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Enzyme Nomenclature
Information on EC 7.5.2.5 - ABC-type lipopolysaccharide transporter and Organism(s) Escherichia coli and UniProt Accession P0A9V1
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7.5.2.5 ABC-type lipopolysaccharide transporterIUBMB Comments
An ATP-binding cassette (ABC) type transporter, characterized by the presence of two similar ATP-binding domains/proteins and two integral membrane domains/proteins. Does not undergo phosphorylation during the transport process. The enzyme, characterized from the bacterium Escherichia coli, functions as part of the lipopolysaccharide (LPS) export system, a seven protein system that translocates LPS from the inner- to the outer membrane. The ATPase activity in this system is implicated in releasing LPS from the inner membrane.
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The taxonomic range for the selected organisms is: Escherichia coli
The enzyme appears in selected viruses and cellular organisms
The enzyme appears in selected viruses and cellular organisms
topSYNONYM 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
lipopolysaccharide-transporting ATPase
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
ATP + H2O + lipopolysaccharide[side 1] = ADP + phosphate + lipopolysaccharide[side 2]
LptB2FG tetramer mechanism: 1. Resting: the LptB nucleotide-binding sites are unoccupied, and the LptF/G cavity is oriented inwards. 2. Open: ATP binds LptB, inducing the LptF/G cavity to open away from the IM, and receives the Lipid A moiety of LPS, which is still embedded in the IM. 3. Close: LptB hydrolyzes ATP, inducing the LptF/G cavity to close again. LPS is forced out of the IM into the periplasm
REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
hydrolysis of phosphoric ester
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transmembrane transport
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SYSTEMATIC NAME
IUBMB Comments
ATP phosphohydrolase (ABC-type, lipopolysaccharide-exporting)
An ATP-binding cassette (ABC) type transporter, characterized by the presence of two similar ATP-binding domains/proteins and two integral membrane domains/proteins. Does not undergo phosphorylation during the transport process. The enzyme, characterized from the bacterium Escherichia coli, functions as part of the lipopolysaccharide (LPS) export system, a seven protein system that translocates LPS from the inner- to the outer membrane. The ATPase activity in this system is implicated in releasing LPS from the inner membrane.
CAS REGISTRY NUMBER
COMMENTARY
9000-83-3
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SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
ATP + H2O + lipopolysaccharide[side 1]
ADP + phosphate + lipopolysaccharide[side 2]
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?
ATP + H2O + Lipid A/in
ADP + phosphate + Lipid A/out
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translocation of the lipid A core moiety across the inner membrane requires the ABC transporter MsbA,which mediates the flipping from the inner leaflet to the outer leaflet of the inner membrane, lipopolysaccharide translocation mechanism and system, structure modelling, overview
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?
additional information
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the Lpt (LPS transport) system forms a continuous protein bridge across the inner membrane, periplasm and outer membrane. LptB, LptG, and LptF extract LPS (lipopolysaccharide) from the inner leaflet of the IM (inner membrane) through an ATPase-dependent mechanism
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?
additional information
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ATPase assays are conducted for both LptB and LptB2FGC variants
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NATURAL SUBSTRATE
NATURAL PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
ATP + H2O + lipopolysaccharide[side 1]
ADP + phosphate + lipopolysaccharide[side 2]
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?
ATP + H2O + Lipid A/in
ADP + phosphate + Lipid A/out
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translocation of the lipid A core moiety across the inner membrane requires the ABC transporter MsbA,which mediates the flipping from the inner leaflet to the outer leaflet of the inner membrane, lipopolysaccharide translocation mechanism and system, structure modelling, overview
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?
additional information
?
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the Lpt (LPS transport) system forms a continuous protein bridge across the inner membrane, periplasm and outer membrane. LptB, LptG, and LptF extract LPS (lipopolysaccharide) from the inner leaflet of the IM (inner membrane) through an ATPase-dependent mechanism
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
ATP
ATP hydrolysis induces conformational changes, the switch region moves and the side chain of H195 flips, ATP binding structure, overview. The H195 is imidazole side chain directly interacts with the gamma-phosphate of ATP. Through a bridging water molecule, the glutamate E163 contacts the beta-phosphate of the nucleotide
METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
additional information
the LptB2FG complex interacts with the other IM-bound subunit, LptC, and influences LPS extraction. LptC reduces the ATPase of the activity of the complex in vitro
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ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
novobiocin
LptB2FG activity and subsequent LPS transport are further enhanced in the presence of the antibiotic novobiocin, a hydrophobic DNA gyrase inhibitor. Novobiocin binds to the Q-loop and directly interacts with F90 and R91, strongly indicating that LptF/G's effect on LptB ATPase activity is mediated directly through their coupling interaction
additional information
ATPase activity is substantially higher with the full complex
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ORGANISM
COMMENTARY
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY
GeneOntology No.
LITERATURE
SOURCE
as LptB2FGC enzyme complex, residue F90 is essential for proper formation of the Lpt inner membrane complex, transmembrane complex. The groove region of LptB is essential for interaction with inner membrane partners
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GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
evolution
LptB2FG represents a third distinct type of ABC transporter, deemed type-III
malfunction
physiological function
additional information
malfunction
mutations in the nucleotide-binding domain, LptB, of the transporter inactivates transporter function in vivo
malfunction
the C-term LptC mutation reduces the stability of the overall LptB2FGC complex, so increased LptB expression compensates by shifting the binding equilibrium in favor of the LptB2FG complex
physiological function
Gram-negative bacteria have a dense outer membrane (OM) coating of lipopolysaccharides, which is essential to their survival. This coating is assembled by the LPS (lipopolysaccharide) transport (Lpt) system, a coordinated seven-subunit protein complex that spans the cellular envelope. LPS transport is driven by an ATPase-dependent mechanism dubbed the protein-bridge PEZ model, whereby a continuous stream of LPS molecules is pushed from subunit to subunit. The Lpt subunits form a continuous complex from the inner membrane (IM) to the OM and LPS is propelled along it continuously by the ATPase activity of LptB. Subunit-scale mechanisms of LPS transport include the novel ABC-like mechanism of the LptB2FG subcomplex and the lateral insertion of LPS into the OM by LptD/E, overview. The tightly regulated interactions between these connected subcomplexes suggest a pathway that can react dynamically to membrane stress and may prove to be a valuable target for new antibiotic therapies for Gram-negative pathogens. LPS is synthesized at the cytoplasmic side of the IM before it is transported to the OM. The LptB2FG tetramer extracts LPS from the outer leaflet of the IM and provides the energy to drive LPS transport through an ATPase-dependent mechanism, the LptB2FG complex drives LPS extraction from the IM to the periplasm
physiological function
the enzme is an LPS transporters. LPS transporters are ABC exporters that are known to export extremely hydrophobic compounds, such as lipids, drugs, and steroids. LptB is implicated in lipopolysaccharide transport to the outer membrane of Escherichia coli
additional information
identification of the specific subunit-to-subunit interactions that make the continuous transport of LPS from the cytoplasm to the exterior of the outer membrane by Lpt systems possible. The Lpt system is an oligomeric complex consisting of Lpt proteins A through G. The membrane-bound LptB, F, G and C subunits are connected to the LptD/E heterodimer in the OM by periplasmic LptA. LptB's catalytic activity couples to the LptF/G heterodimer's extraction of LPS like other ABC transporters, wherein the coupling helices of the TMD interact with the variable Q-loop of the NBD. Structural comparison of ATP-and ADP-bound LptB shows that ATP binding, hydrolysis and release induce conformational changes in the Q-loop region, mediated predominantly by two conserved residues (F90 and R91). LptC may be important to the efficient and stable assembly of the LptB2FG complex, in addition to directly transporting LPS
additional information
residue F90 is essential for proper formation of the Lpt inner membrane complex. crystal structures of LptB pre- and post-ATP hydrolysis suggest a role for an active site residue in phosphate exit. Residues E163, H195, and F90 of LptB are required for cell viability. E163 is essential for catalysis, through a bridging water molecule, this glutamate contacts the beta-phosphate of the nucleotide. ATP hydrolysis induces conformational changes. Conformational changes upon ATP hydrolysis show how reorganization of the active site causes changes in the region of LptB believed to interact with LptF/G. The dramatic movement of the switch region observed during ATP hydrolysis plays a critical role in communicating changes in the active site to changes in the transmembrane domains. The groove region of LptB is essential for interaction with inner membrane partners
SUBUNIT
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
additional information
LptB possesses an overall fold resembling that of nucleoside triphosphate-binding (NBD) structures. It contains the canonical L-shaped architecture composed of a RecA-like alpha/beta-ATPase domain and a structurally diverse alpha-helical domain. The RecA-like domain contains the Walker A and Walker B motifs present in many NBD proteins. This domain also furnishes Mg2+- and nucleotide-binding motifs specific to ABC proteins, namely, the Q-loop, which links the more highly conserved alpha/beta-ATPase domain to the alpha-helical domain, and the switch region, which contains the conserved H195
CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
crystal structures of recombinant His-tagged LptB pre- and post-ATP hydrolysis, for native enzyme: mixing of 0.001 ml of 7-10 mg/mL protein in 10% v/v glycerol, 2.5 mM ATP, 2.5 mM MgCl2, 150 mM NaCl, and 20 mM Tris, pH 8.0, with 0.001 ml of reservoir solution containing 0.1 M MES, pH 6.5, and 30% w/v PEG 4000, and for SeMet-LptB-His enzyme: mixing of 0.002 ml of 7-10 mg/mL protein in 10% v/v glycerol, 2.5 mM ATP, 2.5 mM MgCl2, 150 mM NaCl, and 20 mM Tris, pH 8.0, with 0.001 ml of reservoir solution composed of 0.1 M MES, pH 6.5, and 31% w/v PEG 4000, room temperature, several days, X-ray diffraction structure determination and analysis, molecular replacement using the native LptB-Mg2+-ADP structure as the search model
PROTEIN VARIANTS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
E163Q
site-directed mutagenesis, catalytically inactive variant, introduction of plasmid-encoded LptBE163Q-His8 variant into the wild-type strain results in increased outer membrane permeability, dominant-negative phenotype
F90A
site-directed mutagenesis, catalytically inactive variant, the F90A variant cannot form a stable complex with the Lpt-inner membrane components
F90Y
site-directed mutagenesis, the LptB and LptB-His8 F90Y variants are functional in vivo
H195A
site-directed mutagenesis, catalytically inactive variant, introduction of plasmid-encoded LptB-H195A-His8 variant into the wild-type strain results in increased outer membrane permeability, dominant-negative phenotype
additional information
additional information
amorphadiene, the precursor of antimalarial drug artemisinin from Artemisia annua, is secreted from Escherichia coli cells overexpressing the biosynthetic pathway. The overexpression of transporters in the lipopolysaccharide transport system (msbA, lptD, lptCABFG) improves amorphadiene (AD) production. AD production in both early stage (8 h) and final stage (24 h) is increased by more than twofold in the strains that overexpress lptCABFG or msbA. But co-overexpression of LptCABFG and LptD or LptD and TolC does not enhance AD-specific production synergistically, despite the fact that the AD titer is increased mainly due to the increased cell density, overview
additional information
construction of chromosomal deletion of lptB and replacement with a kanamycin-resistance cassette (DELTAlptB:: kan allele), where the region from the second codon to the stop codon of lptB is deleted
PURIFICATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
active recombinant His8-tagged wild-type and mutant LptB enzymes and His6-tagged LptB-LptFG from Escherichia coli strains for activity assays and crystallization are purified by ultracentrifugation, nickel affinity chromatography, ultrafiltration, and gel filtration, recombinant His6/8-tagged enzyme for immunoblotting is purified from Escherichia coli by ultracentrifugation, nickel affinity chromatography, trichloroacetate precipitation and acetone wash, boiling, and SDS-PAGE
CLONED (Commentary)
ORGANISM
UNIPROT
LITERATURE
gene lptB, recombinant expression of His8-tagged wild-type and mutant LptB enzymes and of His6-tagged LptB-LptFG in Escherichia coli strain DH5alpha and in Escherichia coli KRX cells from different plasmid constructions, recombinant expression of selenomethionine-labeled enzyme from Escherichia coli strain BL21(DE3)
gene lptB, the gene belongs to the lipopolysaccharide transport system encoded by operon lptCABFG, overexpression of the lptCABFG operon in Escherichia coli strain K12 MG1655 DELTArecADELTAendA DE3, co-overexpression of LptCABFG and LptD or LptD and TolC, all genes and operons are inserted into modified RK2 (amp) plasmid with the Pm promoter replaced with TM1 promoter, quantitative real-time PCR expression analysis
EXPRESSION
ORGANISM
UNIPROT
LITERATURE
the C-term LptC mutation reduces the stability of the overall LptB2FGC complex, so increased LptB expression compensates by shifting the binding equilibrium in favor of the LptB2FG complex
REF.
AUTHORS
TITLE
JOURNAL
VOL.
PAGES
YEAR
ORGANISM (UNIPROT)
PUBMED ID
SOURCE
Suits, M.D.; Sperandeo, P.; Deho, G.; Polissi, A.; Jia, Z.
Novel structure of the conserved gram-negative lipopolysaccharide transport protein A and mutagenesis analysis
J. Mol. Biol.
380
476-488
2008
Escherichia coli
Zhang, C.; Chen, X.; Stephanopoulos, G.; Too, H.P.
Efflux transporter engineering markedly improves amorphadiene production in Escherichia coli
Biotechnol. Bioeng.
113
1755-1763
2016
Escherichia coli (P0A9V1)
Hicks, G.; Jia, Z.
Structural basis for the lipopolysaccharide export activity of the bacterial lipopolysaccharide transport system
Int. J. Mol. Sci.
19
E2680
2018
Escherichia coli (P0A9V1), Neisseria meningitidis serogroup B / serotype 15 (E6MYT4), Neisseria meningitidis serogroup B / serotype 15 H44/76 (E6MYT4), Pseudomonas aeruginosa (A0A071L2Z5)
EXTERNAL LINKS (specific for EC-Number 7.5.2.5)
Transporter Classification Database (TCDB): 3.A.1.106.15
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