MlaFEDB lipid transport complex

cellstructuremech:mlafedb_lipid_transport_complex · Other · Multiprotein complex · Proposed

An Escherichia coli inner-membrane ABC transporter complex composed of MlaE, MlaF, MlaD, and MlaB subunits that participates in phospholipid transport during maintenance of outer-membrane lipid asymmetry. [ComplexPortal:CPX-3464]

Synonyms: MlaFEDB 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
Intermembrane phospholipid transport system permease protein MlaE	Protein	part of	`InterPro:IPR053408`	mlaE	2 copies in E. coli PDB:7CGE assembly 1	ESSENTIAL	Inner-membrane permease constituent that contributes two copies to the transmembrane core of the MlaFEDB complex. `ComplexPortal:CPX-3464` Complex Portal CPX-3464 curates P64606/MlaE as an E. coli K-12 MlaFEDB lipid transport complex participant. `UniProtKB:P64606` UniProtKB P64606 is the reviewed E. coli K-12 entry for Intermembrane phospholipid transport system permease protein MlaE. `InterPro:IPR053408` InterPro IPR053408 is the MlaE Permease family entry. `PDB:7CGE` RCSB maps two PDB:7CGE MlaE chains to UniProtKB:P64606 in the author-defined E. coli MlaFEDB assembly.
Intermembrane phospholipid transport system ATP-binding protein MlaF	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	mlaF	2 copies in E. coli PDB:7CGE assembly 1	ESSENTIAL	Cytoplasmic ATP-binding constituent that contributes two nucleotide-binding copies to the MlaFEDB ABC-transporter core. `ComplexPortal:CPX-3464` Complex Portal CPX-3464 curates P63386/MlaF as an E. coli K-12 MlaFEDB lipid transport complex participant. `UniProtKB:P63386` UniProtKB P63386 is the reviewed E. coli K-12 entry for Intermembrane phospholipid transport system ATP-binding protein MlaF. `PDB:7CGE` RCSB maps two PDB:7CGE MlaF chains to UniProtKB:P63386 in the author-defined E. coli MlaFEDB assembly.
Intermembrane phospholipid transport system binding protein MlaD	Protein	part of	`InterPro:IPR030970`	mlaD	6 copies in the E. coli K-12 Complex Portal CPX-3464 entry and PDB:7CGE assembly 1	ESSENTIAL	MlaFEDB binding-protein constituent that forms the six-copy periplasmic MlaD ring in the E. coli inner-membrane complex. `ComplexPortal:CPX-3464` Complex Portal CPX-3464 curates six P64604/MlaD copies in the E. coli K-12 MlaFEDB lipid transport complex. `UniProtKB:P64604` UniProtKB P64604 is the reviewed E. coli K-12 entry for Intermembrane phospholipid transport system binding protein MlaD. `InterPro:IPR030970` InterPro IPR030970 is the Probable phospholipid ABC transporter-binding protein MlaD family entry. `PDB:7CGE` RCSB maps six PDB:7CGE MlaD chains to UniProtKB:P64604 in the author-defined E. coli MlaFEDB assembly.
Intermembrane phospholipid transport system binding protein MlaB	Protein	part of	`InterPro:IPR049743`	mlaB	2 copies in E. coli PDB:7CGE assembly 1	ESSENTIAL	Cytoplasmic accessory constituent paired with MlaF in the MlaFEDB lipid transport complex. `ComplexPortal:CPX-3464` Complex Portal CPX-3464 curates P64602/MlaB as an E. coli K-12 MlaFEDB lipid transport complex participant. `UniProtKB:P64602` UniProtKB P64602 is the reviewed E. coli K-12 entry for Intermembrane phospholipid transport system binding protein MlaB. `InterPro:IPR049743` InterPro IPR049743 is the Intermembrane phospholipid transport system binding protein MlaB family entry. `PDB:7CGE` RCSB maps two PDB:7CGE MlaB chains to UniProtKB:P64602 in the author-defined E. coli MlaFEDB assembly.

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.

Intermembrane phospholipid transport system permease protein MlaE

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P64606`	Intermembrane phospholipid transport system permease protein MlaE	mlaE	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) `UniProtKB:P64606` Reviewed Swiss-Prot entry MLAE_ECOLI is the E. coli K-12 MlaE accession and cross-references ComplexPortal:CPX-3464 and PDB:7CGE.

Intermembrane phospholipid transport system ATP-binding protein MlaF

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P63386`	Intermembrane phospholipid transport system ATP-binding protein MlaF	mlaF	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) `UniProtKB:P63386` Reviewed Swiss-Prot entry MLAF_ECOLI is the E. coli K-12 MlaF accession and cross-references ComplexPortal:CPX-3464 and PDB:7CGE.

Intermembrane phospholipid transport system binding protein MlaD

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P64604`	Intermembrane phospholipid transport system binding protein MlaD	mlaD	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) `UniProtKB:P64604` Reviewed Swiss-Prot entry MLAD_ECOLI is the E. coli K-12 MlaD accession and cross-references ComplexPortal:CPX-3464 and PDB:7CGE.

Intermembrane phospholipid transport system binding protein MlaB

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P64602`	Intermembrane phospholipid transport system binding protein MlaB	mlaB	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) `UniProtKB:P64602` Reviewed Swiss-Prot entry MLAB_ECOLI is the E. coli K-12 MlaB accession and cross-references ComplexPortal:CPX-3464 and PDB:7CGE.

Source composition assertions

MlaFEDB lipid transport complex (ComplexPortal:CPX-3464)

Escherichia coli (strain K12) (NCBITaxon:83333) · ECO:0000353 · retrieved 2026-10-02

Participant	Source type	Source name	Stoichiometry
`UniProtKB:P64606` — Intermembrane phospholipid transport system permease protein MlaE	protein	mlaE	not asserted
`UniProtKB:P63386` — Intermembrane phospholipid transport system ATP-binding protein MlaF	protein	mlaF	not asserted
`UniProtKB:P64604` — Intermembrane phospholipid transport system binding protein MlaD	protein	mlaD	6
`UniProtKB:P64602` — Intermembrane phospholipid transport system binding protein MlaB	protein	mlaB	not asserted

Curator-scoped import: E. coli K-12 MlaFEDB source composition for this record. Source evidence: physical interaction evidence. 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-3464 and for PDB:7CGE, an author-defined dodecameric MlaFEDB electron-microscopy assembly with two MlaE, two MlaF, six MlaD, and two MlaB chains. [PDB:7CGE]

Functions

phospholipid transport GO:0015914 — MlaFEDB participates in ATP-dependent phospholipid transport as part of the Mla envelope system that maintains outer-membrane lipid asymmetry.
- GO:0015914 GO:0015914 is the biological-process term for phospholipid transport.
- ComplexPortal:CPX-3464 Complex Portal cross-references phospholipid transport on the E. coli K-12 MlaFEDB lipid transport complex and describes ATP hydrolysis during MlaC-to-MlaFEDB phospholipid handoff.

Physical properties

SUBUNIT_COUNT: 12 (PDB:7CGE author-defined dodecameric MlaFEDB assembly 1) [PDB:7CGE]

Mechanism graphs

MlaFEDB participates in phospholipid transport (FUNCTION)

MlaE, MlaF, MlaD, and MlaB form the MlaFEDB inner-membrane ABC transporter that receives MlaC phospholipid substrates in the Mla outer-membrane lipid-asymmetry system.

Subject	Predicate	Object	Evidence
Intermembrane phospholipid transport system permease protein MlaE	assembles with	Intermembrane phospholipid transport system ATP-binding protein MlaF	`ComplexPortal:CPX-3464` CPX-3464 curates MlaE and MlaF as participants in the E. coli MlaFEDB lipid transport complex.
Intermembrane phospholipid transport system binding protein MlaD	forms hexameric ring in	MlaFEDB lipid transport complex	`ComplexPortal:CPX-3464` CPX-3464 curates six MlaD copies. `PDB:7CGE` RCSB maps chains G-L of PDB:7CGE to MlaD UniProtKB:P64604.
Intermembrane phospholipid transport system binding protein MlaB	assembles with	Intermembrane phospholipid transport system ATP-binding protein MlaF	`PDB:7CGE` RCSB maps PDB:7CGE chains C and F to MlaB and chains B and E to MlaF.
Intermembrane phospholipid transport system MlaC	delivers phospholipids to	MlaFEDB lipid transport complex	`ComplexPortal:CPX-3464` CPX-3464 describes MlaC shuttling phospholipid substrates between the inner-membrane MlaFEDB transporter and an outer-membrane complex.
MlaFEDB lipid transport complex	enables	phospholipid transport	`ComplexPortal:CPX-3464` Complex Portal cross-references GO:0015914 on the E. coli K-12 MlaFEDB lipid transport complex.

Discussions

CURATION_TODO (OPEN): Resolve an exact source-neutral MlaF protein family before replacing its reviewed-label-only component row. ComplexPortal:CPX-3464, PDB:7CGE, and the reviewed E. coli K-12 UniProt record exactly identify MlaF, but its UniProt InterPro cross-references are broad ABC-transporter, AAA+ ATPase, ABC-transporter signature, and P-loop NTPase entries rather than an exact MlaF family.
INTERPRETATION (RESOLVED): Should MlaC or the outer-membrane Mla complex be curated as constituents of the MlaFEDB lipid transport complex? MlaC shuttles phospholipid substrates between the outer-membrane Mla machinery and the inner-membrane MlaFEDB transporter, but ComplexPortal:CPX-3464 scopes the MlaFEDB complex itself to MlaE, MlaF, MlaD, and MlaB.

Evidence

ComplexPortal:CPX-3464 Complex Portal entry for the E. coli K-12 MlaFEDB lipid transport complex, systematic name mlaB:mlaD:mlaE:mlaF.
GO:0043190 Gene Ontology cellular-component parent term for ATP-binding cassette transporter complexes.
GO:0015914 Gene Ontology biological-process term for phospholipid transport.
InterPro:IPR053408 InterPro family entry for MlaE Permease.
InterPro:IPR030970 InterPro family entry for Probable phospholipid ABC transporter-binding protein MlaD.
InterPro:IPR049743 InterPro family entry for Intermembrane phospholipid transport system binding protein MlaB.
UniProtKB:P64606 Reviewed E. coli K-12 MlaE UniProtKB entry.
UniProtKB:P63386 Reviewed E. coli K-12 MlaF UniProtKB entry.
UniProtKB:P64604 Reviewed E. coli K-12 MlaD UniProtKB entry.
UniProtKB:P64602 Reviewed E. coli K-12 MlaB UniProtKB entry.
PDB:7CGE RCSB Protein Data Bank entry for a nucleotide-free E. coli MlaFEDB electron-microscopy structure.
PMID:32884137 PubMed identifier for Chi et al. 2020, Structural mechanism of phospholipids translocation by MlaFEDB complex.
DOI:10.1038/s41422-020-00404-6 DOI for Chi et al. 2020, Structural mechanism of phospholipids translocation by MlaFEDB complex.

Curation history

2026-10-02T12:47:42Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-10-02T12:49:59Z codex · EXPANDED_RECORD — Added ABC transporter parentage, MlaE, MlaF, MlaD, and MlaB component rows with reviewed E. coli K-12 UniProt examples, exact MlaE/MlaD/MlaB InterPro groundings, PDB:7CGE subunit counts, GO phospholipid-transport function, a compact MlaFEDB function graph, and boundary discussions for MlaF grounding plus MlaC and outer-membrane Mla exclusion.
2026-10-02T12:50:47Z complex_portal · ADD_EVIDENCE — Added taxon-specific composition ComplexPortal:CPX-3464 (4 participants); exact accession and taxon verified at import.
2026-10-02T13:04:36Z codex · EDITED_DISCUSSION — Reanchored the MlaC and outer-membrane Mla exclusion discussion from the components section to the four MlaFEDB constituent component rows.

Source: data/structures/other/mlafedb_lipid_transport_complex.yaml