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Ershov PV, Yablokov E, Zgoda V, Mezentsev Y, Gnedenko O, Kaluzhskiy L, Svirid A, Gilep A, Usanov SA, Ivanov A. A new insight into subinteractomes of functional antagonists: Thromboxane (CYP5A1) and prostacyclin (CYP8A1) synthases. Cell Biol Int 2021; 45:1175-1182. [PMID: 33527589 DOI: 10.1002/cbin.11564] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 11/10/2020] [Accepted: 01/31/2021] [Indexed: 12/14/2022]
Abstract
The current article aims to summarize all possible spectrum of protein-protein interactions for thromboxane A synthase (CYP5A1) and prostacyclin synthase (CYP8A1). These enzymes metabolize the same substrate (prostaglandin H2 ) and can participate in cardiovascular, inflammatory, immune processes, and apoptosis modulation, as well as significantly influence the risk of cancers. Binary protein-protein and multiprotein complexes are of great importance in enzyme-regulating and signal-transduction pathways. However, protein partners of CYP5A1 and CYP8A1 are not yet fully identified, although both synthases are considered as prospective drug targets. At least 36 novel protein partners of CYP5A1 and CYP8A1 were revealed from different tissue types using an approach based on affinity isolation and mass spectrometry. Enrichment analysis showed that these proteins have different molecular functions: folding (refolding), unfolded protein and chaperon binding, protein transport (export/import), posttranslational modification, protein domain-specific binding, antioxidant activity, and glutathione homeostasis. A significant part of them, belonging to molecular chaperones, were common partners for CYP5A1 and CYP8A1, while other proteins were unique with the tissue-dependent distribution. New aspects of CYP5A1 and CYP8A1 interactomics and hetero-complex formation with different protein partners, including cytochrome P450s are discussed.
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Affiliation(s)
- Pavel V Ershov
- Federal State Budgetary Institution "V.N. Orekhovich Research Institute of Biomedical Chemistry", Moscow, Russia.,Federal State Budgetary Institution, Centre for Strategic Planning and Management of Biomedical Health Risks, The Federal Medical Biological Agency, Moscow, Russia
| | - Evgeniy Yablokov
- Federal State Budgetary Institution "V.N. Orekhovich Research Institute of Biomedical Chemistry", Moscow, Russia
| | - Victor Zgoda
- Federal State Budgetary Institution "V.N. Orekhovich Research Institute of Biomedical Chemistry", Moscow, Russia
| | - Yuri Mezentsev
- Federal State Budgetary Institution "V.N. Orekhovich Research Institute of Biomedical Chemistry", Moscow, Russia
| | - Oksana Gnedenko
- Federal State Budgetary Institution "V.N. Orekhovich Research Institute of Biomedical Chemistry", Moscow, Russia
| | - Leonid Kaluzhskiy
- Federal State Budgetary Institution "V.N. Orekhovich Research Institute of Biomedical Chemistry", Moscow, Russia
| | - Andrey Svirid
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, Minsk, Republic of Belarus
| | - Andrei Gilep
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, Minsk, Republic of Belarus
| | - Sergey A Usanov
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, Minsk, Republic of Belarus
| | - Alexis Ivanov
- Federal State Budgetary Institution "V.N. Orekhovich Research Institute of Biomedical Chemistry", Moscow, Russia
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Smith KJ, Skelton H. Arachidonic Acid-Derived Bioactive Lipids: Their Role and the Role for Their Inhibitors in Dermatology. J Cutan Med Surg 2016. [DOI: 10.1177/120347540200600309] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Background: In addition to corticosteroids, there are increasing numbers of anti-inflammatory agents that specifically target bioactive lipids generated from arachidonic acid. Knowledge of the diverse mechanisms of action of these different bioactive lipids holds promise in the therapy of a wide spectrum of cutaneous and systemic disorders. Objective: Therapeutic manipulations of these lipid molecules through inhibition, stimulation, or direct replacement have broad physiologic effects. These therapeutic strategies not only modulate inflammation, pain, and hemostatic parameters, they also play a role in cardiac, respiratory, renal, and gastrointestinal function and disease, as well as in angiogenesis and in factors that control cell growth and apoptosis important in carcinogenesis. Conclusion: Newer drug discovery methods, including combinatorial chemistry with molecular modeling, have made it possible to develop inhibitors and analogs with increasing specificity and bioactivity and decreasing toxicity. Although the application of these analogs and inhibitors for cutaneous disease is limited today, either as primary agents or adjuvant therapy, these drugs will have a place in our therapeutic regimes of the future. We present a review of the therapeutic agents now available from manipulation of these bioactive lipids, and their role and future in dermatology.
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Affiliation(s)
- Kathleen J. Smith
- The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army, the Department of the Navy, or the Department of Defense
| | - Henry Skelton
- The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army, the Department of the Navy, or the Department of Defense
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Audran G, Brémond P, Marque SR, Siri D, Santelli M. Energetics of the biosynthesis of prostanes from arachidonate. Tetrahedron 2015. [DOI: 10.1016/j.tet.2015.07.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Yanai TK, Mori S. Density functional studies on thromboxane biosynthesis: mechanism and role of the heme-thiolate system. Chem Asian J 2009; 3:1900-11. [PMID: 18844316 DOI: 10.1002/asia.200800253] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Reaction mechanisms for the isomerization of prostaglandin H(2) to thromboxane A(2), and degradation to 12-L-hydroxy-5,8,10-heptadecatrienoic acid (HHT) and malondialdehyde (MDA), catalyzed by thromboxane synthase, were investigated using the unrestricted Becke-three-parameter plus Lee-Yang-Parr (UB3LYP) density functional level theory. In addition to the reaction pathway through Fe(IV)-porphyrin intermediates, a new reaction pathway through Fe(III)-porphyrin pi-cation radical intermediates was found. Both reactions proceed with the homolytic cleavage of endoperoxide O-O to give an alkoxy radical. This intermediate converts into an allyl radical intermediate by a C-C homolytic cleavage, followed by the formation of thromboxane A(2) having a 6-membered ring through a one electron transfer, or the degradation into HHT and MDA. The proposed mechanism shows that an iron(III)-containing system having electron acceptor ability is essential for the 6-membered ring formation leading to thromboxane A(2). Our results suggest that the step of the endoperoxide O-O homolytic bond cleavage has the highest activation energy following the binding of prostaglandin H(2) to thromboxane synthase.
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Affiliation(s)
- Tetsuya K Yanai
- Faculty of Science, Ibaraki University, Bunkyo, Mito 310-8512, Japan
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Marchand A, Barouki R, Garlatti M. Regulation of NAD(P)H:Quinone Oxidoreductase 1 Gene Expression by CYP1A1 Activity. Mol Pharmacol 2004; 65:1029-37. [PMID: 15044633 DOI: 10.1124/mol.65.4.1029] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The dioxin 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD) induces phase I and II xenobiotic metabolizing enzymes (XME) which act sequentially to eliminate different classes of xenobiotics. The transcriptional effects of TCDD are generally mediated by the arylhydrocarbon receptor (AhR). We hypothesized that TCDD could also act indirectly, by increasing the activity of cytochrome P450 1A1 (CYP1A1), a phase I gene, which could then mediate the induction of other XME genes, such as the NAD(P)H:quinone oxidoreductase 1 (NQO1). To test this hypothesis, NQO1 gene expression was monitored after either overexpression of CYP1A1 or siRNA-mediated knock-down of CYP1A1 activity in the hepatoma cell line HepG2. Overexpression of CYP1A1 in the absence of TCDD was carried out using either adenoviral infection or the "Tet-off" system. Recombinant adenoviruses were produced encoding no protein, CYP1A1 (Ad1A1), or a mutated inactive CYP1A1 (Ad1A1mut). In the HepG2 Tet-off cell line, CYP1A1 expression was induced by the removal of doxycycline (dox) from the cell medium. Ad1A1 infection or dox removal induced CYP1A1 activity and H(2)O(2) production similarly to TCDD treatment. Moreover, in both systems, the amount of NQO1 mRNA increased to the same level as after TCDD treatment (approximately 2-fold). The UDP-glucuronosyl transferase 1A6 (UGT1A6) gene is also similarly regulated. NQO1 gene expression was not induced when mutant, inactive CYP1A1 was overexpressed or when the antioxidant N-acetyl cysteine (NAC) was added to Ad1A1. Finally, either NAC or siRNA directed against CYP1A1 mRNA decreased the induction of NQO1 gene expression by TCDD. We conclude that, after exposure to TCDD, the NQO1 gene expression can be controlled by CYP1A1 activity through an oxidative stress mediated pathway.
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Affiliation(s)
- A Marchand
- Institut National de la Santé et de la Recherche Médicale, Unité-490, 45 rue des Saints-Pères, 75006 Paris, France.
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Hsu PY, Wang LH. Protein engineering of thromboxane synthase: conversion of membrane-bound to soluble form. Arch Biochem Biophys 2003; 416:38-46. [PMID: 12859980 DOI: 10.1016/s0003-9861(03)00287-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Thromboxane A2 synthase (TXAS) binds to the endoplasmic reticulum membrane and catalyzes both an isomerization of prostaglandin H2 (PGH2) to form thromboxane A2 (TXA2) and a fragmentation of PGH2 to form 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT) and malondialdehyde (MDA). TXAS is a non-classic cytochrome P450 in that it does not require molecular oxygen or an external electron donor for catalysis. Difficulty in obtaining crystals from the membrane-bound TXAS prompted us to modify the protein to a soluble form. Results from site-directed mutagenesis, hydropathy analysis, and homology modeling led us to identify a putative membrane association segment near the end of helix F in TXAS. We report here the generation of a soluble form of TXAS by deletion of the amino-terminal membrane-anchoring domain and replacement of the helix F and F-G loop region with the corresponding region of the structurally characterized microsomal P450 2C5. The resultant TXAS/2C5 chimera is expressed in bacteria as a cytosolic and monomeric protein. Addition of an amino-terminal leader sequence to enhance expression and a tetra-histidine segment at the carboxyl-terminus to facilitate purification yielded approximately 4 mg of nearly homogeneous TXAS/2C5 per liter of bacterial culture. The TXAS/2C5 chimera contains heme at nearly a 1:1 molar ratio and catalyzes the formation of TXA2, MDA, and HHT at a 1:1:1 ratio, although with a reduced catalytic activity compared to wild type TXAS. TXAS/2C5 exhibits electronic absorption spectra similar to wild type TXAS and has similar affinities toward distal heme ligands such as imidazole and U44069. The chimera was mono-dispersive and thus is promising for crystallization trials.
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Affiliation(s)
- Pei-Yung Hsu
- Division of Hematology, Department of Internal Medicine, University of Texas-Houston, 6431 Fannin, Houston, TX 77030, USA
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Nakayama T, Soma M, Watanabe Y, Hasimu B, Sato M, Aoi N, Kosuge K, Kanmatsuse K, Kokubun S, Marrow JD, Oates JA. Splicing mutation of the prostacyclin synthase gene in a family associated with hypertension. Biochem Biophys Res Commun 2002; 297:1135-9. [PMID: 12372404 DOI: 10.1016/s0006-291x(02)02341-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Prostacyclin inhibits platelet aggregation, smooth muscle cell proliferation, and vasoconstriction. The prostacyclin synthase (PGIS) gene is a candidate gene for cardiovascular disease. The purpose of this study was to locate possible mutations in the PGIS gene related to hypertension and cerebral infarction. Using the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) method, we discovered a T to C transition at the +2 position of the splicing donor site of intron 9 in patients with essential hypertension (EH). In vitro expression analysis of an allelic minigene consisting of exons 8-10 revealed that the nucleotide transition causes skipping of exon 9. This in turn alters the translational reading frame of exon 10 and introduces a premature stop codon (TGA). A three-dimensional model shows that the splice site mutation produces a truncated protein with a deletion in the heme-binding region. This splice site mutation was found in only one subject in 200 EH patients and 200 healthy controls. Analysis of the patient's family members revealed the mutation in two of the three siblings. The urinary excretion of prostacyclin metabolites in subjects with the mutation was significantly decreased. All subjects displaying the splice site mutation in the PGIS gene were hypertensive. In this study, we report a novel splicing mutation in the PGIS gene, which is associated with hypertension in a family. It is thought that this mechanism may involve in the pathophysiology of their hypertension.
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Affiliation(s)
- Tomohiro Nakayama
- Division of Receptor Biology, Advanced Medical Research Center, Nihon University School of Medicine, Ooyaguchi-kamimachi 30-1, Itabashi-ku, 173-8610, Tokyo, Japan.
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9
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Wang LH, Kulmacz RJ. Thromboxane synthase: structure and function of protein and gene. Prostaglandins Other Lipid Mediat 2002; 68-69:409-22. [PMID: 12432933 DOI: 10.1016/s0090-6980(02)00045-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Lee-Ho Wang
- Department of Internal Medicine, University of Texas Health Science Center at Houston, 77030, USA.
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Chevalier D, Lo-Guidice JM, Sergent E, Allorge D, Debuysère H, Ferrari N, Libersa C, Lhermitte M, Broly F. Identification of genetic variants in the human thromboxane synthase gene (CYP5A1). Mutat Res 2001; 432:61-7. [PMID: 11465543 DOI: 10.1016/s1383-5726(00)00004-2] [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: 11/20/2022]
Abstract
Thromboxane synthase (CYP5A1) catalyzes the conversion of prostaglandin H2 to thromboxane A2, a potent mediator of platelet aggregation, vasoconstriction and bronchoconstriction. It has been implicated in the patho-physiological process of a variety of diseases, such as atherosclerosis, myocardial infarction, stroke and asthma. On the basis of the hypothesis that variations of the CYP5A1 gene may play an important role in human diseases, we performed a screening for variations in the human CYP5A1 gene sequence. We examined genomic DNA from 200 individuals, for mutations in the promoter region, the protein encoding sequences and the 3'-untranslated region of the CYP5A1. Eleven polymorphisms have been identified in the CYP5A1 gene including eight missense mutations R61H, D161E, N246S, L357V, Q417E, E450K, T451N and R466Q. This is the first report of genetic variants in the human CYP5A1 altering the protein sequence. The effect of these variants on the metabolic activity of CYP5A1 remains to be further evaluated.
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Affiliation(s)
- D Chevalier
- Laboratoire de Biochimie et Biologie Moléculaire, Hĵpital Calmette et, Faculté de Médecine, Lille, France.
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11
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Abstract
Thromboxane A2 is a biologically potent arachidonate metabolite through the cyclooxygenase pathway. It induces platelet aggregation and smooth muscle contraction and may promote mitogenesis and apoptosis of other cells. Its roles in physiological and pathological conditions have been widely documented. The enzyme that catalyzes its synthesis, thromboxane A2 synthase, and the receptors that mediate its actions, thromboxane A2 receptors, are the two key components critical for the functioning of this potent autacoid. Recent molecular biological studies have revealed the structure-function relationship and gene organizations of these proteins as well as genetic and epigenetic factors modulating their gene expression. Future investigation should shed light on detailed molecular signaling events specifying thromboxane A2 actions, and the genetic underpinning of the enzyme and the receptors in health and disease.
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Affiliation(s)
- R F Shen
- Department of Obstetrics, Gynecology, and Reproductive Sciences and Center for the Genetics of Asthma and Other Complex Diseases, University of Maryland School of Medicine, Baltimore 21201, USA.
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Zhang L, Xiao H, Schultz RA, Shen RF. Genomic organization, chromosomal localization, and expression of the murine thromboxane synthase gene. Genomics 1997; 45:519-28. [PMID: 9367676 DOI: 10.1006/geno.1997.4982] [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: 02/05/2023]
Abstract
Thromboxane synthase (TS) is a membrane-bound cytochrome P450 enzyme catalyzing the synthesis of TxA2, a potent modulator of vascular smooth muscle contraction and platelet aggregation. TS plays an important role in hemostasis and may be intimately involved in the etiology of cardiovascular, renal, and immune diseases. Restriction enzyme mapping, subcloning, and DNA sequencing analysis of recombinant phage lambda and P1 clones revealed that exons encoding the 1.9-kb mouse TS mRNA are dispersed over >150 kb genomic DNA. Determination of the intron-exon splicing junctions established that the mouse TS gene (Tbxas1) is encoded by 13 exons ranging in size from 53 (exon III) to 315 bp (exon IX). Genomic Southern analysis and fluorescence in situ hybridization suggested that the gene is a single-copy gene, located on chromosome 6 near the midpoint between the centromere and the Igkappa gene. An alternatively spliced variant of the Tbxas1 transcript, lacking the exon XII-encoded sequence, has been detected in normal mouse tissues. Ribonuclease protection and 5'-RACE assays identified at least five major transcription start sites clustered within 31 bp of the Tbxas1 promoter. The 5'-most start site is not preceded by a TATA box, suggesting transcription can be initiated in a TATA-independent manner. Transfection analyses indicated that the expression of Tbxas1 is controlled by a short (70-bp) positive regulatory sequence and several upstream repressive elements. Mutational studies further demonstrated that NF-E2/AP-1 and Sp1 exerted activating and repressive, respectively, effects on the promoter. These studies provide the genetic tools and information for TS research in mice, which should expedite understanding of the genetic contribution of TS in normal physiology as well as in disease states.
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Affiliation(s)
- L Zhang
- Department of Obstetrics, University of Maryland School of Medicine, Baltimore, Maryland, 21201, USA
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13
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Lee KD, Baek SJ, Shen RF. Multiple factors regulating the expression of human thromboxane synthase gene. Biochem J 1996; 319 ( Pt 3):783-91. [PMID: 8920981 PMCID: PMC1217857 DOI: 10.1042/bj3190783] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Characterization of the 5.5 kb promoter of human thromboxane synthase (TS) gene revealed a proximal positive regulatory sequence (PPRS, -90 to -25 bp) and several distal repressive elements. The maximal promoter activity was found to reside within the first 285 bp, approximately 75% of which was contributed by the PPRS. The sequence between -365 and -665 bp exerted a strong repressive effect (approximately 55%) on reporter gene expression independent of orientation and position, consistent with properties expected for a silencer. The sequence upstream of -665 bp to -5.5 kb contains mainly repressive elements which further reduce the promoter activity by 30%. The 65 bp PPRS worked in an orientation-independent, but position-dependent, manner and could be further divided into two independent elements, PPRS1 (-90 to -50 bp) and PPRS2 (-50 to -25 bp). While similar nuclear factor(s) from different cell types interact with PPRS2, those interacting with PPRS1 exhibit cell specificity. Internal sequence deletion and oligonucleotide competition established that a binding sequence for NF-E2 in PPRS1 (-60 tgctgattcat -50) was important for enhancing TS promoter activity in HL-60 cells. The presence of NF-E2 mRNA in HL-60 cells was demonstrated by reverse-transcription PCR amplification of the cDNA and Northern blot analysis. A 9-fold transactivation of luciferase (luc) reporter gene expression had been detected when NF-E2 cDNA was co-expressed with a TS promoter/luc construct. Despite the fact that NF-E2 and the cis-elements could alter the efficiency of TS transcription, they were not sufficient for restricting cell-specific TS expression. Analysis of the methylation status at the TS promoter in several human cell lines reveals cell-specific patterns of methylation that might correlate with TS expression. Taken together, these results suggest that the expression of human TS gene is modulated by multiple factors including cis-elements, trans-activator(s), and possibly genomic methylation.
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Affiliation(s)
- K D Lee
- Department of Obstetrics and Gynecology, University of Maryland School of Medicine, Baltimore, MD USA
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Baek SJ, Lee KD, Shen RF. Genomic structure and polymorphism of the human thromboxane synthase-encoding gene. Gene 1996; 173:251-6. [PMID: 8964509 DOI: 10.1016/0378-1119(95)00881-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Thromboxane synthase (TS) is a cytochrome P-450 (CYP450) enzyme catalyzing the conversion of prostaglandin endoperoxide (PGH2) into thromboxane A2 (TxA2) which plays a crucial role in hemostasis and cardiovascular diseases. Twelve genomic clones containing the DNA encoding the human TS gene (hTS) were isolated and characterized to determine the exon/intron boundaries and restriction maps of the nearly contiguous structure of the gene. The hTS contains 13 exons spanning more than 150 kb. Its first five exons, divided by relatively large introns, spread over 100 kb, but encode less than one third of the full-length TS transcript. Southern analysis indicates that the human haploid genome contains a single copy of the TS gene. Although multiple transcription start points (tsp) are utilized, transcription of hTS is primarily TATA-independent, as determined by promoter-directed reporter gene expression in transfected cells. A dinucleotide (CA) repetitive sequence identified in the ninth intron of the gene exhibits allelic polymorphism. At least four distinctive alleles, containing from 13 to 20 copies of the CA repeats, have been detected.
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Affiliation(s)
- S J Baek
- Department of Obstetrics and Gynecology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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Wang LH, Matijevic-Aleksic N, Hsu PY, Ruan KH, Wu KK, Kulmacz RJ. Identification of thromboxane A2 synthase active site residues by molecular modeling-guided site-directed mutagenesis. J Biol Chem 1996; 271:19970-5. [PMID: 8702713 DOI: 10.1074/jbc.271.33.19970] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Human thromboxane A2 synthase (TXAS) exhibits spectral characteristics of cytochrome P450 but lacks monooxygenase activity. Its distinctive amino acid sequence makes TXAS the sole member of family 5 in the P450 superfamily. To better understand the structure-function relationship of this unusual P450, we have recently constructed a three-dimensional model for TXAS using P450BM-3 as the template (Ruan, K.-H., Milfeld, K., Kulmacz, R. J., and Wu, K. K. (1994) Protein Eng. 7, 1345-1551) and have identified a potential active site region. The catalytic roles of several putative active site residues were evaluated using selectively mutated recombinant TXAS expressed in COS-1 cells. Mutation of Ala-408 to Glu or Arg-413 to Gly led to a complete loss of enzyme activity despite expression of mutant protein levels equivalent to that of the wild-type TXAS. Mutation of Ala-408 to Gly or Leu retained the enzyme activity at levels of 30 or 40%, respectively. This suggests that Ala-408 provides a hydrophobic environment for substrate binding. Mutation of Arg-413 to Lys or Gln completely abolished the enzyme activity, indicating that this residue is essential to catalytic activity and supports its identification as an active site residue. Mutation of Arg-410 to Gly or Glu-433 to Ala resulted in >50% reduction in the enzyme activity without appreciably altering mutant protein expression, consistent with a more subtle effect of these residues on TXAS catalytic efficiency. Mutation of residues predicted to be involved in binding the heme prosthetic group, including the heme thiolate ligand Cys-480, Arg-478, Phe-127, and Asn-110, each markedly reduced the expressed protein level and abolished enzyme activity. This suggests that proper heme binding is important to synthesis or stability of recombinant TXAS. Mutation of Ile-346, which corresponds to P450cam-Thr-252, an essential amino acid involved in dioxygen bond scission, to Thr increased the enzymatic activity by 40%, suggesting that oxygen bond cleavage is not a rate-limiting step in thromboxane A2 biosynthesis. The present results from site-directed mutagenesis support the overall structure of the TXAS active site predicted by homology modeling and have allowed refinement of the position of bound substrate.
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Affiliation(s)
- L H Wang
- Department of Internal Medicine, University of Texas Medical School, Houston, Texas 77030, USA
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Hatae T, Hara S, Yokoyama C, Yabuki T, Inoue H, Ullrich V, Tanabe T. Site-directed mutagenesis of human prostacyclin synthase: Alteration of Cys441 of the Cys-pocket, and Glu347 and Arg350 of the EXXR motif. FEBS Lett 1996; 389:268-72. [PMID: 8766713 DOI: 10.1016/0014-5793(96)00600-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The possible active site Cys441 in the Cys-pocket and Glu347 and Arg350 of the EXXR motif of the human prostacyclin synthase, which catalyzes the conversion of prostaglandin H2 to prostacyclin, were subjected to site-directed mutagenesis in order to understand the role of these residues in expressing the enzymatic activity. Five expression vectors encoding the mutant enzymes with a single replacement, Cys441 Ala, Cys441 Ser, Cys441 His, Glu347 Ala and Arg350 Ala, as well as the wild-type enzyme were expressed in 293 cells. The microsomal fraction of the cells expressing the wild-type enzyme showed a specific activity of 96 nmol 6-keto-PGF1alpha/min per mg protein. All of the mutant enzymes examined showed no detectable enzyme activity, although immunoblot analysis demonstrated that levels of all the expressed mutant enzymes were similar to that of the wild-type enzyme. These results indicated that the Cys441 in the Cys-pocket, and Glu347 and Arg350 of the EXXR motif of human prostacyclin synthase are important for expressing the enzymatic activity.
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Affiliation(s)
- T Hatae
- Department of Pharmacology, National Cardiovascular Center Research Institute, Osaka, Japan
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Tanabe T, Ullrich V. Prostacyclin and thromboxane synthases. JOURNAL OF LIPID MEDIATORS AND CELL SIGNALLING 1995; 12:243-55. [PMID: 8777569 DOI: 10.1016/0929-7855(95)00031-k] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- T Tanabe
- Department of Pharmacology, National Cardiovascular Center Research Institute, Osaka, Japan
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Hara S, Miyata A, Yokoyama C, Inoue H, Brugger R, Lottspeich F, Ullrich V, Tanabe T. Isolation and molecular cloning of prostacyclin synthase from bovine endothelial cells. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)32104-x] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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19
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Kai M, Sakane F, Imai S, Wada I, Kanoh H. Molecular cloning of a diacylglycerol kinase isozyme predominantly expressed in human retina with a truncated and inactive enzyme expression in most other human cells. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)32336-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Shen RF, Zhang L, Baek SJ, Tai HH, Lee KD. The porcine thromboxane synthase-encoding cDNA: sequence, mRNA expression and enzyme production in Sf9 insect cells. Gene X 1994; 140:261-5. [PMID: 8144035 DOI: 10.1016/0378-1119(94)90555-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
A full-length cDNA encoding porcine thromboxane synthase (TS) was isolated and sequenced. The open reading frame encodes a 534-amino acid (aa) protein (M(r) 60,451) which shares more than 75% identity with TS from other species and is 30% homologous to several enzymes of the cytochrome P-450 III family. Sequence comparison among porcine (p), human (h), and murine (m) TS indicated conservation of eight Cys residues and one putative N-glycosylation site. Several highly conserved regions were identified at the near N terminus, middle and C terminus. The most divergent region lies at aa residues 290-325, within which a Lys308 residue was unique to pTS. Between aa residues 70 and 90, considerable divergence was observed in mTS. Northern analysis showed that the pTS gene was expressed as a 2.3-kb transcript primarily in lung, kidney and thymus. A high-titer recombinant (re-) baculovirus containing pTS cDNA was developed to conduct a time course study of enzyme production in Spodoptera frugiperda (Sf9) cells. TS activity was detectable in the microsomes of Sf9 cells 12-h post-infection and reached maximum by 48 h. The produced TS resembles purified pTS in catalysis, as well as inhibition by a substrate analog inhibitor.
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Affiliation(s)
- R F Shen
- Department of Obstetrics and Gynecology, University of Maryland School of Medicine, Baltimore, MD 21201
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