Bacterial lipopolysaccharide transport

Reusable module for ATP-driven extraction of lipopolysaccharide (LPS) from the outer leaflet of the inner membrane of diderm bacteria, its transfer across the periplasm along the trans-envelope Lpt protein bridge, and its insertion into the outer leaflet of the outer membrane. The module separates the LptB2FGC inner-membrane extraction machine, the soluble LptA bridge, and the LptD/LptE outer-membrane translocon, which together form the seven-protein lipopolysaccharide transport system.

MODULE:bacterial_lps_transportCOMPLETECONCRETEBiological Processmodules/bacterial_lps_transport.yaml
lipopolysaccharide transportGO:0015920 lipopolysaccharide transport systemGO:0062051
GO:0015920
lipopolysaccharide transport
GO:0015920 grounds movement of LPS from the inner membrane to the cell surface through the trans-envelope Lpt system.
GO:0062051
lipopolysaccharide transport system
GO:0062051 (is_a GO:1990351 transporter complex) is the GO complex term for the whole trans-envelope Lpt machine; its definition cites PMID:29449493.
PMID:22668317
Regulated assembly of the transenvelope protein complex required for lipopolysaccharide export.
Defines the seven essential Lpt proteins and the transenvelope bridge model on which the module's three parts are based.
In Escherichia coli, this LPS transport process is known to require the seven essential Lpt proteins,7 but how these proteins move large, amphipathic LPS molecules across both membranes and the periplasmic space is not understood.
PMID:18424520
Functional analysis of the protein machinery required for transport of lipopolysaccharide to the outer membrane of Escherichia coli.
Places LptA, LptB, LptC, LptD and LptE in one LPS transport machine.
In this paper we provide evidence that LptA, LptB, LptD, LptE, and YrbK (renamed LptC), an essential IM protein characterized here, are all members of the same LPS transport machinery.
PMID:18375759
Identification of two inner-membrane proteins required for the transport of lipopolysaccharide to the outer membrane of Escherichia coli.
Identifies LptF and LptG as the transmembrane subunits of the LptB-energized extraction transporter.
We propose that these two proteins, which we have renamed LptF and LptG, respectively, are the missing transmembrane components of the ABC transporter that, together with LptB, functions to extract LPS from the IM en route to the OM.
KEGG:ppu00540
Pseudomonas putida KT2440 lipopolysaccharide biosynthesis
KEGG ppu00540 includes the P. putida KT2440 Lpt components associated with LPS biogenesis and export, supporting the KT2440 exemplars.

Scope and taxonomy. The Lpt system is present in diderm bacteria that build an LPS outer leaflet: all seven components were defined and characterized in Escherichia coli K-12, and orthologues are found across Proteobacteria and other LPS-bearing phyla (PANTHER reference trees include Chlamydia, Bacteroides, Leptospira, Aquifex and cyanobacteria). The module therefore uses E. coli K-12 as the primary experimental exemplar and Pseudomonas putida KT2440 as a second, independently curated exemplar. It is lineage-specific: monoderm bacteria (Bacillus subtilis), mycobacteria and Rhodococcus, which build mycolate rather than LPS outer layers, and eukaryotes lack the Lpt system, so no members are listed for them. Homologues in diderms without canonical LPS (Deinococcus, Thermotoga) are untested and are discussed in the family reviews. P. putida PP_0982 and PP_0983 encode LptF and LptG but lack lpt gene symbols in UniProt. MsbA flipping of LPS across the inner membrane, LPS biosynthesis, and core/O-antigen assembly are upstream and outside this transport module.

4Nodes
3Parts
0Variant Sets
0Variants
4Annotons
2Connections

Derived QC

Recommended-field compliance

100.0% recommended fields populated

All recommended fields populated.

Module deep research

✗ none found

No MODULE:bacterial_lps_transport deep-research report alongside the module YAML.

Leaf nodes lacking representative members

✓ every leaf node grounds to a representative protein.

Template conformance

✓ every declared conforms_to bundle matches its template motif.

Function consistency and core coverage

8 gene-function check(s) reflected in core functions · 0 conflict(s) · 0 evidence or coverage gap(s) (14 comparison(s))

Retained noncore functions are reported separately; they do not require promotion to core functions. Support from representative genes does not establish conservation across the whole family. Missing reviews or identifiers leave a claim unverified.

AnnotonParticipantFunctionAssessment
lptb2fg_extractor PROTEIN_COMPLEX
Gene 		lipopolysaccharide transfer activity
GO:0140332 		Participant Unchecked
No direct UniProt participant to compare. Abstract selectors and complex-wide activities cannot be inferred from donor or subunit gene reviews.
lptb2fg_extractor/lptb_atpase lptB (Escherichia coli K-12)
UniProtKB:P0A9V1
Family Representative 		ATP hydrolysis activity
GO:0016887 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
lptb2fg_extractor/lptb_atpase lptB (Pseudomonas putida KT2440)
UniProtKB:Q88P99
Family Representative 		ATP hydrolysis activity
GO:0016887 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
lptc_bridge_anchor lptC (Escherichia coli K-12)
UniProtKB:P0ADV9
Family Representative 		lipopolysaccharide transfer activity
GO:0140332 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
lptc_bridge_anchor lptC (Pseudomonas putida KT2440)
UniProtKB:Q88P97
Family Representative 		lipopolysaccharide transfer activity
GO:0140332 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
lpta_bridge lptA (Escherichia coli K-12)
UniProtKB:P0ADV1
Family Representative 		lipopolysaccharide transfer activity
GO:0140332 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
lpta_bridge lptA (Pseudomonas putida KT2440)
UniProtKB:Q88P98
Family Representative 		lipopolysaccharide transfer activity
GO:0140332 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
lptde_translocon PROTEIN_COMPLEX
Gene 		lipopolysaccharide transmembrane transporter activity
GO:0015221 		Participant Unchecked
No direct UniProt participant to compare. Abstract selectors and complex-wide activities cannot be inferred from donor or subunit gene reviews.
lptde_translocon/lpte_plug lptE (Escherichia coli K-12)
UniProtKB:P0ADC1
Family Representative 		lipopolysaccharide binding
GO:0001530 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
lptde_translocon/lpte_plug lptE (Pseudomonas putida KT2440)
UniProtKB:Q88DN0
Family Representative 		lipopolysaccharide binding
GO:0001530 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
lptb_atpase LptB family
PANTHER:PTHR45772:SF10
Family 		ATP hydrolysis activity
GO:0016887 		Family Supported
Family review supports GO:0016887 FAMILY_WIDE. All members are ABC nucleotide-binding domains; ATP hydrolysis is shown directly for LptB and is the shared mechanism of the family.
lptc_bridge_anchor LptC family
PANTHER:PTHR37481
Family 		lipopolysaccharide transfer activity
GO:0140332 		Family Supported
Family review supports GO:0140332 FAMILY_WIDE. The LptC beta-jellyroll groove binds LPS and passes it from LptB2FG to LptA; this is the defining activity of the single-subfamily family and the core MF of both reviewed members.
lpta_bridge LptA family
PANTHER:PTHR36504
Family 		lipopolysaccharide transfer activity
GO:0140332 		Family Supported
Family review supports GO:0140332 FAMILY_WIDE. LptA oligomers carry LPS through their hydrophobic groove from LptC to LptD; this is the defining activity of the single-subfamily family.
lpte_plug LptE family
PANTHER:PTHR38098
Family 		lipopolysaccharide binding
GO:0001530 		Family Supported
Family review supports GO:0001530 FAMILY_WIDE. LPS binding is shown directly for E. coli LptE and underlies its role in disaggregating LPS at the translocon. PAINT places the term at the gammaproteobacterial node; the family is a single subfamily of LptD plug lipoproteins and no member is known to lack the activity, so the scope is not narrowed.

Gene-review completeness (14/14 grounded genes reviewed)

14 complete review(s) · 0 with deep research · 0 missing review · 14 reviewed but lacking deep research

Gene Review Complete Deep research
lptA P0ADV1 ✓ ✓ ✗
lptA Q88P98 ✓ ✓ ✗
lptB P0A9V1 ✓ ✓ ✗
lptB Q88P99 ✓ ✓ ✗
lptC P0ADV9 ✓ ✓ ✗
lptC Q88P97 ✓ ✓ ✗
lptD A0A140FVZ0 ✓ ✓ ✗
lptD P31554 ✓ ✓ ✗
lptE P0ADC1 ✓ ✓ ✗
lptE Q88DN0 ✓ ✓ ✗
lptF P0AF98 ✓ ✓ ✗
lptG P0ADC6 ✓ ✓ ✗
PP_0982 Q88P71 ✓ ✓ ✗
PP_0983 Q88P70 ✓ ✓ ✗

Details

Context
bacteriaNCBITaxon:2
LPS transport from inner to outer membraneBiological Processbacterial_lps_transport
lipopolysaccharide transportGO:0015920 lipopolysaccharide transport systemGO:0062051
Context
bacteriaNCBITaxon:2

Connections

Part 1: ATP-driven LPS extraction from the inner membrane
LptB2FGC inner-membrane extraction machineProtein Complexinner_membrane_lptb2fgc

Cytoplasmic LptB ATPases energize the LptF/LptG transmembrane subunits, which take up LPS from the inner membrane into their central cavity and push it out into the periplasm. LptC couples the inner-membrane machine to the periplasmic transport bridge.

Annotons

LptB2FG LPS extraction transporter
lptb2fg_extractor
Participant: Protein Complex: LptB2FG ABC transporter
Protein Complex:
LptB2FG ABC transporterGO:0043190
Active units:
LptB ATPase (two copies)
Participant: Family: LptB family
Family:
LptB familyPANTHER:PTHR45772:SF10
Representative Members: lptB (Escherichia coli K-12)UniProtKB:P0A9V1 lptB (Pseudomonas putida KT2440)UniProtKB:Q88P99
Role: Cytoplasmic nucleotide-binding domains whose ATP hydrolysis drives the transporter.
Function:
ATP hydrolysis activityGO:0016887
LptF permease subunit
Participant: Family: LptF permease subfamily
Family:
LptF permease subfamilyPANTHER:PTHR33529:SF7
Representative Members: lptF (Escherichia coli K-12)UniProtKB:P0AF98 PP_0982 / lptF (Pseudomonas putida KT2440)UniProtKB:Q88P71
Role: One half of the transmembrane cavity; its periplasmic beta-jellyroll docks LptC.
LptG permease subunit
Participant: Family: LptG permease subfamily
Family:
LptG permease subfamilyPANTHER:PTHR33529:SF2
Representative Members: lptG (Escherichia coli K-12)UniProtKB:P0ADC6 PP_0983 / lptG (Pseudomonas putida KT2440)UniProtKB:Q88P70
Role: Other half of the transmembrane cavity; binds the lipid A phosphates.

Function

lipopolysaccharide transfer activityGO:0140332 Activity of the LptB2FG complex, not of any single subunit: it removes LPS from the outer leaflet of the inner membrane and pushes it into the LptC/LptA/LptD groove, the donor-membrane part of the transfer completed by the rest of the Lpt machine. The subunit gene reviews record it with the contributes_to qualifier; LptB additionally enables ATP hydrolysis.

Locations

plasma membraneGO:0005886

Extracts LPS from the inner membrane and advances it into the periplasmic bridge, powered by ATP hydrolysis in LptB.

LptC bridge anchor
lptc_bridge_anchor
Participant: Family: LptC family
Family:
LptC familyPANTHER:PTHR37481
Representative Members: lptC (Escherichia coli K-12)UniProtKB:P0ADV9 lptC (Pseudomonas putida KT2440)UniProtKB:Q88P97

Function

lipopolysaccharide transfer activityGO:0140332

Locations

plasma membraneGO:0005886

Receives extracted LPS and connects LptFG to LptA.

Part 2: periplasmic transfer across the Lpt bridge
LptA periplasmic bridgeTransport Stepperiplasmic_lpta_bridge

LptA proteins form a hydrophobic groove that extends the LptC/LptD beta-jellyroll bridge across the periplasm.

Annotons

LptA bridge protein
lpta_bridge
Participant: Family: LptA family
Family:
LptA familyPANTHER:PTHR36504
Representative Members: lptA (Escherichia coli K-12)UniProtKB:P0ADV1 lptA (Pseudomonas putida KT2440)UniProtKB:Q88P98

Function

lipopolysaccharide transfer activityGO:0140332

Locations

outer membrane-bounded periplasmic spaceGO:0030288

Transfers LPS through the periplasmic bridge.

Part 3: LPS insertion into the outer membrane
LptD/LptE outer-membrane transloconProtein Complexouter_membrane_lptde

LptD forms the outer-membrane beta-barrel and lateral exit, while the LptE lipoprotein forms the lumenal plug, binds LPS, and supports translocon assembly.

Annotons

LptD/LptE outer-membrane translocon
lptde_translocon
Participant: Protein Complex: LptD/LptE translocon
Protein Complex:
LptD/LptE transloconGO:1990351
Active units:
LptD beta-barrel
Participant: Family: LptD family
Family:
LptD familyPANTHER:PTHR30189:SF1
Representative Members: lptD (Escherichia coli K-12)UniProtKB:P31554 lptD (Pseudomonas putida KT2440)UniProtKB:A0A140FVZ0
Role: 26-strand barrel with a lateral gate; its N-terminal beta-jellyroll receives LPS from LptA.
LptE plug lipoprotein
Participant: Family: LptE family
Family:
LptE familyPANTHER:PTHR38098
Representative Members: lptE (Escherichia coli K-12)UniProtKB:P0ADC1 lptE (Pseudomonas putida KT2440)UniProtKB:Q88DN0
Role: Plugs the LptD barrel, binds LPS, and is required for LptD assembly.
Function:
lipopolysaccharide bindingGO:0001530

Function

lipopolysaccharide transmembrane transporter activityGO:0015221 Activity of the LptD/LptE pair: LPS arriving through the periplasmic bridge passes through the translocon into the outer leaflet of the outer membrane. The LptD and LptE gene reviews record it with the contributes_to qualifier; LptE additionally enables LPS binding.

Locations

cell outer membraneGO:0009279

Accepts LPS from the bridge and inserts it laterally into the outer leaflet of the outer membrane.