Characterization of a phosphoinositide-binding protein containing a PHOX homology domain in the malaria parasite Plasmodium falciparum
Bibliographic record
Abstract
Phosphoinositides (PIPs), are key regulators of membrane identity and vesicular trafficking. By dynamically shaping the lipid composition of intracellular membranes, PIPs help ensure the specificity of cargo delivery. In apicomplexan parasites such as Plasmodium falciparum, the biogenesis of the specialized secretory organelles involved in erythrocyte invasion (named rhoptries, micronemes, and dense granules), remains poorly understood, particularly regarding how proteins are sorted and specifically targeted to their respective destinations. Our hypothesis is that PIPs might play a role in this process. We here present our characterization of the P. falciparum protein Pf3D7_0704400, a putative PIP-binding protein containing a PX domain. We named this protein PfPX2, following the previously characterized PX domain-containing protein PfPX1. In silico structural analysis revealed that the PfPX2 PX domain contains both canonical and non-canonical PIP-binding motifs and a positively charged binding pocket. Lipid binding assays showed that the PfPX2 PX domain can bind all species of PIPs with a preference for PI3P, PI5P and PI(3,5)P2. Immunofluorescence assays demonstrated that PfPX2 localized to the Golgi apparatus and the micronemes in developing schizonts. Moreover, proximity labelling enabled the identification of protein such as PfSortilin, the clathrin heavy chain and PfDyn1 as potential interactors of PfPX2. Globally, these data suggest that PfPX2 is a PIP-binding protein potentially implicated in vesicular trafficking between the Golgi apparatus and the micronemes. Our bioinformatics analyses identified PX2 orthologues across apicomplexans and indeed other alveolates, raising the possibility that this protein plays a role in a broad range of medically, agriculturally, and environmentally relevant organisms.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".