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Lu JZ, Muench SP, Allary M, Campbell S, Roberts CW, Mui E, McLeod RL, Rice DW, Prigge ST. Type I and type II fatty acid biosynthesis in Eimeria tenella: enoyl reductase activity and structure. Parasitology 2007; 134:1949-62. [PMID: 17697396 PMCID: PMC2801558 DOI: 10.1017/s0031182007003319] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Apicomplexan parasites of the genus Eimeria are the major causative agent of avian coccidiosis, leading to high economic losses in the poultry industry. Recent results show that Eimeria tenella harbours an apicoplast organelle, and that a key biosynthetic enzyme, enoyl reductase, is located in this organelle. In related parasites, enoyl reductase is one component of a type II fatty acid synthase (FAS) and has proven to be an attractive target for antimicrobial compounds. We cloned and expressed the mature form of E. tenella enoyl reductase (EtENR) for biochemical and structural studies. Recombinant EtENR exhibits NADH-dependent enoyl reductase activity and is inhibited by triclosan with an IC50 value of 60 nm. The crystal structure of EtENR reveals overall similarity with other ENR enzymes; however, the active site of EtENR is unoccupied, a state rarely observed in other ENR structures. Furthermore, the position of the central beta-sheet appears to block NADH binding and would require significant movement to allow NADH binding, a feature not previously seen in the ENR family. We analysed the E. tenella genomic database for orthologues of well-characterized bacterial and apicomplexan FAS enzymes and identified 6 additional genes, suggesting that E. tenella contains a type II FAS capable of synthesizing saturated, but not unsaturated, fatty acids. Interestingly, we also identified sequences that appear to encode multifunctional type I FAS enzymes, a feature also observed in Toxoplasma gondii, highlighting the similarity between these apicomplexan parasites.
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Affiliation(s)
- J. Z. Lu
- Department of Molecular Microbiology & Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
| | - S. P. Muench
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - M. Allary
- Department of Molecular Microbiology & Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
| | - S. Campbell
- Strathclyde Institute of Biomedical Sciences, University of Strathclyde, Glasgow G4 0NR, UK
| | - C. W. Roberts
- Strathclyde Institute of Biomedical Sciences, University of Strathclyde, Glasgow G4 0NR, UK
| | - E. Mui
- Department of Ophthalmology and Visual Sciences, University of Chicago, Chicago, IL 60637, USA
| | - R. L. McLeod
- Department of Ophthalmology and Visual Sciences, University of Chicago, Chicago, IL 60637, USA
- Department of Pediatrics (Infectious Diseases), and Pathology and Committees on Genetics, Molecular Medicine and Immunology and the College, University of Chicago, Chicago, IL 60637, USA
| | - D. W. Rice
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - S. T. Prigge
- Department of Molecular Microbiology & Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
- Corresponding author: Department of Molecular Microbiology & Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA. Tel: +1 443 287 4822. Fax: +1 410 955 0105.
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Muench SP, Prigge ST, McLeod R, Rafferty JB, Kirisits MJ, Roberts CW, Mui EJ, Rice DW. Studies of Toxoplasma gondii and Plasmodium falciparum enoyl acyl carrier protein reductase and implications for the development of antiparasitic agents. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2007; 63:328-38. [PMID: 17327670 PMCID: PMC2483495 DOI: 10.1107/s0907444906053625] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2006] [Accepted: 12/11/2006] [Indexed: 11/10/2022]
Abstract
Recent studies have demonstrated that submicromolar concentrations of the biocide triclosan arrest the growth of the apicomplexan parasites Plasmodium falciparum and Toxoplasma gondii and inhibit the activity of the apicomplexan enoyl acyl carrier protein reductase (ENR). The crystal structures of T. gondii and P. falciparum ENR in complex with NAD(+) and triclosan and of T. gondii ENR in an apo form have been solved to 2.6, 2.2 and 2.8 A, respectively. The structures of T. gondii ENR have revealed that, as in its bacterial and plant homologues, a loop region which flanks the active site becomes ordered upon inhibitor binding, resulting in the slow tight binding of triclosan. In addition, the T. gondii ENR-triclosan complex reveals the folding of a hydrophilic insert common to the apicomplexan family that flanks the substrate-binding domain and is disordered in all other reported apicomplexan ENR structures. Structural comparison of the apicomplexan ENR structures with their bacterial and plant counterparts has revealed that although the active sites of the parasite enzymes are broadly similar to those of their bacterial counterparts, there are a number of important differences within the drug-binding pocket that reduce the packing interactions formed with several inhibitors in the apicomplexan ENR enzymes. Together with other significant structural differences, this provides a possible explanation of the lower affinity of the parasite ENR enzyme family for aminopyridine-based inhibitors, suggesting that an effective antiparasitic agent may well be distinct from equivalent antimicrobials.
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Affiliation(s)
- Stephen P. Muench
- The Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, England
| | - Sean T. Prigge
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
| | - Rima McLeod
- Department of Ophthalmology and Visual Sciences, Paediatrics (Infectious Diseases) and Pathology and the Committees on Molecular Medicine, Genetics, Immunology and The College, The University of Chicago, Chicago, IL 60637, USA
| | - John B. Rafferty
- The Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, England
| | - Michael J. Kirisits
- Department of Ophthalmology and Visual Sciences, Paediatrics (Infectious Diseases) and Pathology and the Committees on Molecular Medicine, Genetics, Immunology and The College, The University of Chicago, Chicago, IL 60637, USA
| | - Craig W. Roberts
- Department of Immunology, University of Strathclyde, Glasgow G4 0NR, Scotland
| | - Ernest J. Mui
- Department of Ophthalmology and Visual Sciences, Paediatrics (Infectious Diseases) and Pathology and the Committees on Molecular Medicine, Genetics, Immunology and The College, The University of Chicago, Chicago, IL 60637, USA
| | - David W. Rice
- The Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, England
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53
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Liu W, Harrison DK, Chalupska D, Gornicki P, O'Donnell CC, Adkins SW, Haselkorn R, Williams RR. Single-site mutations in the carboxyltransferase domain of plastid acetyl-CoA carboxylase confer resistance to grass-specific herbicides. Proc Natl Acad Sci U S A 2007; 104:3627-32. [PMID: 17360693 PMCID: PMC1802000 DOI: 10.1073/pnas.0611572104] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Grass weed populations resistant to aryloxyphenoxypropionate (APP) and cyclohexanedione herbicides that inhibit acetyl-CoA carboxylase (ACCase; EC 6.4.1.2) represent a major problem for sustainable agriculture. We investigated the molecular basis of resistance to ACCase-inhibiting herbicides for nine wild oat (Avena sterilis ssp. ludoviciana Durieu) populations from the northern grain-growing region of Australia. Five amino acid substitutions in plastid ACCase were correlated with herbicide resistance: Ile-1,781-Leu, Trp-1,999-Cys, Trp-2,027-Cys, Ile-2,041-Asn, and Asp-2,078-Gly (numbered according to the Alopecurus myosuroides plastid ACCase). An allele-specific PCR test was designed to determine the prevalence of these five mutations in wild oat populations suspected of harboring ACCase-related resistance with the result that, in most but not all cases, plant resistance was correlated with one (and only one) of the five mutations. We then showed, using a yeast gene-replacement system, that these single-site mutations also confer herbicide resistance to wheat plastid ACCase: Ile-1,781-Leu and Asp-2,078-Gly confer resistance to APPs and cyclohexanediones, Trp-2,027-Cys and Ile-2,041-Asn confer resistance to APPs, and Trp-1,999-Cys confers resistance only to fenoxaprop. These mutations are very likely to confer resistance to any grass weed species under selection imposed by the extensive agricultural use of the herbicides.
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Affiliation(s)
- Wenjie Liu
- *Agricultural Molecular Biotechnology Laboratory, School of Agronomy and Horticulture, University of Queensland, Gatton 4343, Queensland, Australia
| | - Dion K. Harrison
- *Agricultural Molecular Biotechnology Laboratory, School of Agronomy and Horticulture, University of Queensland, Gatton 4343, Queensland, Australia
- To whom correspondence may be addressed. E-mail: or
| | - Dominika Chalupska
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Piotr Gornicki
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Chris C. O'Donnell
- Tropical and Subtropical Weeds Research Unit, School of Land and Food Sciences, University of Queensland, Brisbane 4072, Queensland, Australia; and
| | - Steve W. Adkins
- Tropical and Subtropical Weeds Research Unit, School of Land and Food Sciences, University of Queensland, Brisbane 4072, Queensland, Australia; and
| | - Robert Haselkorn
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
- To whom correspondence may be addressed. E-mail: or
| | - Richard R. Williams
- *Agricultural Molecular Biotechnology Laboratory, School of Agronomy and Horticulture, University of Queensland, Gatton 4343, Queensland, Australia
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54
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Müller S, Kappes B. Vitamin and cofactor biosynthesis pathways in Plasmodium and other apicomplexan parasites. Trends Parasitol 2007; 23:112-21. [PMID: 17276140 PMCID: PMC2330093 DOI: 10.1016/j.pt.2007.01.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2006] [Revised: 12/13/2006] [Accepted: 01/18/2007] [Indexed: 10/23/2022]
Abstract
Vitamins are essential components of the human diet. By contrast, the malaria parasite Plasmodium falciparum and related apicomplexan parasites synthesize certain vitamins de novo, either completely or in parts. The various biosynthesis pathways are specific to different apicomplexan parasites and emphasize the distinct requirements of these parasites for nutrients and growth factors. The absence of vitamin biosynthesis in humans implies that inhibition of the parasite pathways might be a way to interfere specifically with parasite development. However, the roles of biosynthesis and uptake of vitamins in the regulation of vitamin homeostasis in parasites needs to be established first. In this article, the procurement of vitamins B(1), B(5) and B(6) by Plasmodium and other apicomplexan parasites is discussed.
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Affiliation(s)
- Sylke Müller
- University of Glasgow, Glasgow Biomedical Research Centre, Division of Infection and Immunity, Wellcome Centre for Molecular Parasitology, 120 University Place, Glasgow G12 8TA, UK.
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55
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Stelter K, El-Sayed NM, Seeber F. The Expression of a Plant-type Ferredoxin Redox System provides Molecular Evidence for a Plastid in the Early Dinoflagellate Perkinsus marinus. Protist 2007; 158:119-30. [PMID: 17123864 DOI: 10.1016/j.protis.2006.09.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2006] [Accepted: 09/29/2006] [Indexed: 11/18/2022]
Abstract
Perkinsus marinus is a parasitic protozoan with a phylogenetic positioning between Apicomplexa and dinoflagellates. It is thus of interest for reconstructing the early evolution of eukaryotes, especially with regard to the acquisition of secondary plastids in these organisms. It is also an important pathogen of oysters, and the definition of parasite-specific metabolic pathways would be beneficial for the identification of efficient treatments for infected mollusks. Although these different scientific interests have resulted in the start of a genome project for this organism, it is still unknown whether P. marinus contains a plastid or plastid-like organelle like the related dinoflagellates and Apicomplexa. Here, we show that in vitro-cultivated parasites contain transcripts of the plant-type ferredoxin and its associated reductase. Both proteins are nuclear-encoded and possess N-terminal targeting sequences similar to those characterized in dinoflagellates. Since this redox pair is exclusively found in cyanobacteria and plastid-harboring organisms its presence also in P. marinus is highly indicative of a plastid. We also provide additional evidence for such an organelle by demonstrating pharmacological sensitivity to inhibitors of plastid-localized enzymes involved in fatty acid biosynthesis (e.g. acetyl-CoA carboxylase) and by detection of genes for three enzymes of plastid-localized isoprenoid biosynthesis (1-deoxy-D-xylulose 5-phosphate reductoisomerase, (E)-4-hydroxy-3-methyl-but-2-enyl diphosphate reductase, and (E)-4-hydroxy-3-methyl-but-2-enyl diphosphate synthase).
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Affiliation(s)
- Kathrin Stelter
- FB Biologie/Parasitologie, Philipps-Universität Marburg, 35032 Marburg, Germany
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56
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Ferguson DJP, Campbell SA, Henriquez FL, Phan L, Mui E, Richards TA, Muench SP, Allary M, Lu JZ, Prigge ST, Tomley F, Shirley MW, Rice DW, McLeod R, Roberts CW. Enzymes of type II fatty acid synthesis and apicoplast differentiation and division in Eimeria tenella. Int J Parasitol 2006; 37:33-51. [PMID: 17112527 PMCID: PMC2803676 DOI: 10.1016/j.ijpara.2006.10.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2006] [Revised: 09/26/2006] [Accepted: 10/03/2006] [Indexed: 11/16/2022]
Abstract
Apicomplexan parasites, Eimeria tenella, Plasmodium spp. and Toxoplasma gondii, possess a homologous plastid-like organelle termed the apicoplast, derived from the endosymbiotic enslavement of a photosynthetic alga. However, currently no eimerian nuclear encoded apicoplast targeted proteins have been identified, unlike in Plasmodium spp. and T. gondii. In this study, we demonstrate that nuclear encoded enoyl reductase of E. tenella (EtENR) has a predicted N-terminal bipartite transit sequence, typical of apicoplast-targeted proteins. Using a combination of immunocytochemistry and EM we demonstrate that this fatty acid biosynthesis protein is located in the apicoplast of E. tenella. Using the EtENR as a tool to mark apicoplast development during the Eimeria lifecycle, we demonstrate that nuclear and apicoplast division appear to be independent events, both organelles dividing prior to daughter cell formation, with each daughter cell possessing one to four apicoplasts. We believe this is the first report of multiple apicoplasts present in the infectious stage of an apicomplexan parasite. Furthermore, the microgametes lacked an identifiable apicoplast consistent with maternal inheritance via the macrogamete. It was found that the size of the organelle and the abundance of EtENR varied with developmental stage of the E. tenella lifecycle. The high levels of EtENR protein observed during asexual development and macrogametogony is potentially associated with the increased synthesis of fatty acids required for the rapid formation of numerous merozoites and for the extracellular development and survival of the oocyst. Taken together the data demonstrate that the E. tenella apicoplast participates in type II fatty acid biosynthesis with increased expression of ENR during parasite growth. Apicoplast division results in the simultaneous formation of multiple fragments. The division mechanism is unknown, but is independent of nuclear division and occurs prior to daughter formation.
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Affiliation(s)
- D J P Ferguson
- Nuffield Department of Pathology, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK.
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57
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Abstract
Determined efforts are being made to explore the non-photosynthetic plastid organelle of Plasmodium falciparum as a target for drug development. Certain antibiotics that block organellar protein synthesis are already in clinical use as antimalarials. However, all the indications are that these should be used only in combination with conventional antimalarials. The use of antibiotics such as doxycycline and clindamycin may reduce the development of drug resistant parasites and such means to avoid drug resistance should be explored hand-in-hand with drug development. Genomic information predicts that fatty acid type II (FAS II) and isoprenoid biosynthetic pathways are localized to the plastid. However, clinical trials with fosmidomycin (a specific inhibitor of DOXP reductase in the non-mevalonate pathway for isoprenoids) suggest it too should only be used in drug combinations. Prospects for more potent antimalarial compounds have emerged from studies of several of the enzymes involved in the FAS II pathway. Lead antibiotics such as thiolactomycin (an inhibitor of beta-ketoacyl-ACP synthase) and triclosan (a specific inhibitor of enoyl-ACP reductase) have led to structurally similar, active compounds that rapidly kill ring- and trophozoite-stage parasites. The FAS II pathway is of particular interest to the pharma-industry.
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Affiliation(s)
- S Sato
- National Institute for Medical Research, Mill Hill, London NW7 1AA, UK.
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58
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Bisanz C, Bastien O, Grando D, Jouhet J, Maréchal E, Cesbron-Delauw MF. Toxoplasma gondii acyl-lipid metabolism: de novo synthesis from apicoplast-generated fatty acids versus scavenging of host cell precursors. Biochem J 2006; 394:197-205. [PMID: 16246004 PMCID: PMC1386017 DOI: 10.1042/bj20050609] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2005] [Revised: 09/23/2005] [Accepted: 10/24/2005] [Indexed: 02/04/2023]
Abstract
Toxoplasma gondii is an obligate intracellular parasite that contains a relic plastid, called the apicoplast, deriving from a secondary endosymbiosis with an ancestral alga. Metabolic labelling experiments using [14C]acetate led to a substantial production of numerous glycero- and sphingo-lipid classes in extracellular tachyzoites. Syntheses of all these lipids were affected by the herbicide haloxyfop, demonstrating that their de novo syntheses necessarily required a functional apicoplast fatty acid synthase II. The complex metabolic profiles obtained and a census of glycerolipid metabolism gene candidates indicate that synthesis is probably scattered in the apicoplast membranes [possibly for PA (phosphatidic acid), DGDG (digalactosyldiacylglycerol) and PG (phosphatidylglycerol)], the endoplasmic reticulum (for major phospholipid classes and ceramides) and mitochondria (for PA, PG and cardiolipid). Based on a bioinformatic analysis, it is proposed that apicoplast produced acyl-ACP (where ACP is acyl-carrier protein) is transferred to glycerol-3-phosphate for apicoplast glycerolipid synthesis. Acyl-ACP is also probably transported outside the apicoplast stroma and irreversibly converted into acyl-CoA. In the endoplasmic reticulum, acyl-CoA may not be transferred to a three-carbon backbone by an enzyme similar to the cytosolic plant glycerol-3-phosphate acyltransferase, but rather by a dual glycerol-3-phosphate/dihydroxyacetone-3-phosphate acyltransferase like in animal and yeast cells. We further showed that intracellular parasites could also synthesize most of their lipids from scavenged host cell precursors. The observed appearance of glycerolipids specific to either the de novo pathway in extracellular parasites (unknown glycerolipid 1 and the plant like DGDG), or the intracellular stages (unknown glycerolipid 8), may explain the necessary coexistence of both de novo parasitic acyl-lipid synthesis and recycling of host cell compounds.
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Key Words
- acyl-lipid metabolism
- apicoplast
- fatty acid synthesis
- glycerol-3-phosphate
- toxoplasma gondii
- type ii fatty acid synthase (fas ii)
- acc, acetyl-coa carboxylase
- acp, acyl-carrier protein
- ans, 8-anilinonaphthalene-1-sulphonic acid
- bodipy®, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene
- dag, diacylglycerol
- dgdg, digalactosyldiacylglycerol
- dpg, diphosphatidylglycerol
- 2d-tlc, two-dimensional tlc
- ecl, enhanced chemiluminescence
- fa, fatty acid
- fas ii, type ii fa synthase
- fop, aryloxyphenoxypropionate herbicide
- glccer, glycosylcerebroside
- hff, human foreskin fibroblast
- hstfr, human transferrin receptor
- if, immunofluorescence
- laccer, lactosylcerebroside
- mab, monoclonal antibody
- mgdg, monogalactosyldiacylglycerol
- nefa, non-esterified fa
- pa, phosphatidic acid
- pc, phosphatidylcholine
- pe, phosphatidylethanolamine
- pg, phosphatidylglycerol
- pi, phosphatidylinositol
- ps, phosphatidylserine
- pv, parasitophorous vacuole
- sqdg, sulphoquinovosyldiacylglycerol
- trihexcer, globotriosylcerebroside
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Affiliation(s)
- Cordelia Bisanz
- Laboratoire Adaptation et Pathogénie des Micro-organismes, UMR 5163, CNRS-UJF, Grenoble, France.
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Ferguson DJP, Henriquez FL, Kirisits MJ, Muench SP, Prigge ST, Rice DW, Roberts CW, McLeod RL. Maternal inheritance and stage-specific variation of the apicoplast in Toxoplasma gondii during development in the intermediate and definitive host. EUKARYOTIC CELL 2005; 4:814-26. [PMID: 15821140 PMCID: PMC1087807 DOI: 10.1128/ec.4.4.814-826.2005] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The structure and location of Toxoplasma gondii apicoplasts were examined in intermediate and definitive hosts and shown to vary in a stage-specific manner. Immunocytochemistry and electron microscopy studies were used to identify changes in the morphology of apicoplasts and in their enoyl reductase (ENR) content during asexual and sexual development. Apicoplasts in tachyzoites were small, multimembraned organelles anterior to nuclei that divided and segregated with the nuclei during endodyogeny. In nonproliferating bradyzoites within mature tissue cysts (1 to 24 months), apicoplasts had high levels of ENR. During coccidian development, asexual multiplication (endopolygeny), resulting in simultaneous formation of up to 30 daughters (merozoites), involved an initial growth phase associated with repeated nuclear divisions during which apicoplasts appeared as single, elongated, branched structures with increased levels of ENR. At initiation of merozoite formation, enlarged apicoplasts divided simultaneously, with constrictions, into portions that segregated to developing daughters. In sexual stages, apicoplast division did not occur during microgametogony, and apicoplasts were absent from the microgametes that were formed. In contrast, during macrogametogony, the apicoplast appeared as a large, branched, perinuclear structure that had very high levels of ENR in the absence of nuclear division. Marked increases in the size of apicoplasts and levels of ENR may be related to requirements of the macrogametocytes to synthesize and store all components necessary for oocyst formation and subsequent extracellular sporulation. Thus, it is shown that apicoplasts are present and contain ENR in all T. gondii life cycle stages except microgametes, which will result in maternal inheritance of the organelle.
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Affiliation(s)
- David J P Ferguson
- Department of Pathology, University of Oxford, John Radcliffe Hospital, United Kingdom
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60
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Ramya TNC, Surolia N, Surolia A. Is the fatty acid synthesis pathway a good target for anti-malarial therapy? IUBMB Life 2005; 57:371-3. [PMID: 16036622 DOI: 10.1080/15216540500091460] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- T N C Ramya
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
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61
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Wiesner J, Seeber F. The plastid-derived organelle ofprotozoan human parasites asa target of established and emerging drugs. Expert Opin Ther Targets 2005; 9:23-44. [PMID: 15757480 DOI: 10.1517/14728222.9.1.23] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Human diseases like malaria, toxoplasmosis or cryptosporidiosis are caused by intracellular protozoan parasites of the phylum Apicomplexa and are still a major health problem worldwide. In the case of Plasmodium falciparum, the causative agent of tropical malaria, resistance against previously highly effective drugs is widespread and requires the continued development of new and affordable drugs. Most apicomplexan parasites possess a single plastid-derived organelle called apicoplast, which offers the great opportunity to tailor highly specific inhibitors against vital metabolic pathways resident in this compartment. This is due to the fact that several of these pathways, being of bacterial or algal origin, are absent in the mammalian host. In fact, the targets of several antibiotics already in use for years against some of these diseases can now be traced to the apicoplast and by knowing the molecular entities which are affected by these substances, improved drugs or drug combinations can be envisaged to emerge from this knowledge. Likewise, apicoplast-resident pathways like fatty acid or isoprenoid biosynthesis have already been proven to be the likely targets of the next drug generation. In this review the current knowledge on the different targets and available inhibitors (both established and experimental) will be summarised and an overview of the clinical efficacy of drugs that inhibit functions in the apicoplast and which have been tested in humans so far will be given.
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Affiliation(s)
- Jochen Wiesner
- Justus-Liebig-Universität Giessen, Biochemisches Institut, Friedrichstr. 24, D-35392 Giessen, Germany
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62
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Ralph SA, van Dooren GG, Waller RF, Crawford MJ, Fraunholz MJ, Foth BJ, Tonkin CJ, Roos DS, McFadden GI. Tropical infectious diseases: metabolic maps and functions of the Plasmodium falciparum apicoplast. Nat Rev Microbiol 2005; 2:203-16. [PMID: 15083156 DOI: 10.1038/nrmicro843] [Citation(s) in RCA: 432] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Stuart A Ralph
- Institut Pasteur, Biology of Host-Parasite Interactions, 25 Rue du Docteur Roux, 75724, Paris, Cedex 15, France
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63
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Abstract
Considerable work still needs to be done to understand more fully the basic processes going on inside the non-photosynthetic plastid organelle of Plasmodium spp., the causative agent of malaria. Following an explosion of genomic and transcriptional information in recent years, research workers are still analysing these data looking for new material relevant to the plastid. Several metabolic and housekeeping functions based on bacterial biochemistry have been elucidated and this has given impetus to finding lead inhibitors based on established anti-microbials. Structural investigations of plastid-associated enzymes identified as potential targets have begun. This review gives a perspective on the research to date and hopes to emphasize that a practical outcome for the clinic should be an important focus of future efforts. Malaria parasites have become resistant to front-line anti-malarials that are widely used and were formerly dependable. This has become a worrying problem in many regions where malaria is endemic. The time lag between hunting for new inhibitors and their application as pharmaceuticals is so long and costly that a steady stream of new ventures has to be undertaken to give a reasonable chance of finding affordable and appropriate anti-malarials for the future. Attempts to find inhibitors of the plastid organelle of the malaria parasite should be intensified in such programmes.
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Affiliation(s)
- R J M Iain Wilson
- National Institute for Medical Research, Mill Hill, London, NW7 1AA, UK.
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64
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Xu P, Widmer G, Wang Y, Ozaki LS, Alves JM, Serrano MG, Puiu D, Manque P, Akiyoshi D, Mackey AJ, Pearson WR, Dear PH, Bankier AT, Peterson DL, Abrahamsen MS, Kapur V, Tzipori S, Buck GA. The genome of Cryptosporidium hominis. Nature 2004; 431:1107-12. [PMID: 15510150 DOI: 10.1038/nature02977] [Citation(s) in RCA: 385] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2004] [Accepted: 08/06/2004] [Indexed: 11/09/2022]
Abstract
Cryptosporidium species cause acute gastroenteritis and diarrhoea worldwide. They are members of the Apicomplexa--protozoan pathogens that invade host cells by using a specialized apical complex and are usually transmitted by an invertebrate vector or intermediate host. In contrast to other Apicomplexans, Cryptosporidium is transmitted by ingestion of oocysts and completes its life cycle in a single host. No therapy is available, and control focuses on eliminating oocysts in water supplies. Two species, C. hominis and C. parvum, which differ in host range, genotype and pathogenicity, are most relevant to humans. C. hominis is restricted to humans, whereas C. parvum also infects other mammals. Here we describe the eight-chromosome approximately 9.2-million-base genome of C. hominis. The complement of C. hominis protein-coding genes shows a striking concordance with the requirements imposed by the environmental niches the parasite inhabits. Energy metabolism is largely from glycolysis. Both aerobic and anaerobic metabolisms are available, the former requiring an alternative electron transport system in a simplified mitochondrion. Biosynthesis capabilities are limited, explaining an extensive array of transporters. Evidence of an apicoplast is absent, but genes associated with apical complex organelles are present. C. hominis and C. parvum exhibit very similar gene complements, and phenotypic differences between these parasites must be due to subtle sequence divergence.
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Affiliation(s)
- Ping Xu
- Center for the Study of Biological Complexity, Virginia Commonwealth University, Richmond, Virginia 23284-2030, USA
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65
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Surolia A, Ramya T, Ramya V, Surolia N. 'FAS't inhibition of malaria. Biochem J 2004; 383:401-12. [PMID: 15315475 PMCID: PMC1133732 DOI: 10.1042/bj20041051] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2004] [Revised: 08/04/2004] [Accepted: 08/18/2004] [Indexed: 01/29/2023]
Abstract
Malaria, a tropical disease caused by Plasmodium sp., has been haunting mankind for ages. Unsuccessful attempts to develop a vaccine, the emergence of resistance against the existing drugs and the increasing mortality rate all call for immediate strategies to treat it. Intense attempts are underway to develop potent analogues of the current antimalarials, as well as a search for novel drug targets in the parasite. The indispensability of apicoplast (plastid) to the survival of the parasite has attracted a lot of attention in the recent past. The present review describes the origin and the essentiality of this relict organelle to the parasite. We also show that among the apicoplast specific pathways, the fatty acid biosynthesis system is an attractive target, because its inhibition decimates the parasite swiftly unlike the 'delayed death' phenotype exhibited by the inhibition of the other apicoplast processes. As the enzymes of the fatty acid biosynthesis system are present as discrete entities, unlike those of the host, they are amenable to inhibition without impairing the operation of the host-specific pathway. The present review describes the role of these enzymes, the status of their molecular characterization and the current advancements in the area of developing inhibitors against each of the enzymes of the pathway.
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Key Words
- antimalarial
- apicoplast
- fatty acid biosynthesis pathway
- malaria
- plasmodium falciparum
- triclosan
- acat, acyl-coa:acp transacylase
- acc, acetyl-coa carboxylase
- acp, acyl carrier protein
- cer, cerulenin
- fas, fatty acid synthase
- inh, isoniazid
- inha, enoyl-acp reductase of mycobacterium tuberculosis
- kas, β-oxoacyl-acp synthase (β-ketoacyl-acp synthase)
- mcat, malonyl-coa:acp transacylase
- orf, open reading frame
- pdh, pyruvate dehydrogenase
- pep, phosphoenolpyruvate
- pf, plasmodium falciparum
- tlm, thiolactomycin
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Affiliation(s)
- Avadhesha Surolia
- *Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
| | - T. N. C. Ramya
- *Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
| | - V. Ramya
- *Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
| | - Namita Surolia
- †Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India
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66
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Abstract
Cryptosporidium parvum is one of the apicomplexans that can cause severe diarrhea in humans and animals. The slow development of anti-cryptosporidiosis chemotherapy is primarily due to the poor understanding on the basic metabolic pathways in this parasite. Many well-defined or promising drug targets found in other apicomplexans are either absent or highly divergent in C. parvum. The recently discovered apicoplast and its associated Type II fatty acid synthetic enzymes in Plasmodium, Toxoplasma, and Eimeria apicomplexans are absent in C. parvum, suggesting this parasite is unable to synthesize fatty acids de novo. However, C. parvum possesses a giant Type I fatty acid synthase (CpFAS1) that makes very long chain fatty acids using mediate or long chain fatty acids as precursors. Cryptosporidium also contains a Type I polyketide synthase (CpPKS1) that is probably involved in the production of unknown polyketide(s) from a fatty acid precursor. In addition to CpFAS1 and CpPKS1, a number of other enzymes involved in fatty acid metabolism have also been identified. These include a long chain fatty acyl elongase (LCE), a cytosolic acetyl-CoA carboxylase (ACCase), three acyl-CoA synthases (ACS), and an unusual "long-type" acyl-CoA binding protein (ACBP), which allows us to hypothetically reconstruct the highly streamlined fatty acid metabolism in this parasite. However, C. parvum lacks enzymes for the oxidation of fatty acids, indicating that fatty acids are not an energy source for this parasite. Since fatty acids are essential components of all biomembranes, molecular and functional studies on these critical enzymes would not only deepen our understanding on the basic metabolism in the parasites, but also point new directions for the drug discovery against C. parvum and other apicomplexan-based diseases.
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Affiliation(s)
- Guan Zhu
- Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, 4467 TAMU, College Station, Texas 77843-4467, USA.
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67
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Zhang H, Tweel B, Tong L. Molecular basis for the inhibition of the carboxyltransferase domain of acetyl-coenzyme-A carboxylase by haloxyfop and diclofop. Proc Natl Acad Sci U S A 2004; 101:5910-5. [PMID: 15079078 PMCID: PMC395897 DOI: 10.1073/pnas.0400891101] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Acetyl-CoA carboxylases (ACCs) are crucial for the metabolism of fatty acids, making these enzymes important targets for the development of therapeutics against obesity, diabetes, and other diseases. The carboxyltransferase (CT) domain of ACC is the site of action of commercial herbicides, such as haloxyfop, diclofop, and sethoxydim. We have determined the crystal structures at up to 2.5-A resolution of the CT domain of yeast ACC in complex with the herbicide haloxyfop or diclofop. The inhibitors are bound in the active site, at the interface of the dimer of the CT domain. Unexpectedly, inhibitor binding requires large conformational changes for several residues in this interface, which create a highly conserved hydrophobic pocket that extends deeply into the core of the dimer. Two residues that affect herbicide sensitivity are located in this binding site, and mutation of these residues disrupts the structure of the domain. Other residues in the binding site are strictly conserved among the CT domains.
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Affiliation(s)
- Hailong Zhang
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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68
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Samuel BU, Hearn B, Mack D, Wender P, Rothbard J, Kirisits MJ, Mui E, Wernimont S, Roberts CW, Muench SP, Rice DW, Prigge ST, Law AB, McLeod R. Delivery of antimicrobials into parasites. Proc Natl Acad Sci U S A 2003; 100:14281-6. [PMID: 14623959 PMCID: PMC283583 DOI: 10.1073/pnas.2436169100] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To eliminate apicomplexan parasites, inhibitory compounds must cross host cell, parasitophorous vacuole, and parasite membranes and cyst walls, making delivery challenging. Here, we show that short oligomers of arginine enter Toxoplasma gondii tachyzoites and encysted bradyzoites. Triclosan, which inhibits enoyl-ACP reductase (ENR), conjugated to arginine oligomers enters extracellular tachyzoites, host cells, tachyzoites inside parasitophorous vacuoles within host cells, extracellular bradyzoites, and bradyzoites within cysts. We identify, clone, and sequence T. gondii enr and produce and characterize enzymatically active, recombinant ENR. This enzyme has the requisite amino acids to bind triclosan. Triclosan released after conjugation to octaarginine via a readily hydrolyzable ester linkage inhibits ENR activity, tachyzoites in vitro, and tachyzoites in mice. Delivery of an inhibitor to a microorganism via conjugation to octaarginine provides an approach to transporting antimicrobials and other small molecules to sequestered parasites, a model system to characterize transport across multiple membrane barriers and structures, a widely applicable paradigm for treatment of active and encysted apicomplexan and other infections, and a generic proof of principle for a mechanism of medicine delivery.
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Affiliation(s)
- B U Samuel
- Department of Visual Sciences, University of Chicago, 5841 South Maryland, AMB S-208, Chicago, IL 60637, USA
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69
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Gornicki P. Apicoplast fatty acid biosynthesis as a target for medical intervention in apicomplexan parasites. Int J Parasitol 2003; 33:885-96. [PMID: 12906873 DOI: 10.1016/s0020-7519(03)00133-4] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
New chemotherapies for human and animal apicomplexan infections are needed as a component of future strategies to deal with these diseases. An extensive search for new treatments exploring the unique developmental physiology, metabolism and molecular structures of Apicomplexa is under way. The description of the full complement of about 5,300 Plasmodium falciparum genes and fast growing sequence databases for other Apicomplexa allow reconstruction of metabolic pathways of these parasites and thus accelerate identification and biochemical analysis of potential targets. The apicoplast de novo fatty acid biosynthetic pathway shows great potential as a target for small-molecule inhibitors in a stand-alone or combination chemotherapy. Three enzymatic activities, acetyl-CoA carboxylase, beta-ketoacyl-ACP synthase and enoyl-ACP reductase, respond to inhibitors previously identified for bacteria and plants, and deserve to be explored in depth. In this connection, screening systems have been established to seek more potent and specific antiparasitic compounds that are harmless to the host. To this end the interconnections of fatty acid biosynthesis in Apicomplexa with other metabolic and cellular processes must be investigated.
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Affiliation(s)
- Piotr Gornicki
- Department of Molecular Genetics and Cell Biology, University of Chicago, 920 East 58th Street, Chicago IL 60637, USA.
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70
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Délye C, Zhang XQ, Chalopin C, Michel S, Powles SB. An isoleucine residue within the carboxyl-transferase domain of multidomain acetyl-coenzyme A carboxylase is a major determinant of sensitivity to aryloxyphenoxypropionate but not to cyclohexanedione inhibitors. PLANT PHYSIOLOGY 2003; 132:1716-23. [PMID: 12857850 PMCID: PMC167108 DOI: 10.1104/pp.103.021139] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2003] [Revised: 02/17/2003] [Accepted: 03/09/2003] [Indexed: 05/19/2023]
Abstract
A 3,300-bp DNA fragment encoding the carboxyl-transferase domain of the multidomain, chloroplastic acetyl-coenzyme A carboxylase (ACCase) was sequenced in aryloxyphenoxypropionate (APP)-resistant and -sensitive Alopecurus myosuroides (Huds.). No resistant plant contained an Ile-1,781-Leu substitution, previously shown to confer resistance to APPs and cyclohexanediones (CHDs). Instead, an Ile-2,041-Asn substitution was found in resistant plants. Phylogenetic analysis of the sequences revealed that Asn-2,041 ACCase alleles derived from several distinct origins. Allele-specific polymerase chain reaction associated the presence of Asn-2,041 with seedling resistance to APPs but not to CHDs. ACCase enzyme assays confirmed that Asn-2,041 ACCase activity was moderately resistant to CHDs but highly resistant to APPs. Thus, the Ile-2,041-Asn substitution, which is located outside a domain previously shown to control sensitivity to APPs and CHDs in wheat (Triticum aestivum), is a direct cause of resistance to APPs only. In known multidomain ACCases, the position corresponding to the Ile/Asn-2,041 residue in A. myosuroides is occupied by an Ile or a Val residue. In Lolium rigidum (Gaud.), we found Ile-Asn and Ile-Val substitutions. The Ile-Val change did not confer resistance to the APP clodinafop, whereas the Ile-Asn change did. The position and the particular substitution at this position are of importance for sensitivity to APPs.
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Affiliation(s)
- Christophe Délye
- Institut National de la Recherche Agronomique, Unité de Malherbologie et Agronomie, B.P. 86510, F-21065 Dijon cedex, France.
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71
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Abstract
Parasitic protozoa are surrounded by membrane structures that have a different lipid and protein composition relative to membranes of the host. The parasite membranes are essential structurally and also for parasite specific processes, like host cell invasion, nutrient acquisition or protection against the host immune system. Furthermore, intracellular parasites can modulate membranes of their host, and trafficking of membrane components occurs between host membranes and those of the intracellular parasite. Phospholipids are major membrane components and, although many parasites scavenge these phospholipids from their host, most parasites also synthesise phospholipids de novo, or modify a large part of the scavenged phospholipids. It was recently shown that some parasites like Plasmodium have unique phospholipid metabolic pathways. This review will focus on new developments in research on phospholipid metabolism of parasitic protozoa in relation to parasite-specific membrane structures and function, as well as on several targets for interference with the parasite phospholipid metabolism with a view to developing new anti-parasitic drugs.
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Affiliation(s)
- Henri J Vial
- Dynamique Moléculaire des Interactions Membranaires, CNRS UMR 5539, cc107, Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier, France.
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72
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Roberts CW, McLeod R, Rice DW, Ginger M, Chance ML, Goad LJ. Fatty acid and sterol metabolism: potential antimicrobial targets in apicomplexan and trypanosomatid parasitic protozoa. Mol Biochem Parasitol 2003; 126:129-42. [PMID: 12615312 DOI: 10.1016/s0166-6851(02)00280-3] [Citation(s) in RCA: 210] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Current treatments for diseases caused by apicomplexan and trypanosomatid parasites are inadequate due to toxicity, the development of drug resistance and an inability to eliminate all life cycle stages of these parasites from the host. New therapeutics agents are urgently required. It has recently been demonstrated that type II fatty acid biosynthesis occurs in the plastid of Plasmodium falciparum and Toxoplasma gondii and inhibitors of this pathway such as triclosan and thiolactomycin restrict their growth. Furthermore, Trypanosoma brucei has recently been demonstrated to use type II fatty acid biosynthesis for myristate synthesis and to be susceptible to thiolactomycin. As this pathway is absent from mammals, it may provide an excellent target for novel antimicrobial agents to combat these diverse parasites. Leishmania and Trypanosoma parasites produce ergosterol-related sterols by a biosynthetic pathway similar to that operating in pathogenic fungi and their growth is susceptible to sterol biosynthesis inhibitors. Thus, inhibition of squalene 2,3-epoxidase by terbinafine, 14alpha-methylsterol 14-demethylase by azole and triazole compounds and delta(24)-sterol methyl transferase by azasterols all cause a depletion of normal sterols and an accumulation of abnormal amounts of sterol precursors with cytostatic or cytoxic consequences. However, Leishmania parasites can survive with greatly altered sterol profiles induced by continuous treatment with low concentrations of some inhibitors and they also have some ability to utilise and metabolise host sterol. These properties may permit the parasites to evade treatment with sterol biosynthesis inhibitors in some clinical situations and need to be taken into account in the design of future drugs.
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Affiliation(s)
- C W Roberts
- Department of Immunology, Strathclyde Institute for Biomedical Sciences, University of Strathclyde, Glasgow G4 ONR, Scotland, UK.
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73
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Waller RF, Ralph SA, Reed MB, Su V, Douglas JD, Minnikin DE, Cowman AF, Besra GS, McFadden GI. A type II pathway for fatty acid biosynthesis presents drug targets in Plasmodium falciparum. Antimicrob Agents Chemother 2003; 47:297-301. [PMID: 12499205 PMCID: PMC148988 DOI: 10.1128/aac.47.1.297-301.2003] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
It has long been held that the malaria parasite, Plasmodium sp., is incapable of de novo fatty acid synthesis. This view has recently been overturned with the emergence of data for the presence of a fatty acid biosynthetic pathway in the relict plastid of P. falciparum (known as the apicoplast). This pathway represents the type II pathway common to plant chloroplasts and bacteria but distinct from the type I pathway of animals including humans. Specific inhibitors of the type II pathway, thiolactomycin and triclosan, have been reported to target this Plasmodium pathway. Here we report further inhibitors of the plastid-based pathway that inhibit Plasmodium parasites. These include several analogues of thiolactomycin, two with sixfold-greater efficacy than thiolactomycin. We also report that parasites respond very rapidly to such inhibitors and that the greatest sensitivity is seen in ring-stage parasites. This study substantiates the importance of fatty acid synthesis for blood-stage parasite survival and shows that this pathway provides scope for the development of novel antimalarial drugs.
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Affiliation(s)
- Ross F Waller
- School of Biochemistry and Molecular Biology, University of Melbourne, Melbourne, Victoria 3010, Australia.
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74
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Simpson CL, Stern DB. The treasure trove of algal chloroplast genomes. Surprises in architecture and gene content, and their functional implications. PLANT PHYSIOLOGY 2002; 129:957-66. [PMID: 12114552 PMCID: PMC1540241 DOI: 10.1104/pp.010908] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Affiliation(s)
- Clare L Simpson
- Boyce Thompson Institute for Plant Research, Cornell University, Tower Road, Ithaca, New York 14853, USA
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75
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Jelenska J, Sirikhachornkit A, Haselkorn R, Gornicki P. The carboxyltransferase activity of the apicoplast acetyl-CoA carboxylase of Toxoplasma gondii is the target of aryloxyphenoxypropionate inhibitors. J Biol Chem 2002; 277:23208-15. [PMID: 11980900 DOI: 10.1074/jbc.m200455200] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Inhibition of growth of the apicomplexan parasite Toxoplasma gondii by aryloxyphenoxypropionate herbicides has been correlated with the inhibition of its acetyl-CoA carboxylase (ACC) by these compounds. Here, full-length and C-terminal fragments of T. gondii apicoplast ACC as well as C-terminal fragments of the cytosolic ACC were expressed in Escherichia coli. The recombinant proteins that were soluble showed the expected enzymatic activities. Yeast gene-replacement strains depending for growth on the expressed T. gondii ACC were derived by complementation of a yeast ACC1 null mutation. In vitro and in vivo tests with aryloxyphenoxypropionates showed that the carboxyltransferase domain of the apicoplast T. gondii ACC is the target for this class of inhibitors. The cytosolic T. gondii ACC is resistant to aryloxyphenoxypropionates. Both T. gondii isozymes are resistant to cyclohexanediones, another class of inhibitors targeting the ACC of grass plastids.
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Affiliation(s)
- Joanna Jelenska
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois 60637, USA
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76
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Abstract
This review offers a snapshot of our current understanding of the origin, biology, and metabolic significance of the non-photosynthetic plastid organelle found in apicomplexan parasites. These protists are of considerable medical and veterinary importance world-wide, Plasmodium spp., the causative agent of malaria being foremost in terms of human disease. It has been estimated that approximately 8% of the genes currently recognized by the malarial genome sequencing project (now nearing completion) are of bacterial/plastid origin. The bipartite presequences directing the products of these genes back to the plastid have provided fresh evidence that secondary endosymbiosis accounts for this organelle's presence in these parasites. Mounting phylogenetic evidence has strengthened the likelihood that the plastid originated from a red algal cell. Most importantly, we now have a broad understanding of several bacterial metabolic systems confined within the boundaries of the parasite plastid. The primary ones are type II fatty acid biosynthesis and isoprenoid biosynthesis. Some aspects of heme biosynthesis also might take place there. Retention of the plastid's relict genome and its still ill-defined capacity to participate in protein synthesis might be linked to an important house-keeping process, i.e. guarding the type II fatty acid biosynthetic pathway from oxidative damage. Fascinating observations have shown the parasite plastid does not divide by constriction as in typical plants, and that plastid-less parasites fail to thrive after invading a new cell. The modes of plastid DNA replication within the phylum also have provided surprises. Besides indicating the potential of the parasite plastid for therapeutic intervention, this review exposes many gaps remaining in our knowledge of this intriguing organelle. The rapid progress being made shows no sign of slackening.
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Affiliation(s)
- R J M Iain Wilson
- National Institute for Medical Research, Mill Hill, London NW7 1AA, UK.
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77
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Abstract
Coccidia provide a rich hunting ground for drug-designers, as there are significant biochemical differences between the parasites and their hosts. Recent years have brought the discovery of the plastid and its possible metabolic machinery, characterisation of acidocalcisomes, reports on the apparent absence from some coccidia of a typical mitochondrion, and the discovery of the mannitol cycle and shikimate pathway in the parasites. Moreover, modern technologies such as genomics and proteomics are bringing new insights into the biochemistry of coccidia and highlighting possible drug targets in abundance. A major issue for would-be drug discoverers is to decide upon the targets to prioritise. This review provides an update on recent findings on how coccidia differ biochemically from vertebrates. It includes discoveries within coccidian parasites themselves but also uses findings in Plasmodium to provide an overview of biochemical features that may be characteristics of many apicomplexan parasites and so potential targets for broad-spectrum drugs.
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Affiliation(s)
- G H Coombs
- Division of Infection and Immunity, Institute of Biomedical and Life Sciences, Joseph Black Building, University of Glasgow, G12 8QQ, Glasgow, UK.
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78
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Paul KS, Jiang D, Morita YS, Englund PT. Fatty acid synthesis in African trypanosomes: a solution to the myristate mystery. Trends Parasitol 2001; 17:381-7. [PMID: 11685899 DOI: 10.1016/s1471-4922(01)01984-5] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The glycosyl phosphatidylinositol anchor of the trypanosome variant surface glycoprotein contains myristate as its sole fatty acid component. Surprisingly, there does not appear to be enough myristate in either the parasite or its host's bloodstream to sustain myristoylation of the enormous quantity of variant surface glycoprotein produced. Here, we discuss how the trypanosome solves its myristate dilemma. The parasite not only efficiently salvages and processes myristate from the bloodstream, but it also makes myristate de novo using a recently discovered specialized fatty acid synthesis system.
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Affiliation(s)
- K S Paul
- Dept Biological Chemistry, Johns Hopkins Medical School, 725 N. Wolfe Street, Baltimore, MD 21205, USA
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79
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He CY, Striepen B, Pletcher CH, Murray JM, Roos DS. Targeting and processing of nuclear-encoded apicoplast proteins in plastid segregation mutants of Toxoplasma gondii. J Biol Chem 2001; 276:28436-42. [PMID: 11319231 DOI: 10.1074/jbc.m102000200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The apicoplast is a distinctive organelle associated with apicomplexan parasites, including Plasmodium sp. (which cause malaria) and Toxoplasma gondii (the causative agent of toxoplasmosis). This unusual structure (acquired by the engulfment of an ancestral alga and retention of the algal plastid) is essential for long-term parasite survival. Similar to other endosymbiotic organelles (mitochondria, chloroplasts), the apicoplast contains proteins that are encoded in the nucleus and post-translationally imported. Translocation across the four membranes surrounding the apicoplast is mediated by an N-terminal bipartite targeting sequence. Previous studies have described a recombinant "poison" that blocks plastid segregation during mitosis, producing parasites that lack an apicoplast and siblings containing a gigantic, nonsegregating plastid. To learn more about this remarkable phenomenon, we examined the localization and processing of the protein produced by this construct. Taking advantage of the ability to isolate apicoplast segregation mutants, we also demonstrated that processing of the transit peptide of nuclear-encoded apicoplast proteins requires plastid-associated activity.
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Affiliation(s)
- C Y He
- Department of Biology, Cancer Center Flow Cytometry Shared Resource, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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80
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Zagnitko O, Jelenska J, Tevzadze G, Haselkorn R, Gornicki P. An isoleucine/leucine residue in the carboxyltransferase domain of acetyl-CoA carboxylase is critical for interaction with aryloxyphenoxypropionate and cyclohexanedione inhibitors. Proc Natl Acad Sci U S A 2001; 98:6617-22. [PMID: 11381131 PMCID: PMC34402 DOI: 10.1073/pnas.121172798] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
cDNA fragments encoding the carboxyltransferase domain of the multidomain plastid acetyl-CoA carboxylase (ACCase) from herbicide-resistant maize and from herbicide-sensitive and herbicide-resistant Lolium rigidum were cloned and sequenced. A Leu residue was found in ACCases from herbicide-resistant plants at a position occupied by Ile in all ACCases from sensitive grasses studied so far. Leu is present at the equivalent position in herbicide-resistant ACCases from other eukaryotes. Chimeric ACCases containing a 1000-aa fragment of two ACCase isozymes found in a herbicide-resistant maize were expressed in a yeast ACC1 null mutant to test herbicide sensitivity of the enzyme in vivo and in vitro. One of the enzymes was resistant/tolerant, and one was sensitive to haloxyfop and sethoxydim, rendering the gene-replacement yeast strains resistant and sensitive to these compounds, respectively. The sensitive enzyme has an Ile residue, and the resistant one has a Leu residue at the putative herbicide-binding site. Additionally, a single Ile to Leu replacement at an equivalent position changes the wheat plastid ACCase from sensitive to resistant. The effect of the opposite substitution, Leu to Ile, makes Toxoplasma gondii apicoplast ACCase resistant to haloxyfop and clodinafop. In this case, inhibition of the carboxyltransferase activity of ACCase (second half-reaction) of a large fragment of the Toxoplasma enzyme expressed in Escherichia coli was tested. The critical amino acid residue is located close to a highly conserved motif of the carboxyltransferase domain, which is probably a part of the enzyme active site, providing the basis for the activity of fop and dim herbicides.
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Affiliation(s)
- O Zagnitko
- Department of Molecular Genetics and Cell Biology, University of Chicago, 920 East 58th Street, Chicago, IL 60637, USA
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81
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Abstract
Resistance to commonly used malaria drugs is spreading and new drugs are required urgently. The recent identification of a relict chloroplast (apicoplast) in malaria and related parasites offers numerous new targets for drug therapy using well-characterized compounds. The apicoplast contains a range of metabolic pathways and housekeeping processes that differ radically to those of the host thereby presenting ideal strategies for drug therapy. Indeed, many compounds targeting these plastid pathways are antimalarial and have favourable profiles based on extensive knowledge from their use as antibacterials.
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Affiliation(s)
- S A Ralph
- Plant Cell Biology Research Centre, School of Botany, University of Melbourne, Australia
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82
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Maréchal E, Cesbron-Delauw MF. The apicoplast: a new member of the plastid family. TRENDS IN PLANT SCIENCE 2001; 6:200-205. [PMID: 11335172 DOI: 10.1016/s1360-1385(01)01921-5] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Protozoan parasites of the phylum Apicomplexa include pathogens such as Plasmodium, Toxoplasma and Cryptosporidium. They have been shown to contain a vestigial nonphotosynthetic plastid, the apicoplast, which might have arisen by secondary endosymbiosis. Little is known about the function of the apicoplast but the parasites exhibit delayed cell death when their apicoplast is impaired. The discovery of the apicoplast opens an unexpected opportunity to link current fundamental research on plant and algal plastids to the physiology of apicomplexans. For example, the apicoplast might provide new targets for innovative drugs that act as herbicides and do not affect the mammalian host.
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Affiliation(s)
- E Maréchal
- Laboratoire de Physiologie Cellulaire Végétale, UMR 5019 CNRS-CEA-Université Joseph Fourier, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
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83
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Fast NM, Kissinger JC, Roos DS, Keeling PJ. Nuclear-encoded, plastid-targeted genes suggest a single common origin for apicomplexan and dinoflagellate plastids. Mol Biol Evol 2001; 18:418-26. [PMID: 11230543 DOI: 10.1093/oxfordjournals.molbev.a003818] [Citation(s) in RCA: 267] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The phylum Apicomplexa encompasses a large number of intracellular protozoan parasites, including the causative agents of malaria (Plasmodium), toxoplasmosis (Toxoplasma), and many other human and animal diseases. Apicomplexa have recently been found to contain a relic, nonphotosynthetic plastid that has attracted considerable interest as a possible target for therapeutics. This plastid is known to have been acquired by secondary endosymbiosis, but when this occurred and from which type of alga it was acquired remain uncertain. Based on the molecular phylogeny of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes, we provide evidence that the apicomplexan plastid is homologous to plastids found in dinoflagellates-close relatives of apicomplexa that contain secondary plastids of red algal origin. Surprisingly, apicomplexan and dinoflagellate plastid-targeted GAPDH sequences were also found to be closely related to the plastid-targeted GAPDH genes of heterokonts and cryptomonads, two other groups that contain secondary plastids of red algal origin. These results address several outstanding issues: (1) apicomplexan and dinoflagellate plastids appear to be the result of a single endosymbiotic event which occurred relatively early in eukaryotic evolution, also giving rise to the plastids of heterokonts and perhaps cryptomonads; (2) apicomplexan plastids are derived from a red algal ancestor; and (3) the ancestral state of apicomplexan parasites was photosynthetic.
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Affiliation(s)
- N M Fast
- Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada.
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84
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Jelenska J, Crawford MJ, Harb OS, Zuther E, Haselkorn R, Roos DS, Gornicki P. Subcellular localization of acetyl-CoA carboxylase in the apicomplexan parasite Toxoplasma gondii. Proc Natl Acad Sci U S A 2001; 98:2723-8. [PMID: 11226307 PMCID: PMC30206 DOI: 10.1073/pnas.051629998] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Apicomplexan parasites such as Toxoplasma gondii contain a primitive plastid, the apicoplast, whose genome consists of a 35-kb circular DNA related to the plastid DNA of plants. Plants synthesize fatty acids in their plastids. The first committed step in fatty acid synthesis is catalyzed by acetyl-CoA carboxylase (ACC). This enzyme is encoded in the nucleus, synthesized in the cytosol, and transported into the plastid. In the present work, two genes encoding ACC from T. gondii were cloned and the gene structure was determined. Both ORFs encode multidomain proteins, each with an N-terminal extension, compared with the cytosolic ACCs from plants. The N-terminal extension of one isozyme, ACC1, was shown to target green fluorescent protein to the apicoplast of T. gondii. In addition, the apicoplast contains a biotinylated protein, consistent with the assertion that ACC1 is localized there. The second ACC in T. gondii appears to be cytosolic. T. gondii mitochondria also contain a biotinylated protein, probably pyruvate carboxylase. These results confirm the essential nature of the apicoplast and explain the inhibition of parasite growth in cultured cells by herbicides targeting ACC.
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Affiliation(s)
- J Jelenska
- Department of Molecular Genetics and Cell Biology, University of Chicago, 920 East 58th Street, Chicago, IL 60637, USA
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85
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McLeod R, Muench SP, Rafferty JB, Kyle DE, Mui EJ, Kirisits MJ, Mack DG, Roberts CW, Samuel BU, Lyons RE, Dorris M, Milhous WK, Rice DW. Triclosan inhibits the growth of Plasmodium falciparum and Toxoplasma gondii by inhibition of apicomplexan Fab I. Int J Parasitol 2001; 31:109-13. [PMID: 11239932 DOI: 10.1016/s0020-7519(01)00111-4] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Fab I, enoyl acyl carrier protein reductase (ENR), is an enzyme used in fatty acid synthesis. It is a single chain polypeptide in plants, bacteria, and mycobacteria, but is part of a complex polypeptide in animals and fungi. Certain other enzymes in fatty acid synthesis in apicomplexan parasites appear to have multiple forms, homologous to either a plastid, plant-like single chain enzyme or more like the animal complex polypeptide chain. We identified a plant-like Fab I in Plasmodium falciparum and modelled the structure on the Brassica napus and Escherichia coli structures, alone and complexed to triclosan (5-chloro-2-[2,4 dichlorophenoxy] phenol]), which confirmed all the requisite features of an ENR and its interactions with triclosan. Like the remarkable effect of triclosan on a wide variety of bacteria, this compound markedly inhibits growth and survival of the apicomplexan parasites P. falciparum and Toxoplasma gondii at low (i.e. IC50 congruent with150-2000 and 62 ng/ml, respectively) concentrations. Discovery and characterisation of an apicomplexan Fab I and discovery of triclosan as lead compound provide means to rationally design novel inhibitory compounds.
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Affiliation(s)
- R McLeod
- Department of Ophthalmology and Visual Sciences, The University of Chicago, Chicago, IL 60637, USA.
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86
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Abstract
An extrachromosomal genome of between 27 and 35 kb has been described in several apicomplexan parasites including Plasmodium falciparum and Toxoplasma gondii. Examination of sequence data proved the genomes to be a remnant plastid genome, from which all genes encoding photosynthetic functions had been lost. Localisation studies had shown that the genome was located within a multi-walled organelle, anterior to the nucleus. This organelle had been previously described in ultrastructural studies of several genera of apicomplexa, but no function had been attributed to it. This invited review describes the evolution of knowledge on the apicomplexan plastid, then discusses current research findings on the likely role of the plastid in the Apicomplexa. How the plastid may be used to effect better drug treatments for apicomplexan diseases, and its potential as a marker for investigating phylogenetic relationships among the Apicomplexa, are discussed.
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Affiliation(s)
- M T Gleeson
- Department of Cell and Molecular Biology, Faculty of Science, University of Technology, Westbourne Street, Gore Hill NSW 2065, Sydney, Australia.
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87
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Vial HJ. Isoprenoid biosynthesis and drug targeting in the Apicomplexa. PARASITOLOGY TODAY (PERSONAL ED.) 2000; 16:140-1. [PMID: 10725898 DOI: 10.1016/s0169-4758(00)01638-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- H J Vial
- Dynamique Moléculaire des Interactions membranaires, UMR 5539 CNRS, Université Montpellier II, Montpellier Cedex 5, France.
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88
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Nikolskaya T, Zagnitko O, Tevzadze G, Haselkorn R, Gornicki P. Herbicide sensitivity determinant of wheat plastid acetyl-CoA carboxylase is located in a 400-amino acid fragment of the carboxyltransferase domain. Proc Natl Acad Sci U S A 1999; 96:14647-51. [PMID: 10588759 PMCID: PMC24490 DOI: 10.1073/pnas.96.25.14647] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A series of chimeral genes, consisting of the yeast GAL10 promoter, yeast ACC1 leader, wheat acetyl-CoA carboxylase (ACCase; EC 6.4.1.2) cDNA, and yeast ACC1 3'-tail, was used to complement a yeast ACC1 mutation. These genes encode a full-length plastid enzyme, with and without the putative chloroplast transit peptide, as well as five chimeric cytosolic/plastid proteins. Four of the genes, all containing at least half of the wheat cytosolic ACCase coding region at the 5'-end, complement the yeast mutation. Aryloxyphenoxypropionate and cyclohexanedione herbicides, at concentrations below 10 microM, inhibit the growth of haploid yeast strains that express two of the chimeric ACCases. This inhibition resembles the inhibition of wheat plastid ACCase observed in vitro and in vivo. The differential response to herbicides localizes the sensitivity determinant to the third quarter of the multidomain plastid ACCase. Sequence comparisons of different multidomain and multisubunit ACCases suggest that this region includes part of the carboxyltransferase domain, and therefore that the carboxyltransferase activity of ACCase (second half-reaction) is the target of the inhibitors. The highly sensitive yeast gene-replacement strains described here provide a convenient system to study herbicide interaction with the enzyme and a powerful screening system for new inhibitors.
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Affiliation(s)
- T Nikolskaya
- Department of Molecular Genetics, University of Chicago, 920 East 58th Street, Chicago, IL 60637, USA
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