PF3D7_1459100

PF3D7_1459100 encodes GTP cyclohydrolase I (GCH1), an enzyme that catalyzes the conversion of GTP to D-erythro-dihydroneopterin triphosphate with release of carbon-8 of GTP, an activity first purified and kinetically characterized from P. falciparum extracts (Km for GTP ~54.6 µM, Mg2+-independent, competitively inhibited by ATP) (PMID:3908934). Recombinant PfGCH1 is enzymatically active, adopts a Tunnelling-fold (T-fold) architecture in which the conserved core domain alone is sufficient for catalysis while peripheral domains are dispensable, is inhibited by the GTP analogue 8-oxo-GTP, and rescues a ΔfolE E. coli mutant, confirming its identity and defining catalytic residues (PMID:24745605). Proper folding of PfGCH1 into a soluble, functional form is assisted by the parasite chaperone PfHsp70 (PMID:21262365). Tandem amplification of the ~5 kb GCH1 locus arises in precise 2-unit steps at conserved AT-rich amplicon boundaries and is positively associated with amplification at the separately located DHODH locus in parasites selected for antimetabolite resistance, linking folate and pyrimidine biosynthesis at the genomic level (PMID:40676505). Beyond these findings, the in vivo cellular regulation and the identity of a regulatory partner protein have not been experimentally characterized in the available corpus.

1. 1985 High

   Establishing that P. falciparum possesses a GTP cyclohydrolase I activity answered whether the parasite carries the first, rate-limiting step of de novo folate biosynthesis as a discrete enzyme.

   Evidence ~200-fold enzyme purification with kinetic assay, product identification, and inhibitor characterization from Plasmodium extracts

   PMID:3908934

   Open questions at the time

   • Purified from parasite extract, so the gene identity of the activity was not molecularly assigned at this stage
   • Native subunit composition underlying the ~300,000 MW not resolved
   • No structural information on the catalytic site
2. 2011 Medium

   Co-expression with PfHsp70 addressed how PfGCH1 is folded into a functional state, showing the chaperone assists production of soluble active enzyme.

   Evidence Heterologous bacterial co-expression with nickel affinity purification and HPLC-fluorescence activity assay

   PMID:21262365

   Open questions at the time

   • A direct PfHsp70–PfGCH1 physical interaction was inferred from yield, not demonstrated by binding assay
   • Whether PfHsp70 chaperones GCH1 in the parasite in vivo is untested
   • Stoichiometry and folding intermediates undefined
3. 2014 High

   Recombinant expression, domain truncation, and ΔfolE complementation molecularly confirmed the gene product as a functional GCH1 and identified which domains and residues are required for catalysis.

   Evidence Bacterial recombinant expression, HPLC-fluorescence assay, domain truncation mutagenesis, ΔfolE genetic complementation, and homology modelling to a T-fold

   PMID:24745605

   Open questions at the time

   • T-fold assignment rests on homology modelling, not an experimental structure
   • Physiological relevance of 8-oxo-GTP inhibition in the parasite not addressed
   • Role of the dispensable peripheral domains not defined
4. 2021 Low

   Normal mode analysis probed how the T-fold tunnel opens for catalysis, predicting a shear/expansion gating motion and allosteric hotspots including in complex with a regulatory partner.

   Evidence Anisotropic network model normal mode analysis on a structural model

   PMID:34450011

   Open questions at the time

   • Purely computational with no experimental validation of the gating mechanism or hotspots
   • The identity of the 'regulatory partner protein' is not established for PF3D7_1459100 in this corpus
   • Predicted allosteric residues untested by mutagenesis
5. 2025 Medium

   Long-read sequencing of drug-selected lines defined the architecture of GCH1 locus amplification and linked it to pyrimidine-pathway resistance, addressing how copy-number variation at this gene arises and co-varies with DHODH amplification.

   Evidence Oxford Nanopore long-read sequencing with single-read visualization and copy-number quantification of a ~5 kb GCH1 amplicon

   PMID:40676505

   Open questions at the time

   • The functional/metabolic mechanism connecting GCH1 and DHODH amplification is correlative, not demonstrated
   • Whether increased GCH1 copy number raises enzyme activity or flux was not measured here
   • Mechanism selecting for 2-unit amplification steps not resolved

• How PfGCH1 catalysis and abundance are regulated in the intact parasite, and the identity of any in vivo regulatory partner, remain open.
• No experimental (non-homology) structure of PfGCH1
• No validated physical interactor or regulatory subunit identified for PF3D7_1459100
• Contribution of the gene to folate flux and drug resistance not tested by direct genetic manipulation