Affinage · Plasmodium

PF3D7_1442000

ADP-ribosylation factor, putative

Audit flag: identity unverified
Annotated
2026-09-08
11 papers in source corpus 5 papers cited in narrative 5 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PF3D7_1442000 is a functional class I ADP-ribosylation factor (ARF1) of Plasmodium falciparum that acts as a GDP/GTP-binding small GTPase governing early secretory trafficking in blood-stage parasites (PMID:8954160, PMID:33604307). Recombinant PfARF1 purifies with stoichiometrically bound GDP, exchanges GDP for GTP with first-order kinetics, and stimulates cholera-toxin-catalyzed ADP-ribosyltransferase activity in a phospholipid-dependent reaction, confirming its identity as a functional ARF; no intrinsic GTPase activity was detected (PMID:8954160). Its GDP-bound crystal structure at 2.5 Å shows the fold is conserved with mammalian class I ARF1s (PMID:21045287). Consistent with its N-myristoylation, PfARF1 localizes to a Golgi/ER-proximal compartment, occupying an ER subdomain distinct from PfRab1b and co-localizing with (and co-immunoprecipitating) PfRab5b (PMID:25909331, PMID:33604307). At this ER exit step it sorts the non-PEXEL cargo PfAK2 into the parasitophorous-vacuole pathway and cooperates with PfRab1b in export of the PEXEL protein Rifin, since an inactive GTPase mutant blocks PfAK2 trafficking and reduces Rifin export (PMID:33604307). In vitro, PfARF1 activates the parasite's unique bifunctional PIP5K, linking it to PtdIns(4,5)P₂ synthesis (PMID:19171150). Beyond these secretory and lipid-signaling roles, no further mechanistic detail has been characterized in the available corpus.

Mechanistic history

Synthesis pass · year-by-year structured walk · 5 steps
  1. 1996 High

    Establishing whether the P. falciparum ARF1 gene product is a bona fide functional GTPase was the first step in assigning it to the class I ARF family.

    Evidence Recombinant expression in E. coli with GTP-binding kinetics and cholera-toxin ADP-ribosyltransferase stimulation assays

    PMID:8954160

    Open questions at the time
    • No intrinsic GTPase activity detected, so the GAP/GEF regulators are unidentified
    • No cellular localization or trafficking role addressed in vitro
  2. 2009 Medium

    Testing whether PfARF1 feeds into parasite lipid signaling revealed it as an upstream activator of the unique PfPIP5K, connecting the GTPase to PtdIns(4,5)P2 synthesis.

    Evidence In vitro kinase activation assay with recombinant PfARF1 and PfPIP5K

    PMID:19171150

    Open questions at the time
    • Single lab, single in vitro method; not confirmed in cellular context
    • Physiological consequence of PtdIns(4,5)P2 output not defined
  3. 2010 High

    Solving the GDP-bound structure provided an atomic framework confirming conservation of the class I ARF fold in the parasite.

    Evidence X-ray crystallography of PfARF1 at 2.5 Å

    PMID:21045287

    Open questions at the time
    • Only the GDP-bound (inactive) state captured; no GTP-bound/active conformation
    • No structure of complexes with effectors or regulators
  4. 2015 Medium

    Localizing PfARF1 to a Golgi compartment and dissecting membrane-targeting signals clarified which motifs govern its subcellular positioning and distinguished it from cargo it traffics.

    Evidence GFP-fusion live microscopy, Golgi-marker co-localization, and PfARF1/PfAK2 chimeric construct analysis

    PMID:25909331

    Open questions at the time
    • Single lab imaging study
    • N-myristoylation shown insufficient for PVM targeting, but the sufficient signal set unresolved
  5. 2021 Medium

    Placing PfARF1 at an ER exit step and defining its trafficking partners established its role in sorting non-PEXEL cargo and cooperating in PEXEL-protein export.

    Evidence Reciprocal Co-IP/MS with PfRab5b, super-resolution microscopy versus PfRab1b, and inactive-GTPase-mutant trafficking phenotypes for PfAK2 and Rifin

    PMID:33604307

    Open questions at the time
    • Single lab; dominant-mutant approach rather than direct loss-of-function
    • Mechanistic basis of cargo selectivity between PV and export pathways unresolved
    • Functional significance of the PfRab5b interaction not dissected

Open questions

Synthesis pass · forward-looking unresolved questions
  • How PfARF1 nucleotide cycling is regulated in vivo, and how its GTPase, lipid-kinase-activating, and cargo-sorting activities are integrated, remains unresolved.
  • No GEF/GAP identified for PfARF1
  • No GTP-bound structure or effector-bound structure
  • Direct essentiality and loss-of-function phenotype not established in the corpus

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
PFPIP5K (ACTIVATED IN VITRO) [#1]PFRAB1B (DISTINCT ER SUBDOMAIN; COOPERATES IN RIFIN EXPORT) [#4]PFRAB5B (CO-IP, CO-LOCALIZATION) [#4]

Evidence

Reading pass · 5 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1996 Recombinant P. falciparum ARF1 (PF3D7_1442000) was purified with stoichiometric amounts of bound GDP; it bound GTP with first-order kinetics (apparent rate constant k' = 0.0145 min⁻¹) and stimulated cholera-toxin-catalyzed ADP-ribosyltransferase activity in a reaction dependent on dimyristoylglycerophosphocholine and cholate, confirming it is a functional class I ARF GTPase. No intrinsic GTPase activity was detected. Recombinant protein expression in E. coli, GTP-binding assay, cholera-toxin ADP-ribosyltransferase stimulation assay European journal of biochemistry High 8954160
2009 Recombinant P. falciparum ARF1 activates the unique P. falciparum PIP5K (a bifunctional phosphatidylinositol 4-phosphate 5-kinase) in vitro, whereas phosphatidic acid does not, placing PfARF1 upstream of PtdIns(4,5)P₂ synthesis in the parasite. In vitro kinase activation assay with recombinant proteins International journal for parasitology Medium 19171150
2010 The crystal structure of P. falciparum ARF1 (PF3D7_1442000) was determined in the GDP-bound conformation at 2.5 Å resolution, revealing structural similarity to mammalian class I ARF1s. X-ray crystallography Acta crystallographica. Section F, Structural biology and crystallization communications High 21045287
2015 PfARF1 localizes to a Golgi compartment in P. falciparum blood-stage parasites, consistent with its N-myristoylation. When a chimeric protein carrying the PfARF1 N-terminus plus the additional palmitoylation and lysine-cluster motifs from PfAK2 was expressed, it was retargeted to the parasite plasma membrane but was not translocated into the parasitophorous vacuole, demonstrating that N-myristoylation alone is insufficient for PVM targeting. GFP-fusion live fluorescence microscopy, chimeric protein analysis, co-localization with Golgi marker PloS one Medium 25909331
2021 PfARF1 was co-immunoprecipitated with PfRab5b and co-localizes with PfRab5b adjacent to the ER in early erythrocytic stage parasites. Super-resolution microscopy showed PfARF1 localizes to a distinct ER subdomain from PfRab1b. Expression of an inactive PfARF1 mutant specifically inhibited trafficking of the non-PEXEL protein PfAK2 to the parasitophorous vacuole membrane and also decreased export of the PEXEL-positive protein Rifin, placing PfARF1 at an ER exit step that sorts PfAK2 into the PV pathway and cooperates with PfRab1b in Rifin export. Co-immunoprecipitation, mass spectrometry, super-resolution immunofluorescence microscopy, active/inactive GTPase mutant expression Frontiers in cellular and infection microbiology Medium 33604307

Source papers

Stage 0 corpus · 11 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1996 Isolation, expression and characterization of the gene for an ADP-ribosylation factor from the human malaria parasite, Plasmodium falciparum. European journal of biochemistry 40 8954160
2009 A unique phosphatidylinositol 4-phosphate 5-kinase is activated by ADP-ribosylation factor in Plasmodium falciparum. International journal for parasitology 36 19171150
2015 Alternative Protein Secretion in the Malaria Parasite Plasmodium falciparum. PloS one 23 25909331
2001 A point mutation in an unusual Sec7 domain is linked to brefeldin A resistance in a Plasmodium falciparum line generated by drug selection. Molecular microbiology 21 11555294
1997 Cloning and characterization of Plasmodium falciparum ADP-ribosylation factor and factor-like genes. Molecular and biochemical parasitology 10 9084044
1997 Identification and characterization of an ADP-ribosylation factor in Plasmodium falciparum. Molecular and biochemical parasitology 10 9247933
2010 Structure of Plasmodium falciparum ADP-ribosylation factor 1. Acta crystallographica. Section F, Structural biology and crystallization communications 8 21045287
2004 Double cross-over gene replacement within the sec 7 domain of a GDP-GTP exchange factor from Plasmodium falciparum allows the generation of a transgenic brefeldin A-resistant parasite line. Molecular and biochemical parasitology 8 15500915
2021 Rab5b-Associated Arf1 GTPase Regulates Export of N-Myristoylated Adenylate Kinase 2 From the Endoplasmic Reticulum in Plasmodium falciparum. Frontiers in cellular and infection microbiology 7 33604307
2011 Structure of the catalytic domain of Plasmodium falciparum ARF GTPase-activating protein (ARFGAP). Acta crystallographica. Section F, Structural biology and crystallization communications 2 22102228
2024 Toxoplasma and Plasmodium associate with host Arfs during infection. mSphere 1 38349168