chlorosome envelope

GO:0033105 · Membrane organelle · Other · Proposed

The structure, composed of a monolayer of glycolipids with embedded proteins, that encloses the pigments and other contents of the chlorosome. [GO:0033105]

Synonyms: chlorosome membrane; chlorosomal envelope

Part of: chlorosome (GO:0046858)

Xrefs: uniprot.location:SL-0060 — Chlorosome envelope

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

Components

Component	Type	Part of / acts on	Grounding	Genes	Essential	Role
chlorosome glycolipid monolayer	Lipid	part of	Reviewed label only (reviewed name; no accession asserted)		ESSENTIAL	Asymmetric glycolipid monolayer that encloses the pigment aggregate and contributes the protein-bearing surface of green bacterial chlorosomes. `GO:0033105` GO:0033105 defines the chlorosome envelope as a glycolipid monolayer with embedded proteins. `uniprot.location:SL-0060` — Chlorosome envelope UniProt SL-0060 describes the green-sulfur-bacterial chlorosome envelope as an asymmetric membrane containing galactolipids. `DOI:10.1007/s11120-013-9869-3` Orf and Blankenship 2013 review chlorosomes as bacteriochlorophyll aggregates enclosed by a lipid monolayer whose surface carries chlorosome proteins.
chlorosome baseplate antenna complex	Protein complex	part of	`cellstructuremech:chlorosome_baseplate_antenna_complex`		ESSENTIAL	Bacteriochlorophyll a-CsmA antenna array that sits on one face of the chlorosome envelope and couples interior bacteriochlorophyll aggregates to downstream membrane complexes. `GO:0046858` GO:0046858 defines chlorosomes as attached to the cytoplasmic membrane through a BChl a-containing protein baseplate. `DOI:10.1038/ncomms12454` Nielsen et al. 2016 resolved the in situ CsmA-containing baseplate antenna complex of Chlorobaculum tepidum.
accessory chlorosome envelope proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	csmB, csmC, csmD, csmE, csmF, csmH, csmI, csmJ, csmK, csmX	UNKNOWN	Additional proteins embedded in or attached to the chlorosome envelope surface, with lineage-specific and protein-specific roles in envelope organization. `DOI:10.1128/JB.186.3.646-653.2004` Frigaard et al. 2004 disrupted nine Chlorobium tepidum chlorosome protein genes and analyzed the corresponding chlorosome envelope-protein mutants. `DOI:10.1021/bi060776y` Li et al. 2006 used cross-linking to map molecular contacts among chlorosome envelope proteins from Chlorobium tepidum.

Taxonomic distribution

NCBITaxon:2 Bacteria — VARIABLE: Chlorosome envelopes occur in the chlorosomes of particular anoxygenic green-bacterial phototrophs, including Chlorobi and filamentous Chloroflexota lineages. [DOI:10.1007/s11120-013-9869-3]

Canonical examples

NCBITaxon:1097 Chlorobaculum tepidum — Green sulfur bacterium used to test individual chlorosome envelope protein contributions and to resolve the CsmA baseplate architecture. [DOI:10.1128/JB.186.3.646-653.2004]
NCBITaxon:1108 Chloroflexus aurantiacus — Green filamentous bacterium whose thin chlorosomes were used to visualize the relationship between the CsmA baseplate and the surrounding pigment aggregate. [DOI:10.1128/JB.00690-09]

Functions

photosynthetic light harvesting — The chlorosome envelope organizes the self-assembled bacteriochlorophyll aggregate and a CsmA baseplate so excitation energy can exit the chlorosome toward membrane reaction centers.
- DOI:10.1007/s11120-013-9869-3 Orf and Blankenship 2013 review chlorosome envelopes, baseplates, and bacteriochlorophyll aggregates in the light-harvesting antennae of green photosynthetic bacteria.
- DOI:10.1038/ncomms12454 Nielsen et al. 2016 modeled how the CsmA baseplate transfers excitation energy out of Chlorobaculum tepidum chlorosomes.

Mechanism graphs

Chlorosome envelopes organize pigment-to-baseplate transfer (FUNCTION)

A glycolipid monolayer and embedded chlorosome proteins form the chlorosome envelope around bacteriochlorophyll aggregates, while the CsmA baseplate on one face provides the antenna exit toward membrane reaction-center complexes.

Subject	Predicate	Object	Evidence
chlorosome envelope	is part of	chlorosome	`GO:0033105` GO:0033105 is defined as the structure enclosing the pigments and other contents of a chlorosome.
chlorosome glycolipid monolayer	forms	chlorosome envelope	`uniprot.location:SL-0060` — Chlorosome envelope UniProt SL-0060 describes the envelope as asymmetric and galactolipid-containing.
accessory chlorosome envelope proteins	is embedded in	chlorosome envelope	`DOI:10.1128/JB.186.3.646-653.2004` Frigaard et al. 2004 individually disrupted non-CsmA chlorosome protein genes to test envelope-protein effects on C. tepidum chlorosomes.
chlorosome envelope	encloses	bacteriochlorophyll aggregate	`GO:0033105` GO:0033105 defines the envelope as enclosing the chlorosome pigments and other contents.
CsmA bacteriochlorophyll a baseplate	is positioned on	chlorosome envelope	`DOI:10.1038/ncomms12454` Nielsen et al. 2016 resolved the CsmA baseplate architecture on Chlorobaculum tepidum chlorosomes.
chlorosome envelope	supports	photosynthetic light harvesting	`DOI:10.1007/s11120-013-9869-3` Orf and Blankenship 2013 review chlorosome antenna organization and energy transfer in green photosynthetic bacteria.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral identifiers for the chlorosome glycolipid monolayer and accessory Csm envelope-protein families before replacing the reviewed-label component groundings. The CsmA baseplate is now grounded as a first-class CellStructureMech substructure; this envelope TODO remains for chlorosome-specific lipid chemistry and the non-CsmA envelope proteins rather than asserting approximate ChEBI, InterPro, or Pfam accessions.

Evidence

GO:0033105 Gene Ontology cellular-component term for the chlorosome envelope.
GO:0046858 Gene Ontology cellular-component term for the chlorosome.
uniprot.location:SL-0060 — Chlorosome envelope UniProt Subcellular Location entry that maps chlorosome envelope to GO:0033105.
PMID:14729689 Frigaard, Li, Milks and Bryant 2004, Nine mutants of Chlorobium tepidum each unable to synthesize a different chlorosome protein still assemble functional chlorosomes, Journal of Bacteriology.
DOI:10.1021/bi060776y Li, Frigaard and Bryant 2006, Molecular contacts for chlorosome envelope proteins revealed by cross-linking studies with chlorosomes from Chlorobium tepidum, Biochemistry.
DOI:10.1007/s11120-013-9869-3 Orf and Blankenship 2013, Chlorosome antenna complexes from green photosynthetic bacteria, Photosynthesis Research.
DOI:10.1128/JB.00690-09 Psencik et al. 2009, Structure of chlorosomes from the green filamentous bacterium Chloroflexus aurantiacus, Journal of Bacteriology.
DOI:10.1038/ncomms12454 Nielsen et al. 2016, In situ high-resolution structure of the baseplate antenna complex in Chlorobaculum tepidum, Nature Communications.

Curation history

2026-09-12T14:01:47Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-12T14:02:58Z codex · EXPANDED_RECORD — Added exact GO and UniProt synonymy, chlorosome parthood, the UniProt Subcellular Location xref, glycolipid-monolayer and Csm-protein components, bacterial distribution, Chlorobaculum and Chloroflexus examples, photosynthetic light-harvesting function, DOI/GO/UniProt evidence, a nonmechanistic envelope topology graph, and a component grounding TODO.
2026-09-12T14:06:43Z codex · FIXED_FUNCTION_GROUNDING — Removed broad GO:0015979 photosynthesis grounding from the narrower photosynthetic light-harvesting function while retaining GO:0015979 on the exactly labelled photosynthesis graph node.
2026-09-12T14:14:07Z codex · ADDRESS_REVIEW — Resolved #658 by narrowing the graph endpoint from broad photosynthesis to ungrounded photosynthetic light harvesting; resolved #659 by typing the glycolipid monolayer node as a STRUCTURE.
2026-09-13T07:47:31Z codex · REFINED_RECORD — Grounded the chlorosome-envelope CsmA baseplate component to the newly minted chlorosome baseplate antenna complex record and narrowed the envelope grounding TODO to the glycolipid monolayer and accessory Csm proteins.

Source: data/structures/membrane_organelle/chlorosome_envelope.yaml