exoneme

GO:0044311 · Membrane organelle · Membrane bounded organelle · Proposed

A dense granule-like organelle of the apical complex of merozoites, released into the parasitophorous vacuole, mediating protease-dependent rupture and parasite exit from the infected erythrocyte. [GO:0044311]

Part of: apical complex (GO:0020007)

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
PfSUB1 exoneme protease	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	sub1		UNKNOWN	Secretory subtilisin-like serine protease stored in exonemes and released into the parasitophorous vacuole shortly before egress to process SERA and merozoite-surface protein substrates. `DOI:10.1016/j.cell.2007.10.049` Yeoh et al. 2007 identified PfSUB1 in dense granule-like exonemes and connected its regulated release to SERA processing, egress, and merozoite invasion competence. `DOI:10.1111/j.1462-5822.2008.01176.x` Blackman 2008 reviews PfSUB1 discharge from exonemes into the PV space just before P. falciparum blood-stage egress.
plasmepsin X exoneme protease	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	pmx		UNKNOWN	Exoneme-localized aspartic protease that supports the final maturation step of the PfSUB1 egress protease. `DOI:10.1126/science.aan1478` Nasamu et al. 2017 localized Plasmepsin X to exonemes and linked PMX knockdown to impaired SUB1 maturation and egress.

Taxonomic distribution

NCBITaxon:5833 Plasmodium falciparum — COMMON: Exonemes are directly evidenced in Plasmodium falciparum segmented schizonts and blood-stage merozoites; no broader apicomplexan distribution is asserted in this first record. [DOI:10.1016/j.cell.2007.10.049]

Canonical examples

NCBITaxon:5833 Plasmodium falciparum — Human malaria parasite in which PfSUB1 discharge from exonemes into the parasitophorous vacuole was tied to SERA processing and erythrocyte egress. [DOI:10.1016/j.cell.2007.10.049]

Functions

regulated PfSUB1 discharge — Exonemes release PfSUB1 into the parasitophorous vacuole shortly before P. falciparum erythrocyte egress.
- DOI:10.1111/j.1462-5822.2008.01176.x Blackman 2008 reviews the regulated release of PfSUB1 from exonemes into the PV space just before egress.
- DOI:10.1038/ncomms4726 Withers-Martinez et al. 2014 describe SUB1 discharge from exonemes into the PV lumen minutes before egress.
erythrocyte egress protease delivery — Exoneme discharge delivers mature PfSUB1 to process SERA and MSP substrates that support rupture of the parasitophorous vacuole and erythrocyte membranes.
- DOI:10.1016/j.cell.2007.10.049 Yeoh et al. 2007 connected PfSUB1 exoneme discharge to SERA maturation, host-cell egress, and the invasive capacity of released merozoites.
- DOI:10.1126/science.aan1478 Nasamu et al. 2017 placed PMX upstream of SUB1 maturation and SERA5/MSP1 processing in the P. falciparum egress cascade.

Mechanism graphs

Plasmepsin X and PfSUB1 connect exonemes to erythrocyte egress (FUNCTION)

PMX localizes to exonemes and supports final maturation of PfSUB1; exonemes discharge PfSUB1 into the PV, where the protease processes SERA/MSP substrates required for P. falciparum egress and post-egress invasion.

Subject	Predicate	Object	Evidence
plasmepsin X exoneme protease	localizes to	exoneme	`DOI:10.1126/science.aan1478` Nasamu et al. 2017 localized PMX to exonemes by immuno-electron microscopy.
plasmepsin X exoneme protease	supports maturation of	PfSUB1 exoneme protease	`DOI:10.1126/science.aan1478` Nasamu et al. 2017 found that PMX knockdown blocked the second SUB1 maturation step.
PfSUB1 exoneme protease	resides in	exoneme	`DOI:10.1016/j.cell.2007.10.049` Yeoh et al. 2007 identified PfSUB1 in previously unrecognized organelles termed exonemes.
exoneme	discharges	PfSUB1 exoneme protease	`DOI:10.1111/j.1462-5822.2008.01176.x` Blackman 2008 reviews PfSUB1 release from exonemes into the PV space just prior to egress.
PfSUB1 exoneme protease	is discharged into	parasitophorous vacuole	`DOI:10.1038/ncomms4726` Withers-Martinez et al. 2014 describe SUB1 release into the PV lumen minutes before egress.
PfSUB1 exoneme protease	processes	SERA and MSP substrates	`DOI:10.1126/science.aan1478` Nasamu et al. 2017 connected PMX-dependent SUB1 maturation to SERA5 and MSP1 processing.
SERA and MSP substrates	support	erythrocyte egress	`DOI:10.1038/ncomms4726` Withers-Martinez et al. 2014 review SUB1 cleavage of egress and invasion substrates.
PfSUB1 exoneme protease	supports	merozoite invasion capacity	`DOI:10.1016/j.cell.2007.10.049` Yeoh et al. 2007 found that PfSUB1 blockade inhibited egress and ablated the invasive capacity of released merozoites.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral groundings for Plasmodium SUB1 and plasmepsin X exoneme protein families. The first exoneme record keeps P. falciparum SUB1 and PMX label-only because no exact cross-source family CURIE was curated for either exoneme protease.

Evidence

DOI:10.1016/j.cell.2007.10.049 Yeoh et al. 2007, Subcellular discharge of a serine protease mediates release of invasive malaria parasites from host erythrocytes, Cell.
DOI:10.1111/j.1462-5822.2008.01176.x Blackman 2008, Malarial proteases and host cell egress: an 'emerging' cascade, Cellular Microbiology.
DOI:10.1038/ncomms4726 Withers-Martinez et al. 2014, The malaria parasite egress protease SUB1 is a calcium-dependent redox switch subtilisin, Nature Communications.
DOI:10.1126/science.aan1478 Nasamu et al. 2017, Plasmepsins IX and X are essential and druggable mediators of malaria parasite egress and invasion, Science.

Curation history

2026-09-10T06:21:28Z claude · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-10T06:23:06Z claude · EXPANDED_RECORD — Added GO apical-complex parthood, PfSUB1 and plasmepsin X components, rare eukaryotic and apicomplexan taxonomic scope, Plasmodium falciparum as a canonical example, SUB1 discharge and egress-protease-delivery functions, a PMX/SUB1 egress graph, and an exoneme-protease grounding TODO.
2026-09-10T06:34:03Z claude · TIGHTENED_PMX_SCOPE — Renamed the plasmepsin X exoneme component and graph node to avoid overstating direct maturase activity, and narrowed the PMX-to-SUB1 edge predicate to supported final SUB1 maturation.
2026-09-10T06:34:25Z claude · FIXED_DISCUSSION_ANCHOR — Updated the plasmepsin X grounding discussion anchor after the component id was narrowed to plasmepsin_x_exoneme_protease.
2026-09-10T06:41:09Z claude · NARROWED_TAXONOMIC_SCOPE — Replaced Eukaryota and Apicomplexa distribution rows with a directly evidenced Plasmodium falciparum row to avoid broader taxonomic claims than the exoneme sources support.

Source: data/structures/membrane_organelle/exoneme.yaml