Toc complex

GO:0010006 · Other · Multiprotein complex · Proposed

A chloroplast outer-envelope protein translocon complex that forms the outer-membrane step of nuclear-encoded preprotein import into the chloroplast. [GO:0010006]

Synonyms: TOC complex

Part of: chloroplast outer membrane (GO:0009707)

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

Taxonomic distribution

NCBITaxon:3055 Chlamydomonas reinhardtii — COMMON: Chlamydomonas reinhardtii has a Toc complex in the chloroplast outer envelope that couples with the inner envelope Tic complex in a resolved TOC-TIC import supercomplex. [DOI:10.1016/j.cell.2022.10.030]

Canonical examples

NCBITaxon:3055 Chlamydomonas reinhardtii — Green-algal model in which a chloroplast TOC-TIC supercomplex spanning both envelope membranes was resolved structurally. [DOI:10.1016/j.cell.2022.10.030]

Functions

protein import into chloroplast stroma GO:0045037 — The Toc complex contributes the outer-envelope step of nuclear-encoded preprotein import toward the chloroplast stroma.
- GO:0045037 GO:0045037 defines protein import into the chloroplast stroma.
- DOI:10.1016/j.cell.2022.10.030 Jin et al. 2022 resolved the Toc portion of a Chlamydomonas TOC-TIC supercomplex spanning the chloroplast envelope.

Mechanism graphs

Toc contributes the outer-envelope import step (FUNCTION)

In Chlamydomonas, the Toc complex resides in the chloroplast outer membrane and couples with the inner-envelope Tic complex during stromal preprotein import.

Subject	Predicate	Object	Evidence
Toc complex	is part of	chloroplast outer membrane	`GO:0010006` GO:0010006 defines the Toc complex as a protein translocon at the chloroplast outer membrane.
Toc complex	couples with	Tic complex	`DOI:10.1016/j.cell.2022.10.030` Jin et al. 2022 resolved a Chlamydomonas TOC-TIC supercomplex spanning the two chloroplast envelope membranes.
Toc complex	routes precursors toward	protein import into chloroplast stroma	`DOI:10.1016/j.cell.2022.10.030` Jin et al. 2022 resolved an outer-envelope Toc portion in a chloroplast protein-import supercomplex.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral component groundings for Toc75-channel and Toc-receptor subfamilies before adding subunit-level component rows to this source-neutral Toc record. GO exactly grounds the Toc complex itself, but this record does not assert component-family CURIEs for individual Toc subunits until those families have been curated.

Evidence

GO:0010006 Gene Ontology cellular-component term for the Toc complex.
GO:0032991 Gene Ontology cellular-component term for a protein-containing complex.
GO:0009707 Gene Ontology cellular-component term for the chloroplast outer membrane that carries the Toc complex.
GO:0009941 Gene Ontology cellular-component term for the chloroplast envelope containing the Toc-bearing outer membrane.
GO:0031897 Gene Ontology cellular-component term for the Tic complex, the inner-envelope partner of Toc in stromal preprotein import.
GO:0045037 Gene Ontology biological-process term for protein import into the chloroplast stroma.
DOI:10.1016/j.cell.2022.10.030 Jin et al. 2022, Structure of a TOC-TIC supercomplex spanning two chloroplast envelope membranes, Cell.

Curation history

2026-09-13T03:58:02Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-13T03:58:34Z codex · EXPANDED_RECORD — Added TOC synonymy, protein-complex parentage, chloroplast outer-membrane parthood, Chlamydomonas scope, stromal protein-import function, GO and Jin 2022 evidence, a nonmechanistic Toc/Tic import graph, and a Toc-subunit boundary TODO.
2026-09-13T04:08:58Z codex · ADDRESS_REVIEW — Resolved #748 by narrowing the Toc subunit-boundary TODO and graph scope note to avoid an uncited plant-versus-green-alga composition claim.

Source: data/structures/other/toc_complex.yaml