liver for ssvkorc1, and ovary and brain for ssvkorc1l1. Expression of ssvkorc1 and ssvkorc1l1 was differentially regulated under physiological conditions related to fasting and re-feeding, but also under VK dietary supplementation and induced deficiency. The present work provides new and basic molecular clues evidencing how VK metabolism in marine fish is sensitive to nutritional and environmental conditions.
Collapse
Affiliation(s)
- Silvia Beato
- Campus de Vegazana, Universidad de León (ULE), s/n, 24071 León, Spain;
| | - Carlos Marques
- Centro de Ciências do Mar (CCMAR), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal; (C.M.); (V.L.); (P.J.G.)
| | - Vincent Laizé
- Centro de Ciências do Mar (CCMAR), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal; (C.M.); (V.L.); (P.J.G.)
| | - Paulo J. Gavaia
- Centro de Ciências do Mar (CCMAR), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal; (C.M.); (V.L.); (P.J.G.)
- Departamento de Ciências Biomédicas e Medicina (DCBM), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
| | - Ignacio Fernández
- Center for Aquaculture Research, Agrarian Technological Institute of Castile and Leon, Ctra. Arévalo, S/n. Zamarramala, 40196 Segovia, Spain
| |
Collapse
|
5
|
Abstract
Ca2+ binding proteins (CBP) are of key importance for calcium to play its role as a pivotal second messenger. CBP bind Ca2+ in specific domains, contributing to the regulation of its concentration at the cytosol and intracellular stores. They also participate in numerous cellular functions by acting as Ca2+ transporters across cell membranes or as Ca2+-modulated sensors, i.e. decoding Ca2+ signals. Since CBP are integral to normal physiological processes, possible roles for them in a variety of diseases has attracted growing interest in recent years. In addition, research on CBP has been reinforced with advances in the structural characterization of new CBP family members. In this chapter we have updated a previous review on CBP, covering in more depth potential participation in physiopathological processes and candidacy for pharmacological targets in many diseases. We review intracellular CBP that contain the structural EF-hand domain: parvalbumin, calmodulin, S100 proteins, calcineurin and neuronal Ca2+ sensor proteins (NCS). We also address intracellular CBP lacking the EF-hand domain: annexins, CBP within intracellular Ca2+ stores (paying special attention to calreticulin and calsequestrin), proteins that contain a C2 domain (such as protein kinase C (PKC) or synaptotagmin) and other proteins of interest, such as regucalcin or proprotein convertase subtisilin kexins (PCSK). Finally, we summarise the latest findings on extracellular CBP, classified according to their Ca2+ binding structures: (i) EF-hand domains; (ii) EGF-like domains; (iii) ɣ-carboxyl glutamic acid (GLA)-rich domains; (iv) cadherin domains; (v) Ca2+-dependent (C)-type lectin-like domains; (vi) Ca2+-binding pockets of family C G-protein-coupled receptors.
Collapse
|
6
|
VKORC1 and VKORC1L1 have distinctly different oral anticoagulant dose-response characteristics and binding sites. Blood Adv 2019; 2:691-702. [PMID: 29581108 DOI: 10.1182/bloodadvances.2017006775] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 01/22/2018] [Indexed: 01/11/2023] Open
Abstract
Vitamin K reduction is catalyzed by 2 enzymes in vitro: the vitamin K 2,3-epoxide reductase complex subunit 1 (VKORC1) and its isozyme VKORC1-like1 (VKORC1L1). In vivo, VKORC1 reduces vitamin K to sustain γ-carboxylation of vitamin K-dependent proteins, including coagulation factors. Inhibition of VKORC1 by oral anticoagulants (OACs) is clinically used in therapy and in prevention of thrombosis. However, OACs also inhibit VKORC1L1, which was previously shown to play a role in intracellular redox homeostasis in vitro. Here, we report data for the first time on specific inhibition of both VKOR enzymes for various OACs and rodenticides examined in a cell-based assay. Effects on endogenous VKORC1 and VKORC1L1 were independently investigated in genetically engineered HEK 293T cells that were knocked out for the respective genes by CRISPR/Cas9 technology. In general, dose-responses for 4-hydroxycoumarins and 1,3-indandiones were enzyme-dependent, with lower susceptibility for VKORC1L1 compared with VKORC1. In contrast, rodenticides exhibited nearly identical dose-responses for both enzymes. To explain the distinct inhibition pattern, we performed in silico modeling suggesting different warfarin binding sites for VKORC1 and VKORC1L1. We identified arginine residues at positions 38, 42, and 68 in the endoplasmatic reticulum luminal loop of VKORC1L1 responsible for charge-stabilized warfarin binding, resulting in a binding pocket that is diametrically opposite to that of VKORC1. In conclusion, our findings provide insight into structural and molecular drug binding on VKORC1, and especially on VKORC1L1.
Collapse
|
7
|
Abstract
Vitamin K (VK) is an essential cofactor for the post-translational conversion of peptide-bound glutamate to γ-carboxyglutamate. The resultant vitamin K-dependent proteins are known or postulated to possess a variety of biological functions, chiefly in the maintenance of hemostasis. The vitamin K cycle is a cellular pathway that drives γ-carboxylation and recycling of VK via γ-carboxyglutamyl carboxylase (GGCX) and vitamin K epoxide reductase (VKOR), respectively. In this review, we show how novel molecular biological approaches are providing new insights into the pathophysiological mechanisms caused by rare mutations of both GGCX and VKOR. We also discuss how other protein regulators influence the intermediary metabolism of VK, first through intestinal absorption and second through a pathway that converts some dietary phylloquinone to menadione, which is prenylated to menaquinone-4 (MK-4) in target tissues by UBIAD1. The contribution of MK-4 synthesis to VK functions is yet to be revealed.
Collapse
Affiliation(s)
- Martin J Shearer
- Centre for Haemostasis and Thrombosis, Guy's and St Thomas' NHS Foundation Trust, London SE1 7EH, United Kingdom;
| | - Toshio Okano
- Department of Hygienic Sciences, Kobe Pharmaceutical University, Kobe 658-8558 Japan;
| |
Collapse
|
8
|
Chatron N, Chalmond B, Trouvé A, Benoît E, Caruel H, Lattard V, Tchertanov L. Identification of the functional states of human vitamin K epoxide reductase from molecular dynamics simulations. RSC Adv 2017. [DOI: 10.1039/c7ra07463h] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The functionally-related states of hVKORC1 predicted from MD conformations were assigned by probing their affinity to vitamin K and validated through analysis of its binding energy with VKAs.
Collapse
Affiliation(s)
- N. Chatron
- Centre de Mathématiques et de Leurs Applications (CMLA)
- ENS Cachan
- CNRS
- Université Paris-Saclay
- Cachan
| | - B. Chalmond
- Centre de Mathématiques et de Leurs Applications (CMLA)
- ENS Cachan
- CNRS
- Université Paris-Saclay
- Cachan
| | - A. Trouvé
- Centre de Mathématiques et de Leurs Applications (CMLA)
- ENS Cachan
- CNRS
- Université Paris-Saclay
- Cachan
| | - E. Benoît
- USC 1233 INRA-Vetagro Sup
- Veterinary School of Lyon
- Marcy l'Etoile
- France
| | | | - V. Lattard
- USC 1233 INRA-Vetagro Sup
- Veterinary School of Lyon
- Marcy l'Etoile
- France
| | - L. Tchertanov
- Centre de Mathématiques et de Leurs Applications (CMLA)
- ENS Cachan
- CNRS
- Université Paris-Saclay
- Cachan
| |
Collapse
|
9
|
Czogalla KJ, Biswas A, Höning K, Hornung V, Liphardt K, Watzka M, Oldenburg J. Warfarin and vitamin K compete for binding to Phe55 in human VKOR. Nat Struct Mol Biol 2016; 24:77-85. [PMID: 27941861 DOI: 10.1038/nsmb.3338] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 11/08/2016] [Indexed: 11/09/2022]
Abstract
Vitamin K epoxide reductase (VKOR) catalyzes the reduction of vitamin K quinone and vitamin K 2,3-epoxide, a process essential to sustain γ-carboxylation of vitamin K-dependent proteins. VKOR is also a therapeutic target of warfarin, a treatment for thrombotic disorders. However, the structural and functional basis of vitamin K reduction and the antagonism of warfarin inhibition remain elusive. Here, we identified putative binding sites of both K vitamers and warfarin on human VKOR. The predicted warfarin-binding site was verified by shifted dose-response curves of specified mutated residues. We used CRISPR-Cas9-engineered HEK 293T cells to assess the vitamin K quinone and vitamin K 2,3-epoxide reductase activities of VKOR variants to characterize the vitamin K naphthoquinone head- and isoprenoid side chain-binding regions. Our results challenge the prevailing concept of noncompetitive warfarin inhibition because K vitamers and warfarin share binding sites on VKOR that include Phe55, a key residue binding either the substrate or inhibitor.
Collapse
Affiliation(s)
- Katrin J Czogalla
- Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany
| | - Arijit Biswas
- Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany
| | - Klara Höning
- Institute of Molecular Medicine, University Hospital Bonn, Bonn, Germany
| | - Veit Hornung
- Institute of Molecular Medicine, University Hospital Bonn, Bonn, Germany.,Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Kerstin Liphardt
- Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany
| | - Matthias Watzka
- Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany.,Center for Rare Diseases Bonn (ZSEB), University Clinic Bonn, Bonn, Germany
| | - Johannes Oldenburg
- Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany.,Center for Rare Diseases Bonn (ZSEB), University Clinic Bonn, Bonn, Germany
| |
Collapse
|
10
|
Dufrisne MB, Petrou VI, Clarke OB, Mancia F. Structural basis for catalysis at the membrane-water interface. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1862:1368-1385. [PMID: 27913292 DOI: 10.1016/j.bbalip.2016.11.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 11/22/2016] [Accepted: 11/23/2016] [Indexed: 11/27/2022]
Abstract
The membrane-water interface forms a uniquely heterogeneous and geometrically constrained environment for enzymatic catalysis. Integral membrane enzymes sample three environments - the uniformly hydrophobic interior of the membrane, the aqueous extramembrane region, and the fuzzy, amphipathic interfacial region formed by the tightly packed headgroups of the components of the lipid bilayer. Depending on the nature of the substrates and the location of the site of chemical modification, catalysis may occur in each of these environments. The availability of structural information for alpha-helical enzyme families from each of these classes, as well as several beta-barrel enzymes from the bacterial outer membrane, has allowed us to review here the different ways in which each enzyme fold has adapted to the nature of the substrates, products, and the unique environment of the membrane. Our focus here is on enzymes that process lipidic substrates. This article is part of a Special Issue entitled: Bacterial Lipids edited by Russell E. Bishop.
Collapse
Affiliation(s)
- Meagan Belcher Dufrisne
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
| | - Vasileios I Petrou
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
| | - Oliver B Clarke
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Filippo Mancia
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA.
| |
Collapse
|
11
|
The membrane topology of vitamin K epoxide reductase is conserved between human isoforms and the bacterial enzyme. Biochem J 2016; 473:851-8. [PMID: 26772871 DOI: 10.1042/bj20151223] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 01/15/2016] [Indexed: 11/17/2022]
Abstract
The membrane topology of vitamin K epoxide reductase (VKOR) is controversial with data supporting both a three transmembrane and a four transmembrane model. The positioning of the transmembrane domains and the loops between these domains is critical if we are to understand the mechanism of vitamin K oxidation and its recycling by members of the thioredoxin family of proteins and the mechanism of action of warfarin, an inhibitor of VKOR. Here we show that both mammalian VKOR isoforms adopt the same topology, with the large loop between transmembrane one and two facing the lumen of the endoplasmic reticulum (ER). We used a redox sensitive green fluorescent protein (GFP) fused to the N- or C-terminus to show that these regions face the cytosol, and introduction of glycosylation sites along with mixed disulfide formation with thioredoxin-like transmembrane protein (TMX) to demonstrate ER localization of the major loop. The topology is identical with the bacterial homologue from Synechococcussp., for which the structure and mechanism of recycling has been characterized. Our results provide a resolution to the membrane topology controversy and support previous results suggesting a role for members of the ER protein disulfide isomerase (PDI) family in recycling VKOR.
Collapse
|