rhoptry neck

GO:1990225 · Membrane organelle · Other · Proposed

Narrow, electron-dense part of the rhoptry that extends through the conoid at the apical tip of an apicomplexan parasite. [GO:1990225]

Part of: rhoptry (GO:0020008)

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
rhoptry neck proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Rhoptry neck-localized secretory proteins that are released during host-cell invasion and contribute to the moving-junction interface. `PMID:16002398` Bradley et al. 2005 identified multiple RON proteins in the Toxoplasma gondii rhoptry proteome. `DOI:10.1371/journal.ppat.0010017` Alexander et al. 2005 showed that RON4 is a Toxoplasma rhoptry-neck protein that relocates to the moving junction during invasion.

Taxonomic distribution

NCBITaxon:5794 Apicomplexa — COMMON: Rhoptry necks are the narrow apical regions of apicomplexan rhoptries; their number and morphology vary among lineages and invasive life-cycle stages. [DOI:10.1128/mmbr.00197-22]

Canonical examples

NCBITaxon:5811 Toxoplasma gondii — Apicomplexan model in which RON proteins were identified in the rhoptry proteome and shown to relocate toward the moving junction during invasion. [PMID:16002398]

Functions

rhoptry neck secretion — The rhoptry neck forms the narrow electron-dense apical domain used as rhoptry contents are secreted during host-cell invasion.
- GO:1990225 GO:1990225 defines the rhoptry neck as the narrow part of the rhoptry that extends through the apical conoid.
- DOI:10.1038/nrmicro1800 Boothroyd and Dubremetz 2008 review neck and bulb compartmentation of Toxoplasma rhoptries during invasion.
moving junction assembly — Rhoptry neck proteins are secreted from the rhoptry neck and help form the moving junction that coordinates apicomplexan host-cell invasion.
- DOI:10.1371/journal.ppat.0010017 Alexander et al. 2005 showed that RON4 leaves the rhoptry neck and contributes to the moving-junction complex in Toxoplasma tachyzoites.

Mechanism graphs

Rhoptry neck dispatches RON proteins for invasion (FUNCTION)

The rhoptry neck is the narrow apical rhoptry domain through which rhoptry-neck proteins are secreted. In Toxoplasma, secreted RON proteins relocalize to the moving junction used for host-cell invasion.

Subject	Predicate	Object	Evidence
rhoptry neck	is part of	rhoptry	`GO:1990225` GO:1990225 defines the rhoptry neck as the narrow electron-dense part of the rhoptry. `DOI:10.1038/nrmicro1800` Boothroyd and Dubremetz 2008 review rhoptry neck and bulb compartmentation.
rhoptry neck proteins	reside in	rhoptry neck	`PMID:16002398` Bradley et al. 2005 identified rhoptry neck proteins in purified Toxoplasma rhoptries.
rhoptry neck proteins	assemble at	moving junction	`DOI:10.1371/journal.ppat.0010017` Alexander et al. 2005 identified RON4 as a rhoptry-neck protein that relocalizes to the moving junction.
moving junction	supports	host cell invasion	`DOI:10.1371/journal.ppat.0010017` Alexander et al. 2005 studied the moving junction complex in invading Toxoplasma tachyzoites.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral groundings for rhoptry neck protein cohorts. RON proteins are grouped by rhoptry-neck localization in this first substructure record, but the cohort contains multiple unrelated effector families.

Evidence

GO:1990225 Gene Ontology cellular-component term for the rhoptry neck.
PMID:16002398 Bradley et al. 2005, Proteomic analysis of rhoptry organelles reveals many novel constituents for host-parasite interactions in Toxoplasma gondii, Journal of Biological Chemistry.
DOI:10.1371/journal.ppat.0010017 Alexander et al. 2005, Identification of the moving junction complex of Toxoplasma gondii: a collaboration between distinct secretory organelles, PLOS Pathogens.
DOI:10.1038/nrmicro1800 Boothroyd and Dubremetz 2008, Kiss and spit: the dual roles of Toxoplasma rhoptries, Nature Reviews Microbiology.
DOI:10.1128/mmbr.00197-22 Waller and Carruthers 2024, Adaptations and metabolic evolution of myzozoan protists across diverse lifestyles and environments, Microbiology and Molecular Biology Reviews.

Curation history

2026-09-13T12:00:13Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-13T12:01:09Z codex · EXPANDED_RECORD — Added rhoptry parthood, a label-only rhoptry neck protein component, Apicomplexa and Toxoplasma gondii scope, secretion and moving-junction functions, GO/DOI evidence, a nonmechanistic RON export graph, and a RON grounding TODO.
2026-09-21T13:14:52Z codex · REPLACED_UNREADABLE_EVIDENCE — Replaced Bradley et al. 2005 DOI citations with PMID:16002398 so rhoptry-neck proteome evidence resolves through PubMed.

Source: data/structures/membrane_organelle/rhoptry_neck.yaml