phycobilisome

GO:0030089 · Energy complex · Multiprotein complex · Proposed

A membrane-associated light-harvesting pigment-protein complex of cyanobacteria and red algae, built from phycobiliprotein core and rod cylinders plus linker polypeptides, that funnels phycobilin excitation energy to photosynthetic reaction centers. [GO:0030089]

Synonyms: PBS

Part of: thylakoid membrane (GO:0042651)

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
rod phycobiliproteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	cpcA, cpcB, cpeA, cpeB	ESSENTIAL	Pigment-binding alpha and beta subunits that assemble into the peripheral rods and absorb incoming light. `DOI:10.1146/annurev-biophys-062920-063657` Sui 2021 reviews phycobilisome rod architecture and the phycobiliproteins that make rod cylinders. `DOI:10.1038/s41467-022-30962-9` Kawakami et al. 2022 resolved phycocyanin rods in a thermophilic cyanobacterial phycobilisome.
allophycocyanin core cylinders	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	apcA, apcB, apcD, apcF	ESSENTIAL	Core phycobiliproteins that receive excitation from the rods and pass it toward chlorophyll-containing photosystems. `DOI:10.1146/annurev-biophys-062920-063657` Sui 2021 reviews the allophycocyanin core as the central cylinder assembly that receives rod energy. `DOI:10.1038/s41467-021-25813-y` Sauer et al. 2021 resolved the Synechocystis phycobilisome core and its allophycocyanin subunits by cryo-EM.
phycobilisome linker polypeptides	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	cpcC, cpcD, cpcG, apcC, apcE	ESSENTIAL	Internal and terminal linkers organize phycobiliprotein disks, stabilize core and rod geometry, and tune bilin energies along the transfer path. `DOI:10.1146/annurev-biophys-062920-063657` Sui 2021 summarizes rod, core and core-membrane linker roles in phycobilisome assembly and energy transfer. `DOI:10.1038/s41467-022-30962-9` Kawakami et al. 2022 modelled linker positions in the core and rods of a cyanobacterial phycobilisome.
phycobilin chromophores	Small molecule	part of			ESSENTIAL	Linear tetrapyrrole pigments covalently attached to phycobiliproteins; their tuned excitation energies create the directional energy-transfer gradient. `DOI:10.1146/annurev-biophys-062920-063657` Sui 2021 reviews covalent phycobilin attachment and spectral tuning across phycobilisomes.

Organism-specific protein examples

Named proteins in which each component's role was established, with the organism the evidence comes from. The component above is the taxon-agnostic family; these are the specific entries behind it.

rod phycobiliproteins

Accession	Protein	Gene	Organism	Entry
`UniProtKB:Q54715`	C-phycocyanin alpha subunit	cpcA	Synechocystis sp. PCC 6803 substr. Kazusa (`NCBITaxon:1111708`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene cpcA in Synechocystis sp. PCC 6803 substr. Kazusa, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `https://www.uniprot.org/uniprotkb/Q54715` UniProtKB reviewed (Swiss-Prot) entry Q54715, the single reviewed entry for gene cpcA in Synechocystis sp. PCC 6803 substr. Kazusa. Establishes the accession and gene identity only; the component's membership in this structure rests on the record's own sources.
`UniProtKB:Q54714`	C-phycocyanin beta subunit	cpcB	Synechocystis sp. PCC 6803 substr. Kazusa (`NCBITaxon:1111708`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene cpcB in Synechocystis sp. PCC 6803 substr. Kazusa, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `https://www.uniprot.org/uniprotkb/Q54714` UniProtKB reviewed (Swiss-Prot) entry Q54714, the single reviewed entry for gene cpcB in Synechocystis sp. PCC 6803 substr. Kazusa. Establishes the accession and gene identity only; the component's membership in this structure rests on the record's own sources.

allophycocyanin core cylinders

Accession	Protein	Gene	Organism	Entry
`UniProtKB:Q01951`	Allophycocyanin alpha chain	apcA	Synechocystis sp. PCC 6803 substr. Kazusa (`NCBITaxon:1111708`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene apcA in Synechocystis sp. PCC 6803 substr. Kazusa, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `https://www.uniprot.org/uniprotkb/Q01951` UniProtKB reviewed (Swiss-Prot) entry Q01951, the single reviewed entry for gene apcA in Synechocystis sp. PCC 6803 substr. Kazusa. Establishes the accession and gene identity only; the component's membership in this structure rests on the record's own sources.
`UniProtKB:Q01952`	Allophycocyanin beta chain	apcB	Synechocystis sp. PCC 6803 substr. Kazusa (`NCBITaxon:1111708`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene apcB in Synechocystis sp. PCC 6803 substr. Kazusa, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `https://www.uniprot.org/uniprotkb/Q01952` UniProtKB reviewed (Swiss-Prot) entry Q01952, the single reviewed entry for gene apcB in Synechocystis sp. PCC 6803 substr. Kazusa. Establishes the accession and gene identity only; the component's membership in this structure rests on the record's own sources.
`UniProtKB:P72870`	Allophycocyanin subunit alpha-B	apcD	Synechocystis sp. PCC 6803 substr. Kazusa (`NCBITaxon:1111708`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene apcD in Synechocystis sp. PCC 6803 substr. Kazusa, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `https://www.uniprot.org/uniprotkb/P72870` UniProtKB reviewed (Swiss-Prot) entry P72870, the single reviewed entry for gene apcD in Synechocystis sp. PCC 6803 substr. Kazusa. Establishes the accession and gene identity only; the component's membership in this structure rests on the record's own sources.
`UniProtKB:P74551`	Allophycocyanin subunit beta-18	apcF	Synechocystis sp. PCC 6803 substr. Kazusa (`NCBITaxon:1111708`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene apcF in Synechocystis sp. PCC 6803 substr. Kazusa, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `https://www.uniprot.org/uniprotkb/P74551` UniProtKB reviewed (Swiss-Prot) entry P74551, the single reviewed entry for gene apcF in Synechocystis sp. PCC 6803 substr. Kazusa. Establishes the accession and gene identity only; the component's membership in this structure rests on the record's own sources.

phycobilisome linker polypeptides

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P07123`	Phycobilisome 32.1 kDa linker polypeptide, phycocyanin-associated, rod	cpcC	Nostoc sp. PCC 7120 = FACHB-418 (`NCBITaxon:103690`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene cpcC in Nostoc sp. PCC 7120 = FACHB-418, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `PMID:24550276` Watanabe M et al. 2014, ‘Attachment of phycobilisomes in an antenna-photosystem I supercomplex of cyanobacteria.’, Proc Natl Acad Sci U S A. ECO:0000269 experimental evidence cited by UniProt for the 'Cellular thylakoid membrane' localisation of P07123.
`UniProtKB:P73202`	Phycobilisome 8.9 kDa linker polypeptide, phycocyanin-associated, rod	cpcD	Synechocystis sp. PCC 6803 substr. Kazusa (`NCBITaxon:1111708`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene cpcD in Synechocystis sp. PCC 6803 substr. Kazusa, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `https://www.uniprot.org/uniprotkb/P73202` UniProtKB reviewed (Swiss-Prot) entry P73202, the single reviewed entry for gene cpcD in Synechocystis sp. PCC 6803 substr. Kazusa. Establishes the accession and gene identity only; the component's membership in this structure rests on the record's own sources.
`UniProtKB:P73093`	Phycobilisome rod-core linker polypeptide CpcG	cpcG	Synechocystis sp. PCC 6803 substr. Kazusa (`NCBITaxon:1111708`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene cpcG in Synechocystis sp. PCC 6803 substr. Kazusa, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `PMID:17468217` Kondo K et al. 2007, ‘The membrane-associated CpcG2-phycobilisome in Synechocystis: a new photosystem I antenna.’, Plant Physiol. ECO:0000269 experimental evidence cited by UniProt for the 'Cellular thylakoid membrane' localisation of P73093.
`UniProtKB:Q01950`	Phycobilisome 7.8 kDa linker polypeptide, allophycocyanin-associated, core	apcC	Synechocystis sp. PCC 6803 substr. Kazusa (`NCBITaxon:1111708`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene apcC in Synechocystis sp. PCC 6803 substr. Kazusa, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `https://www.uniprot.org/uniprotkb/Q01950` UniProtKB reviewed (Swiss-Prot) entry Q01950, the single reviewed entry for gene apcC in Synechocystis sp. PCC 6803 substr. Kazusa. Establishes the accession and gene identity only; the component's membership in this structure rests on the record's own sources.
`UniProtKB:Q55544`	Phycobiliprotein ApcE	apcE	Synechocystis sp. PCC 6803 substr. Kazusa (`NCBITaxon:1111708`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene apcE in Synechocystis sp. PCC 6803 substr. Kazusa, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `https://www.uniprot.org/uniprotkb/Q55544` UniProtKB reviewed (Swiss-Prot) entry Q55544, the single reviewed entry for gene apcE in Synechocystis sp. PCC 6803 substr. Kazusa. Establishes the accession and gene identity only; the component's membership in this structure rests on the record's own sources.

Taxonomic distribution

NCBITaxon:1117 Cyanobacteriota — COMMON: Cyanobacteria are the bacterial lineage whose thylakoid-associated phycobilisomes supply light to photosystems. [DOI:10.1146/annurev-biophys-062920-063657]
NCBITaxon:2763 Rhodophyta — COMMON: Red algal plastids retain phycobilisomes with the same core-and-rod light-harvesting architecture. [DOI:10.1146/annurev-biophys-062920-063657]

Canonical examples

NCBITaxon:1148 Synechocystis sp. PCC 6803 — Cyanobacterial model used for a cryo-EM structure of the complete phycobilisome in light-harvesting and photoprotected states. [DOI:10.1038/s41467-021-25813-y]
NCBITaxon:32053 Thermostichus vulcanus — Thermophilic cyanobacterium whose phycobilisome core and rods were resolved by cryo-EM. [DOI:10.1038/s41467-022-30962-9]
NCBITaxon:103690 Nostoc sp. PCC 7120 = FACHB-418 — Model for single-particle EM of an intact phycobilisome and phycobilisome-photosystem II assemblies. [DOI:10.1038/cr.2015.59]

Functions

photosynthetic light harvesting — Phycobilisomes absorb visible light through phycobilin-bearing rods and transfer excitation through the allophycocyanin core to photosystem II and, in some states, photosystem I.
- DOI:10.1146/annurev-biophys-062920-063657 Sui 2021 reviews phycobilisome light capture and downhill excitation-energy transfer to photosystems.
photoprotection — Some cyanobacterial phycobilisomes switch to quenched or orange-carotenoid-protein-bound states that dissipate excess absorbed energy.
- DOI:10.1146/annurev-biophys-062920-063657 Sui 2021 reviews phycobilisome quenching and photoprotective states in cyanobacteria.

Mechanism graphs

Rods and linkers funnel bilin excitation through the allophycocyanin core (FUNCTION)

Phycobilins covalently attached to rod phycobiliproteins absorb visible light. Linker proteins order stacked rod and core cylinders so excitation energy moves from rods into the allophycocyanin core and then into chlorophyll-containing photosystems.

Subject	Predicate	Object	Evidence
phycobilin chromophores	are bound by	rod phycobiliproteins	`DOI:10.1146/annurev-biophys-062920-063657` Sui 2021 reviews the bilins carried by rod phycobiliproteins and their role as light absorbers.
rod phycobiliproteins	assemble into	phycobilisome	`DOI:10.1038/s41467-022-30962-9` Kawakami et al. 2022 resolved stacked phycocyanin rods in a cyanobacterial phycobilisome.
allophycocyanin core	forms	phycobilisome	`DOI:10.1038/s41467-021-25813-y` Sauer et al. 2021 resolved the Synechocystis phycobilisome core by cryo-EM.
phycobilisome linker polypeptides	stabilize and tune	phycobilisome	`DOI:10.1038/s41467-022-30962-9` Kawakami et al. 2022 modelled linkers inside phycobiliprotein assemblies of the thermophilic cyanobacterial phycobilisome.
rod phycobiliproteins	transfer excitation to	allophycocyanin core	`DOI:10.1146/annurev-biophys-062920-063657` Sui 2021 describes the rod-to-core direction of excitation-energy transfer through the phycobilisome.
allophycocyanin core	transfers excitation to	chlorophyll photosystems	`DOI:10.1038/s41467-021-25813-y` Sauer et al. 2021 modelled energy transfer through the allophycocyanin core toward photosystem acceptors.
chlorophyll photosystems	perform	photosynthetic light harvesting	`DOI:10.1038/cr.2015.59` Chang et al. 2015 visualized phycobilisomes associated with photosystem II from Nostoc sp. PCC 7120.

Discussions

CURATION_TODO (OPEN): Resolve exact InterPro or Pfam accessions for rod phycobiliprotein, allophycocyanin, linker and phycobilin biosynthetic classes, or split these grouped components where exact family terms exist. The first phycobilisome record avoids broad phycobiliprotein groundings that could blur rods, core subunits and specialized terminal emitters.

Evidence

DOI:10.1146/annurev-biophys-062920-063657 Sui 2021, Structure of Phycobilisomes, Annual Review of Biophysics.
DOI:10.1038/s41467-021-25813-y Sauer et al. 2021, Structural insight into the mechanism of energy transfer in cyanobacterial phycobilisomes, Nature Communications.
DOI:10.1038/s41467-022-30962-9 Kawakami et al. 2022, Core and rod structures of a thermophilic cyanobacterial light-harvesting phycobilisome, Nature Communications.
DOI:10.1038/cr.2015.59 Chang et al. 2015, Structural organization of an intact phycobilisome and its association with photosystem II, Cell Research.

Curation history

2026-09-04T18:36:29Z claude · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-04T18:38:05Z claude · EXPANDED_RECORD — Added phycobilisome synonyms, mereology, components, taxonomy, examples, functions, literature evidence, a rod-core energy-transfer graph, and a protein-family grounding todo.
2026-09-08T07:39:14Z uniprot_genes · SEED_PROTEIN_EXAMPLES — #183: added 11 protein example(s) by resolving each of the component's declared gene symbols to the single reviewed UniProtKB entry for that symbol in a taxon this record names, deduplicated by accession. Symbols resolving to more than one reviewed entry were skipped rather than chosen between.

Source: data/structures/energy_complex/phycobilisome.yaml