Affinage · Plasmodium

TPx1

PF3D7_1438900 · thioredoxin peroxidase 1

Annotated
2026-09-08
21 papers in source corpus 16 papers cited in narrative 16 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

Trx-Px1 (PF3D7_1438900) is a cytosolic 2-Cys peroxiredoxin that serves as a terminal peroxidase of the Plasmodium thioredoxin antioxidant system, catalyzing the reduction of hydrogen peroxide, organic hydroperoxides, and peroxynitrite (PMID:11231293, PMID:16307478). It operates by a ping-pong mechanism in which the peroxidatic Cys50 is oxidized and forms an intermolecular disulfide with Cys170′ of the partner subunit, a covalent dimer that is resolved by electron donors: mutation of C170 abolishes dimer formation and reduces catalytic efficiency ~50-fold, whereas C74 is dispensable (PMID:16307478). Reducing equivalents are supplied by P. falciparum thioredoxin and by the parasite-specific protein plasmoredoxin (PMID:11231293, PMID:16307478). The enzyme assembles into decameric, doughnut-shaped oligomers of five homodimers (PMID:12946843), and is expressed constitutively in the cytosol across the erythrocytic stages (PMID:15710548, PMID:21203490). Its activity is subject to redox-regulatory S-glutathionylation (PMID:21595565), and its transcription is controlled by histone acetylation and PfGCN5 recruitment at 5′ cis-regulatory elements (PMID:18692528). Genetic disruption establishes a protective role against oxidative and nitrosative stress in P. falciparum (PMID:12860402) and against fever-range heat stress, a function not shared by the other cytosolic peroxiredoxin (PMID:23201565). Across the life cycle in P. berghei, TPx-1 is dispensable for asexual blood-stage growth but required for efficient gametocyte production (PMID:16597467), sporozoite formation and genome integrity in mosquito oocysts (PMID:18417228), and merozoite production during liver schizogony (PMID:25284813). Beyond antioxidant catalysis, Trx-Px1 localizes to a nuclear peripheral subcompartment in ring-stage parasites, associates with the var antisense lncRNA interactome and PfSAMS, and modulates var gene activation and switching, implicating it as a redox-sensing nuclear factor linking cellular redox state to epigenetic control of virulence-gene transcription (PMID:35939693).

Mechanistic history

Synthesis pass · year-by-year structured walk · 15 steps
  1. 2001 High

    Establishing that PF3D7_1438900 is an enzymatically active 2-Cys peroxiredoxin defined its core biochemical identity as a thioredoxin-dependent peroxidase.

    Evidence In vitro kinetic assays with purified recombinant protein and P. falciparum thioredoxin, plus non-reducing SDS-PAGE showing disulfide-linked dimers

    PMID:11231293 PMID:11463468

    Open questions at the time
    • Physiological electron donors in vivo not yet defined beyond thioredoxin
    • Oligomeric state not resolved at this stage
  2. 2003 High

    Defining the catalytic kinetics and quaternary structure showed how the enzyme is organized, resolving that it functions as a decameric assembly rather than a simple dimer.

    Evidence Stopped-flow rapid kinetics giving ping-pong parameters, plus gel filtration, cross-linking, and electron microscopy showing doughnut-shaped decamers

    PMID:12946843

    Open questions at the time
    • Functional significance of decamerization for catalysis or regulation not established
    • No high-resolution atomic structure
  3. 2003 High

    Genetic knockout in P. falciparum answered whether the enzyme's antioxidant activity is physiologically protective, linking it to defense against oxidative and nitrosative stress.

    Evidence Gene targeting in P. falciparum with paraquat and sodium nitroprusside stress assays

    PMID:12860402

    Open questions at the time
    • Whether protection is direct catalysis or indirect not distinguished
    • No effect on normal growth quantified
  4. 2005 High

    Active-site mutagenesis and substrate profiling defined the catalytic cycle at residue resolution and identified plasmoredoxin as a second reducing substrate, extending the enzyme's redox network.

    Evidence Stopped-flow measurements of peroxynitrite reduction plus site-directed mutagenesis (C50/C170/C74) and non-reducing SDS-PAGE

    PMID:16307478

    Open questions at the time
    • Relative in vivo contributions of thioredoxin versus plasmoredoxin not quantified
    • Physiological relevance of peroxynitrite reduction in the parasite unmeasured
  5. 2005 Medium

    Expression profiling established the enzyme as a constitutively expressed cytosolic housekeeping antioxidant across the erythrocytic cycle.

    Evidence Quantitative RT-PCR, Western blotting, and confocal microscopy across ring, trophozoite, and schizont stages

    PMID:15710548

    Open questions at the time
    • Localization shown without direct functional consequence
    • Stage-specific quantitative levels not tied to activity
  6. 2008 Medium

    Chromatin and reporter analysis addressed how the gene is transcriptionally regulated, linking its expression to histone acetylation and PfGCN5 recruitment at defined 5′ elements.

    Evidence Reporter assays, ChIP, EMSA, and DNase I footprinting on the pftpx-1 5′ region

    PMID:18692528

    Open questions at the time
    • Specific cis-element residues not functionally validated
    • Trans-acting factors binding the elements not identified
  7. 2006 High

    Knockout in P. berghei tested requirement beyond the asexual stage, revealing a role in sexual-stage gametocyte development.

    Evidence Gene disruption in P. berghei with gametocyte counts and exflagellation assays

    PMID:16597467

    Open questions at the time
    • Mechanism linking peroxidase activity to gametocytogenesis unknown
    • Blood-stage growth unaffected, so context-dependence unexplained
  8. 2008 High

    Mosquito-stage knockout analysis extended the enzyme's role to sporozoite formation and revealed a link between its loss and genome integrity.

    Evidence P. berghei knockout with mosquito infection, sporozoite counts, DNA strand-break (comet) assay, and mouse infectivity

    PMID:18417228

    Open questions at the time
    • Source of DNA damage in KO oocysts not mechanistically defined
    • Liver invasion unaffected, limiting phenotype to sporozoite production
  9. 2010 Medium

    Systematic localization confirmed the cytosolic targeting of PF3D7_1438900 and distinguished it from an apicoplast-targeted sibling peroxiredoxin.

    Evidence Fluorescent-fusion confocal microscopy and fractionation across the plasmodial redox network

    PMID:21203490

    Open questions at the time
    • Nuclear localization not detected in this study
    • Fusion tagging may not capture minor subcompartment pools
  10. 2011 Medium

    Proteomic and biochemical identification of S-glutathionylation revealed a redox-regulatory post-translational modification on the enzyme.

    Evidence Affinity purification of glutathionylated proteins with MS and biochemical mixed-disulfide analysis

    PMID:21595565

    Open questions at the time
    • Functional effect of glutathionylation on activity not quantified
    • Modified residue not definitively mapped
  11. 2012 High

    Comparative knockout demonstrated a heat-stress protective role unique to PF3D7_1438900 among cytosolic peroxiredoxins, showing functional non-redundancy.

    Evidence Parallel knockout of PfTPx-1 and Pf1-Cys-Prx with fever-range heat stress assays

    PMID:23201565

    Open questions at the time
    • Molecular basis of heat protection versus oxidative protection not distinguished
    • Whether heat sensitivity reflects protein or substrate changes unknown
  12. 2013 Medium

    Analysis of ookinete-stage knockouts revealed compensatory upregulation of 1-Cys Prx and ROS-responsive transcription of the gene, illuminating its integration into stage-specific redox defense.

    Evidence RT-PCR, confocal immunofluorescence, and ROS challenge of cultured P. berghei ookinetes

    PMID:23382676

    Open questions at the time
    • Direct interaction with 1-Cys Prx not shown
    • Signaling pathway driving ROS-responsive transcription undefined
  13. 2014 Medium

    Liver-stage knockout analysis established a requirement for the enzyme in merozoite production during hepatic schizogony.

    Evidence P. berghei knockout with anti-CSP/anti-MSP-1 immunofluorescence in an in vitro liver infection system

    PMID:25284813

    Open questions at the time
    • Cause of reduced schizont size not mechanistically defined
    • Single-lab observation without complementation
  14. 2014 Medium

    In vitro assays with the P. knowlesi ortholog uncovered nucleic-acid binding and RNA chaperone activity, indicating a moonlighting function beyond peroxidase catalysis.

    Evidence Recombinant PkTPx-1 nucleic acid binding and melting (chaperone) assays plus immunofluorescence

    PMID:25092384

    Open questions at the time
    • Shown for the P. knowlesi ortholog, not P. falciparum PF3D7_1438900
    • In vivo relevance of nucleic-acid binding not demonstrated
  15. 2022 Medium

    Nuclear localization and var lncRNA association experiments recast PF3D7_1438900 as a redox-sensing nuclear regulator of virulence-gene transcription, connecting redox state to epigenetic control.

    Evidence RNA immunoprecipitation of the var antisense lncRNA interactome, confocal co-localization with PfSAMS, and overexpression/knockdown with var expression readouts in P. falciparum

    PMID:35939693

    Open questions at the time
    • Whether nuclear function requires peroxidase catalysis or redox state unresolved
    • Mechanism of recruitment to nuclear periphery unknown
    • Direct versus indirect effect on var switching not fully distinguished

Open questions

Synthesis pass · forward-looking unresolved questions
  • How Trx-Px1 physically bridges its cytosolic antioxidant catalysis and its nuclear role in var gene regulation, and whether one function depends on the redox chemistry of the other, remains unresolved.
  • No mechanism linking peroxidase catalytic cycle to nuclear transcriptional control
  • Structural basis of nucleic-acid/lncRNA binding by P. falciparum protein not defined
  • Whether the same molecular pool performs both roles unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
GLUTATHIONE (MIXED DISULFIDE/S-GLUTATHIONYLATION) [#10]P. FALCIPARUM THIOREDOXIN (PFTRX) [#0, #4]PFGCN5 HISTONE ACETYLTRANSFERASE (AT 5' REGULATORY REGION) [#8]PLASMOREDOXIN [#4]S-ADENOSYLMETHIONINE SYNTHETASE (PFSAMS) [#15]VAR ANTISENSE LNCRNA INTERACTOME [#15]
Complex memberships
Disulfide-linked homodimer via Cys50-Cys170' [#1, #4]Homodecamer (pentamer of homodimers) [#2]

Evidence

Reading pass · 16 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2001 Trx-Px1 (PfTPx1) is a 2-Cys peroxiredoxin that catalyzes thioredoxin-dependent reduction of H2O2, t-butylhydroperoxide, and cumene hydroperoxide; it is reduced by P. falciparum thioredoxin (PfTrx) with kcat values of 67, 56, and 41 min−1 for the three substrates respectively; in oxidizing conditions it converts to a faster-migrating species with altered kinetic properties, suggesting in vivo regulation. In vitro enzymatic assay (glutamine synthetase protector assay, kinetic measurements with purified recombinant protein), SDS-PAGE under oxidizing conditions European journal of biochemistry High 11231293
2001 Trx-Px1 (PfPrx-1) forms disulfide-linked dimers under non-reducing conditions and dissociates into monomers in the presence of DTT; it acts as a terminal peroxidase of the parasite thioredoxin system, accepting electrons from E. coli Trx/thioredoxin reductase to reduce H2O2. Recombinant protein expression in E. coli, non-reducing SDS-PAGE, enzymatic assay with E. coli Trx system Molecular and biochemical parasitology High 11463468
2003 Trx-Px1 (PfTrx-Px1) exhibits ping-pong kinetics with Km values of 0.78 µM for H2O2 and 18.94 µM for thioredoxin; it forms decamers (pentamers of homodimers) with a doughnut-like shape by gel filtration, cross-linking, and electron microscopy, with no detectable dimeric forms after gel filtration. Stopped-flow rapid kinetics, gel filtration, chemical cross-linking, electron microscopy Molecular and biochemical parasitology High 12946843
2003 Genetic disruption of Trx-Px1 (PfTPx-1) in P. falciparum renders parasites hypersensitive to paraquat (superoxide donor) and sodium nitroprusside (nitric oxide donor), establishing that Trx-Px1 protects the parasite from oxidative and nitrosative stress. Gene targeting (knockout) in P. falciparum, chemical stress assays with paraquat and sodium nitroprusside FEBS letters High 12860402
2005 Trx-Px1 (TPx1) reduces peroxynitrite (ONOO−) with a rate constant of ~1×10^6 M−1 s−1 (pH 7.4, 37°C); plasmoredoxin (a parasite-specific 22-kDa protein) was identified as a novel reducing substrate of TPx1 in addition to thioredoxin; the catalytic cycle proceeds via oxidation of peroxidatic Cys50 followed by intermolecular disulfide bond formation between Cys50 and Cys170′ of the partner subunit, which is then resolved by thioredoxin or plasmoredoxin; mutation C170A abolishes covalent dimer formation and reduces kcat/Km ~50-fold, while C74A mutation does not affect dimerization or activity. Stopped-flow measurements, site-directed mutagenesis (C74A, C170A), in vitro enzymatic assay, non-reducing SDS-PAGE Biological chemistry High 16307478
2005 Trx-Px1 (PfTPx-1) is expressed constitutively in the parasite cytoplasm throughout the erythrocytic stage (ring, trophozoite, schizont), consistent with a housekeeping role in controlling intracellular ROS. Real-time quantitative RT-PCR, Western blotting, confocal laser scanning microscopy Parasitology international Medium 15710548
2006 Disruption of TPx-1 in P. berghei does not impair asexual blood-stage growth but reduces gametocyte production by up to 60% and delays peak gametocytemia, establishing a role for TPx-1 in gametocyte development; male/female ratio and male exflagellation are unaffected. Gene disruption (knockout) in P. berghei, gametocyte counts, exflagellation assay Molecular and biochemical parasitology High 16597467
2008 Disruption of TPx-1 in P. berghei does not affect midgut oocyst numbers but reduces sporozoite formation in oocysts to 10–20% and salivary gland sporozoite accumulation to 3–10% of wild-type; TPx-1-KO sporozoites show increased DNA strand breaks in oocysts, and have reduced infectivity in mice, though liver invasion and EEF initiation are unaffected. Gene disruption (knockout) in P. berghei, mosquito infection experiment, sporozoite counts, comet/DNA strand-break assay, mouse infection Molecular and biochemical parasitology High 18417228
2008 Transcriptional activity of the pftpx-1 gene correlates with increased histone acetylation in its 5′ region, and reporter assays reveal putative enhancer elements in the 5′ region; chromatin immunoprecipitation showed that PfGCN5 histone acetyltransferase recruitment to these regulatory regions correlates with transcriptional activity. Reporter assay, chromatin immunoprecipitation (ChIP), electrophoretic mobility shift assay (EMSA), DNase I footprinting Molecular and biochemical parasitology Medium 18692528
2010 Trx-Px1 localizes to the parasite cytosol in P. falciparum erythrocytic stages; a second plasmodial peroxiredoxin (TPx2) is targeted to the apicoplast, and differential targeting of glutathione reductase and thioredoxin reductase is achieved by alternative translation initiation. Systematic subcellular localization study using fluorescent protein fusions and confocal microscopy, fractionation PLoS pathogens Medium 21203490
2011 Trx-Px1 (thioredoxin peroxidase 1) is a target of protein S-glutathionylation in P. falciparum, identified by affinity purification of biotinylated glutathionylated proteins followed by proteomics; its ability to form mixed disulfides with glutathione was confirmed by biochemical analysis. Affinity purification (biotin-maleimide tagging after enzymatic deglutathionylation), mass spectrometry proteomics, biochemical mixed-disulfide analysis Antioxidants & redox signaling Medium 21595565
2012 Disruption of PfTPx-1 in P. falciparum renders parasites hypersensitive to heat stress (fever-range temperatures), demonstrating a hyperthermal protective function distinct from other cytoplasmic peroxiredoxins; Pf1-Cys-Prx knockout lines did not show heat stress hypersensitivity, indicating the two cytosolic peroxiredoxins have independent functions. Gene disruption (knockout) of PfTPx-1 and Pf1-Cys-Prx in P. falciparum, heat stress assay, comparison of phenotypes Parasitology international High 23201565
2013 In P. berghei TPx-1 knockout ookinetes, 1-Cys Prx expression occurs significantly earlier and is detectable under culture conditions (where it is normally absent), indicating that 1-Cys Prx partially compensates for loss of TPx-1 in the ookinete stage; tpx-1 transcript is upregulated in a dose-dependent manner when cultured ookinetes are challenged with exogenous ROS. Transcriptional profiling (RT-PCR), confocal immunofluorescence imaging, TPx-1 KO parasite analysis, ROS challenge assay PLoS pathogens Medium 23382676
2014 Disruption of TPx-1 in P. berghei results in significantly smaller liver schizonts and fewer merozoites produced per mature schizont compared to wild-type, establishing a role for TPx-1 in merozoite formation during liver schizont development. Gene disruption (knockout) in P. berghei, indirect immunofluorescence microscopy with anti-CSP and anti-MSP-1 antibodies, in vitro liver infection system Parasitology international Medium 25284813
2014 P. knowlesi TPx-1 (PkTPx-1) binds double-stranded DNA and RNA and has RNA chaperone activity demonstrated in a nucleic acid melting assay, indicating a function beyond antioxidant activity; it is expressed in the cytoplasm of the parasite. Recombinant protein expression, mixed-function oxidation assay, nucleic acid binding assay, RNA chaperone (nucleic acid melting) assay, indirect immunofluorescence microscopy Parasitology research Medium 25092384
2022 Trx-Px1 (PfTPx-1) localizes to a nuclear subcompartment associated with active transcription on the nuclear periphery in ring-stage P. falciparum; it associates with the var antisense lncRNA interactome; it co-localizes with S-adenosylmethionine synthetase (PfSAMS) in the nucleus; overexpression of Trx-Px1 activates var2csa expression (similar to PfSAMS overexpression); and Trx-Px1 knockdown alters the var gene switch rate and affects activation of additional gene subsets, indicating a role as a redox-controlled nuclear factor in var gene transcription regulation. RNA immunoprecipitation (var lncRNA interactome), confocal co-localization microscopy, overexpression and knockdown experiments with var gene expression assays (RT-PCR/reporter), nuclear fractionation Proceedings of the National Academy of Sciences of the United States of America Medium 35939693

Source papers

Stage 0 corpus · 21 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2010 Compartmentation of redox metabolism in malaria parasites. PLoS pathogens 122 21203490
2011 Protein S-glutathionylation in malaria parasites. Antioxidants & redox signaling 87 21595565
2001 Thioredoxin peroxidases of the malarial parasite Plasmodium falciparum. European journal of biochemistry 63 11231293
2005 Expression of mRNAs and proteins for peroxiredoxins in Plasmodium falciparum erythrocytic stage. Parasitology international 47 15710548
2003 2-Cys peroxiredoxin PfTrx-Px1 is involved in the antioxidant defence of Plasmodium falciparum. Molecular and biochemical parasitology 45 12946843
2001 Isolation and functional analysis of two thioredoxin peroxidases (peroxiredoxins) from Plasmodium falciparum. Molecular and biochemical parasitology 45 11295184
2001 Molecular characterization of a 2-Cys peroxiredoxin from the human malaria parasite Plasmodium falciparum. Molecular and biochemical parasitology 44 11463468
2003 Disruption of the Plasmodium falciparum 2-Cys peroxiredoxin gene renders parasites hypersensitive to reactive oxygen and nitrogen species. FEBS letters 42 12860402
2005 Plasmodium falciparum 2-Cys peroxiredoxin reacts with plasmoredoxin and peroxynitrite. Biological chemistry 30 16307478
2006 2-Cys Peroxiredoxin TPx-1 is involved in gametocyte development in Plasmodium berghei. Molecular and biochemical parasitology 27 16597467
2013 Expression of cytosolic peroxiredoxins in Plasmodium berghei ookinetes is regulated by environmental factors in the mosquito bloodmeal. PLoS pathogens 20 23382676
2012 Cloning and characterization of Plasmodium vivax thioredoxin peroxidase-1. Parasitology research 20 22392134
2008 Disruption of the Plasmodium berghei 2-Cys peroxiredoxin TPx-1 gene hinders the sporozoite development in the vector mosquito. Molecular and biochemical parasitology 20 18417228
2012 2-Cys peroxiredoxin of Plasmodium falciparum is involved in resistance to heat stress of the parasite. Parasitology international 17 23201565
2022 A nuclear redox sensor modulates gene activation and var switching in Plasmodium falciparum. Proceedings of the National Academy of Sciences of the United States of America 15 35939693
2014 Plasmodium knowlesi thioredoxin peroxidase 1 binds to nucleic acids and has RNA chaperone activity. Parasitology research 12 25092384
2008 5' sequence- and chromatin modification-dependent gene expression in Plasmodium falciparum erythrocytic stage. Molecular and biochemical parasitology 11 18692528
2015 Development of monoclonal antibodies against Plasmodium falciparum thioredoxin peroxidase 1 and its possible application for malaria diagnosis. Experimental parasitology 9 25913091
2014 Effect of thioredoxin peroxidase-1 gene disruption on the liver stages of the rodent malaria parasite Plasmodium berghei. Parasitology international 9 25284813
2012 Crystal structures from the Plasmodium peroxiredoxins: new insights into oligomerization and product binding. BMC structural biology 8 22429898
2012 Expression profiles of peroxiredoxins in liver stage of the rodent malaria parasite Plasmodium berghei. Parasitology international 4 23237790