methionine-importing ABC transporter complex

GO:1990197 · Other · Multiprotein complex · Proposed

An ATP-binding cassette (ABC) transporter complex that is capable of methionine-importing activity. An example is the bacterial MetNIQ methionine transporter, that consists of the dimeric ATPase subunit MetN located at the cytoplasmic side of the plasma membrane and the dimeric transmembrane subunit MetI. MetQ is regarded as the periplasmic methionine-binding chaperon subunit, and is capable of transporting methionine from the periplasm into the cytoplasm in an ATP-dependent manner. [GO:1990197]

Synonyms: ATP-binding cassette (ABC) methionine importer complex; ATP-dependent methionine importer complex; ATP-dependent methionine importing complex; ATP-dependent methionine-importing complex; MetNI complex; MetNIQ complex; MetNIQ transport complex; MetNI transport complex; MetNI transporter 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
ABC transporter, methionine import, ATP-binding protein MetN, proteobacteria	Protein	part of	`InterPro:IPR012692`	metN, abc	2 copies per E. coli MetNIQ complex in PDB:6CVL	UNKNOWN	Cytoplasmic ATP-binding subunit of the E. coli MetNIQ methionine ABC importer. `GO:1990197` GO:1990197 defines the bacterial MetNIQ example as containing a dimeric ATPase MetN subunit. `InterPro:IPR012692` InterPro IPR012692 is the proteobacterial methionine ABC transporter ATP-binding protein MetN family. `PDB:6CVL` PDB:6CVL contains two MetN nucleotide-binding subunits from E. coli K-12.
MetI transmembrane subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	metI, yaeE	2 copies per E. coli MetNIQ complex in PDB:6CVL	UNKNOWN	Integral membrane permease subunit that forms the MetNIQ translocation path with a second MetI copy. `GO:1990197` GO:1990197 defines the bacterial MetNIQ example as containing a dimeric transmembrane subunit MetI. `PDB:6CVL` PDB:6CVL contains two MetI transmembrane subunits from E. coli K-12.
MetQ periplasmic methionine-binding protein	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	metQ, yaeC	1 copy per E. coli MetNIQ complex in PDB:6CVL	UNKNOWN	Periplasmic binding-protein subunit that docks on MetNI and delivers methionine to the transporter. `GO:1990197` GO:1990197 defines MetQ as the periplasmic methionine-binding chaperon subunit in the bacterial MetNIQ example. `PDB:6CVL` PDB:6CVL contains one MetQ periplasmic binding protein from E. coli K-12.

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.

ABC transporter, methionine import, ATP-binding protein MetN, proteobacteria

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P30750`	Methionine import ATP-binding protein MetN	metN	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (2 references) Reviewed E. coli K-12 MetN accession that UniProt maps to GO:1990197 and RCSB maps to the two MetN copies in PDB:6CVL entity 1. `UniProtKB:P30750` UniProtKB P30750 is the reviewed E. coli K-12 entry for Methionine import ATP-binding protein MetN. `PDB:6CVL` RCSB maps PDB:6CVL entity 1 to UniProtKB:P30750 and reports two MetN molecules in the assembly.

MetI transmembrane subunit

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P31547`	D-methionine transport system permease protein MetI	metI	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (2 references) Reviewed E. coli K-12 MetI accession that UniProt maps to GO:1990197 and RCSB maps to the two MetI copies in PDB:6CVL entity 2. `UniProtKB:P31547` UniProtKB P31547 is the reviewed E. coli K-12 entry for the D-methionine transport system permease MetI. `PDB:6CVL` RCSB maps PDB:6CVL entity 2 to UniProtKB:P31547 and reports two MetI molecules in the assembly.

MetQ periplasmic methionine-binding protein

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P28635`	D-methionine-binding lipoprotein MetQ	metQ	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (2 references) Reviewed E. coli K-12 MetQ accession that UniProt maps to GO:1990197 and RCSB maps to the single MetQ copy in PDB:6CVL entity 3. `UniProtKB:P28635` UniProtKB P28635 is the reviewed E. coli K-12 entry for the D-methionine-binding lipoprotein MetQ. `PDB:6CVL` RCSB maps PDB:6CVL entity 3 to UniProtKB:P28635 and reports one MetQ molecule in the assembly.

Canonical examples

NCBITaxon:83333 Escherichia coli K-12 — E. coli K-12 source of the MetN2I2Q methionine ABC importer deposited as PDB:6CVL. [PDB:6CVL]

Functions

ABC-type D-methionine transporter activity GO:0033232 — MetNI couples ATP hydrolysis to transport of D-methionine and methionine derivatives across the plasma membrane.
- GO:0033232 GO:0033232 is the Gene Ontology molecular-function term for ABC-type D-methionine transporter activity.
- DOI:10.1073/pnas.1811003115 Nguyen et al. 2018 characterized D-methionine derivative transport by the E. coli MetNI transporter and solved the PDB:6CVL MetNIQ structure.
L-methionine transmembrane transporter activity GO:0015191 — MetNIQ imports L-methionine across the bacterial plasma membrane through an ATP-binding-cassette mechanism.
- GO:1990197 GO:1990197 defines the complex by methionine-importing activity.
- GO:0015191 GO:0015191 is the Gene Ontology molecular-function term for L-methionine transmembrane transporter activity.
- PMID:22095702 Johnson et al. 2012 analyzed inward-facing E. coli MetNI methionine ABC transporter structures.

Physical properties

SUBUNIT_COUNT: 5 (E. coli MetN2I2Q complex in PDB:6CVL biological assembly 1) [PDB:6CVL]

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral family groundings for MetI transmembrane subunits and MetQ periplasmic methionine-binding proteins. The first record uses reviewed labels for MetI and MetQ rather than forcing the MetI component into a generic amino-acid ABC permease/domain entry or the MetQ component into the broader NlpA lipoprotein family.

Evidence

GO:1990197 Gene Ontology cellular-component term for the methionine-importing ABC transporter complex and source of ATP-dependent and MetNI/MetNIQ synonymy.
GO:1902495 QuickGO reports GO:1902495 transmembrane transporter complex in the ancestor set of GO:1990197.
GO:0033232 Gene Ontology molecular-function term for ABC-type D-methionine transporter activity.
GO:0015191 Gene Ontology molecular-function term for L-methionine transmembrane transporter activity.
InterPro:IPR012692 InterPro family entry for proteobacterial methionine-import ATP-binding protein MetN.
UniProtKB:P30750 Reviewed E. coli K-12 MetN ATP-binding protein entry.
UniProtKB:P31547 Reviewed E. coli K-12 MetI permease protein entry.
UniProtKB:P28635 Reviewed E. coli K-12 MetQ methionine-binding protein entry.
PDB:6CVL RCSB Protein Data Bank entry for the E. coli K-12 MetN2I2Q methionine ABC transporter complex.
PMID:22095702 PubMed identifier for Johnson, Nguyen, Yeates and Rees 2012, the Protein Science MetNI conformational paper cited in the GO:1990197 definition.
DOI:10.1002/pro.765 DOI for Johnson et al. 2012, Inward facing conformations of the MetNI methionine ABC transporter.
PMID:30352853 PubMed identifier for Nguyen et al. 2018, the PNAS paper describing the PDB:6CVL MetNIQ structure.
DOI:10.1073/pnas.1811003115 DOI for Nguyen et al. 2018, Noncanonical role for the binding protein in substrate uptake by the MetNI methionine ATP Binding Cassette transporter.

Curation history

2026-10-01T22:43:44Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-10-01T22:45:04Z codex · EXPANDED_RECORD — Added GO synonymy and transmembrane-transporter parentage, the E. coli MetN, MetI, and MetQ constituents with reviewed UniProt examples, the PDB-backed E. coli MetNIQ canonical example, L- and D-methionine transporter activities, 2:2:1 stoichiometry, component-grounding follow-up, and DOI/PMID/PDB evidence.
2026-10-01T22:45:32Z codex · REFINED_EVIDENCE — Corrected the GO:1902495 parentage note to describe GO:1902495 as an ancestor of GO:1990197.

Source: data/structures/other/methionine_importing_abc_transporter_complex.yaml