PotABCD spermidine ABC transporter complex

cellstructuremech:potabcd_spermidine_abc_transporter_complex · Other · Multiprotein complex · Proposed

An Escherichia coli PotABCD ATP-binding cassette importer composed of two PotA ATP-binding subunits, one PotB permease, one PotC permease, and one PotD periplasmic substrate-binding protein that imports spermidine and can also import putrescine. [ComplexPortal:CPX-4383]

Synonyms: Spermidine ABC transporter complex; Spermidine-preferential ABC transporter complex; potABCD complex

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
Spermidine/putrescine import ATP-binding protein PotA	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	potA	2 copies in the E. coli K-12 Complex Portal CPX-4383 entry	ESSENTIAL	Cytoplasmic nucleotide-binding subunit that dimerizes as two copies and hydrolyzes ATP to power PotBC channel cycling. `ComplexPortal:CPX-4383` Complex Portal CPX-4383 curates two P69874/PotA copies in the E. coli K-12 PotABCD spermidine ABC transporter complex. `UniProtKB:P69874` UniProtKB P69874 is the reviewed E. coli K-12 entry for Spermidine/putrescine import ATP-binding protein PotA.
Spermidine/putrescine transport system permease protein PotB	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	potB	1 copy in the E. coli K-12 Complex Portal CPX-4383 entry	ESSENTIAL	Inner-membrane permease subunit that pairs with PotC to form the polyamine translocation channel. `ComplexPortal:CPX-4383` Complex Portal CPX-4383 curates one P0AFK4/PotB copy in the E. coli K-12 PotABCD spermidine ABC transporter complex. `UniProtKB:P0AFK4` UniProtKB P0AFK4 is the reviewed E. coli K-12 entry for Spermidine/putrescine transport system permease protein PotB.
Spermidine/putrescine transport system permease protein PotC	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	potC	1 copy in the E. coli K-12 Complex Portal CPX-4383 entry	ESSENTIAL	Inner-membrane permease subunit that pairs with PotB to form the polyamine translocation channel. `ComplexPortal:CPX-4383` Complex Portal CPX-4383 curates one P0AFK6/PotC copy in the E. coli K-12 PotABCD spermidine ABC transporter complex. `UniProtKB:P0AFK6` UniProtKB P0AFK6 is the reviewed E. coli K-12 entry for Spermidine/putrescine transport system permease protein PotC.
Spermidine/putrescine-binding periplasmic protein PotD	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	potD	1 copy in the E. coli K-12 Complex Portal CPX-4383 entry	ESSENTIAL	Periplasmic substrate-binding subunit that delivers bound spermidine or putrescine to the PotBC permease. `ComplexPortal:CPX-4383` Complex Portal CPX-4383 curates one P0AFK9/PotD copy in the E. coli K-12 PotABCD spermidine ABC transporter complex. `UniProtKB:P0AFK9` UniProtKB P0AFK9 is the reviewed E. coli K-12 entry for Spermidine/putrescine-binding periplasmic protein.

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.

Spermidine/putrescine import ATP-binding protein PotA

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P69874`	Spermidine/putrescine import ATP-binding protein PotA	potA	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) `UniProtKB:P69874` Reviewed Swiss-Prot entry POTA_ECOLI is the E. coli K-12 PotA accession and cross-references ComplexPortal:CPX-4383.

Spermidine/putrescine transport system permease protein PotB

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P0AFK4`	Spermidine/putrescine transport system permease protein PotB	potB	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) `UniProtKB:P0AFK4` Reviewed Swiss-Prot entry POTB_ECOLI is the E. coli K-12 PotB accession and cross-references ComplexPortal:CPX-4383.

Spermidine/putrescine transport system permease protein PotC

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P0AFK6`	Spermidine/putrescine transport system permease protein PotC	potC	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) `UniProtKB:P0AFK6` Reviewed Swiss-Prot entry POTC_ECOLI is the E. coli K-12 PotC accession and cross-references ComplexPortal:CPX-4383.

Spermidine/putrescine-binding periplasmic protein PotD

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P0AFK9`	Spermidine/putrescine-binding periplasmic protein	potD	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) `UniProtKB:P0AFK9` Reviewed Swiss-Prot entry POTD_ECOLI is the E. coli K-12 PotD accession and cross-references ComplexPortal:CPX-4383.

Source composition assertions

Spermidine ABC transporter complex (ComplexPortal:CPX-4383)

Escherichia coli (strain K12) (NCBITaxon:83333) · Heteropentamer · ECO:0005547 · retrieved 2026-10-02

Participant	Source type	Source name	Stoichiometry
`UniProtKB:P69874` — Spermidine/putrescine import ATP-binding protein PotA	protein	potA	2
`UniProtKB:P0AFK4` — Spermidine/putrescine transport system permease protein PotB	protein	potB	1
`UniProtKB:P0AFK6` — Spermidine/putrescine transport system permease protein PotC	protein	potC	1
`UniProtKB:P0AFK9` — Spermidine/putrescine-binding periplasmic protein	protein	potD	1

Curator-scoped import: E. coli K-12 PotABCD spermidine ABC transporter source composition for this record. Source evidence: inferred by curator. The accession was resolved through the Complex Portal accession endpoint; no equivalence xref was inferred.

Canonical examples

NCBITaxon:83333 Escherichia coli K-12 — Source strain for Complex Portal CPX-4383, which curates the heteropentameric PotA2BCD spermidine ABC transporter composition. [ComplexPortal:CPX-4383]

Functions

ABC-type polyamine transporter activity GO:0015417 — The PotABCD importer couples PotA ATP hydrolysis to uptake of extracellular polyamines through the PotB/PotC inner-membrane channel.
- GO:0015417 GO:0015417 is the molecular-function term for ABC-type polyamine transporter activity.
- ComplexPortal:CPX-4383 Complex Portal cross-references GO:0015417 for the E. coli K-12 PotABCD complex.
ABC-type putrescine transporter activity GO:0015594 — PotABCD can also import putrescine by an ATP-dependent ABC-transporter reaction.
- GO:0015594 GO:0015594 is the molecular-function term for ABC-type putrescine transporter activity.
- ComplexPortal:CPX-4383 Complex Portal cross-references GO:0015594 for the E. coli K-12 PotABCD complex.

Physical properties

SUBUNIT_COUNT: 5 (E. coli K-12 PotA2BCD heteropentamer in ComplexPortal:CPX-4383) [ComplexPortal:CPX-4383]

Mechanism graphs

PotABCD imports polyamines through an ABC-transporter core (FUNCTION)

PotD, PotB, PotC, and two PotA copies form an E. coli substrate-binding-protein ABC importer for spermidine and putrescine.

Subject	Predicate	Object	Evidence
Spermidine/putrescine-binding periplasmic protein PotD	delivers substrate to	Spermidine/putrescine transport system permease protein PotB	`ComplexPortal:CPX-4383` CPX-4383 curates PotD, PotB, and PotC as participants in the E. coli K-12 spermidine ABC transporter complex.
Spermidine/putrescine-binding periplasmic protein PotD	delivers substrate to	Spermidine/putrescine transport system permease protein PotC	`ComplexPortal:CPX-4383` CPX-4383 curates PotD, PotB, and PotC as participants in the E. coli K-12 spermidine ABC transporter complex.
Spermidine/putrescine import ATP-binding protein PotA	powers	ABC-type polyamine transporter activity	`ComplexPortal:CPX-4383` CPX-4383 curates PotA as two copies in a complex annotated with GO:0015417.
Spermidine/putrescine transport system permease protein PotB	forms channel with	Spermidine/putrescine transport system permease protein PotC	`ComplexPortal:CPX-4383` CPX-4383 curates PotB and PotC as one copy each in the E. coli K-12 spermidine ABC transporter complex.
PotABCD spermidine ABC transporter complex	enables	ABC-type polyamine transporter activity	`ComplexPortal:CPX-4383` Complex Portal cross-references GO:0015417 for the E. coli K-12 PotABCD complex.
PotABCD spermidine ABC transporter complex	enables	ABC-type putrescine transporter activity	`ComplexPortal:CPX-4383` Complex Portal cross-references GO:0015594 for the E. coli K-12 PotABCD complex.
ABC-type polyamine transporter activity	moves	periplasmic polyamine	`GO:0015417` GO:0015417 defines ATP-dependent ABC-type polyamine import from outside to inside.
ABC-type polyamine transporter activity	targets	cytoplasmic polyamine	`GO:0015417` GO:0015417 states the outside-to-inside polyamine ABC-transporter reaction.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral protein-family groundings for PotA, PotB, PotC, and PotD before replacing their reviewed-label-only component rows. ComplexPortal:CPX-4383 and the reviewed E. coli K-12 UniProt records exactly identify the four PotABCD proteins, but no InterPro, Pfam, NCBIfam, or GO accession was verified as an exact source-neutral family for each named constituent.

Evidence

ComplexPortal:CPX-4383 Complex Portal entry for the E. coli K-12 Spermidine ABC transporter complex, systematic name 2xpotA:potB:potC:potD.
GO:0055052 Gene Ontology cellular-component parent term for ABC transporter complexes that contain a substrate-binding subunit.
GO:0015417 Gene Ontology molecular-function term for ABC-type polyamine transporter activity.
GO:0015594 Gene Ontology molecular-function term for ABC-type putrescine transporter activity.
UniProtKB:P69874 Reviewed E. coli K-12 PotA ATP-binding protein entry.
UniProtKB:P0AFK4 Reviewed E. coli K-12 PotB permease protein entry.
UniProtKB:P0AFK6 Reviewed E. coli K-12 PotC permease protein entry.
UniProtKB:P0AFK9 Reviewed E. coli K-12 PotD spermidine/putrescine-binding periplasmic protein entry.
PMID:18634750 PubMed identifier for Moussatova et al. 2008, ATP-binding cassette transporters in Escherichia coli.
DOI:10.1016/j.bbamem.2008.06.009 DOI for Moussatova et al. 2008, ATP-binding cassette transporters in Escherichia coli.
PMID:11421274 PubMed identifier for Igarashi and Kashiwagi 2001, Polyamine uptake systems in Escherichia coli.
DOI:10.1016/s0923-2508(01)01198-6 DOI for Igarashi and Kashiwagi 2001, Polyamine uptake systems in Escherichia coli.

Curation history

2026-10-02T08:28:36Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-10-02T08:30:22Z codex · EXPANDED_RECORD — Added Complex Portal and GO synonymy, ABC transporter parentage, PotA, PotB, PotC, and PotD component rows with E. coli K-12 reviewed UniProt examples, ABC-type polyamine and putrescine transporter activities, a compact function graph, CPX-4383 heteropentamer source composition, and a component-family grounding TODO.

Source: data/structures/other/potabcd_spermidine_abc_transporter_complex.yaml