|Gene:||lptC||Accession Numbers: G7664 (EcoCyc), b3199, ECK3188|
Component of: lipopolysaccharide transport system (extended summary available)
LptC is a component of the Lpt lipopolysaccharide (LPS) transport system in E. coli K-12.
lptC is essential for growth in E. coli [Baba06, Sperandeo06]. Depletion of lptC leads to growth arrest and irreversible cell damage. Sensitivity to SDS and bile salts indicates a defective outer membrane [Sperandeo06]. LptC contains a single N-terminal membrane spanning domain and a large soluble periplasmic domain [Sperandeo07, Tran10]. LptC forms a complex with LptF, LptG and LptB [Narita09]. LptC binds rough and smooth LPS in vitro [Tran10]. LptA can displace LPS from the purified periplasmic domain of LptC in vitro but not vice versa [Tran10].
Gene Citations: [Martorana11]
Locations: periplasmic space, inner membrane
|Map Position: [3,340,858 -> 3,341,433] (72.01 centisomes)||Length: 576 bp / 191 aa|
Molecular Weight of Polypeptide: 21.703 kD (from nucleotide sequence)
Unification Links: ASAP:ABE-0010508 , EchoBASE:EB2657 , EcoGene:EG12806 , EcoliWiki:b3199 , Mint:MINT-7137017 , OU-Microarray:b3199 , PortEco:lptC , PR:PRO_000023115 , Protein Model Portal:P0ADV9 , RefSeq:NP_417666 , RegulonDB:G7664 , SMR:P0ADV9 , String:511145.b3199 , UniProt:P0ADV9
|Biological Process:||GO:0015920 - lipopolysaccharide transport
GO:0046836 - glycolipid transport [Sperandeo06]
|Molecular Function:||GO:0005515 - protein binding
GO:0017089 - glycolipid transporter activity [Sperandeo06]
GO:0042802 - identical protein binding [Sperandeo11]
GO:0015221 - lipopolysaccharide transmembrane transporter activity [GOA01a]
|Cellular Component:||GO:0005886 - plasma membrane
[UniProtGOA11, UniProtGOA11a, Zhang07]
GO:0005887 - integral component of plasma membrane [Tran10]
GO:0016021 - integral component of membrane [UniProtGOA11a, Sperandeo08]
GO:0030288 - outer membrane-bounded periplasmic space [Tran10]
GO:0016020 - membrane [UniProtGOA11a, GOA01a]
|MultiFun Terms:||cell structure → membrane|
|transport → Channel-type Transporters → Pyrophosphate Bond (ATP; GTP; P2) Hydrolysis-driven Active Transporters → The ATP-binding Cassette (ABC) Superfamily + ABC-type Uptake Permeases → ABC superfamily, membrane component|
|Growth Medium||Growth?||T (°C)||O2||pH||Osm/L||Growth Observations|
|LB Lennox||No||37||Aerobic||7||No [Baba06, Comment 1]|
Subunit of: lipopolysaccharide transport system
Subunit composition of
lipopolysaccharide transport system = [(LptD)(LptE)][(LptG)(LptB)2(LptF)][LptC][LptA]
outer membrane lipopolysaccharide transport and assembly complex = (LptD)(LptE) (extended summary available)
outer membrane lipopolysaccharide transport and assembly complex - LptD subunit = LptD (extended summary available)
outer membrane lipopolysaccharide transport and assembly complex - LptE subunit = LptE (extended summary available)
LptBFG ABC transporter = (LptG)(LptB)2(LptF)
In E. coli K-12 the system responsible for transporting lipolysaccharide (LPS) from the inner membrane to the outer membrane consists of seven Lpt proteins - LptB, LptF, LptG, LptC, LptA, LptD and LptE. Together these proteins form a transenvelope bridge that transports LPS from the inner membrane, across the periplasm to the outer leaflet of the outer membrane. LptCBFG is an ATP Binding Cassette (ABC) transporter which facilitates the release of LPS from the inner membrane. LptA is a periplasmic protein initially thought to be an LPS chaperone but now believed to act as a bridge between the inner membrane and the outer membrane. LptDE is the outer membrane complex that functions to assemble LPS at the cell surface.The Lpt system acts downstream from an LPS flippase, MsbA, which is responsible for flipping the lipid A-core structure across the inner membrane.
LptF and LptG are inner membrane proteins [Chng10] each with six predicted transmembrane segments and a C-terminus located in the cytoplasm [Daley05]. lptF and lptG are essential in E.coli [Ruiz08b]. Depletion of LptF and/or LptG results in increased outer membrane permeability and lipopolysaccharides do not reach the outer leaflet of the outer membrane [Ruiz08b]. LptB contains an ATP-binding domain [Sperandeo07] and purifies as part of a 140 kD inner membrane complex [Stenberg05]. LptC contains a predicted N-terminal membrane spanning domain and a large soluble domain oriented towards the periplasm [Sperandeo07, Tran10]. LptC binds smooth and rough LPS in vitro [Tran10]. LptC forms a complex with LptF, LptG and LptB [Narita09]. Purified LptC is a dimer in vitro [Sperandeo11].
LptA is a periplasmic protein [Sperandeo07]. LptA and LptC interact in vivo and form a stable complex [Sperandeo11].The N-terminal region of LptA interacts with the C-terminal region of LptC, and the C-terminal region of LptA interacts with the N-terminal region of LptD in vivo [Freinkman12]. It is not clear if both these interactions occur simultaneously. LptA can form head-to-toe homodimers in vivo [Freinkman12]. LptA cannot interact with variants of LptD that lack functional disulfide bonds [Freinkman12].
All 7 Lpt proteins fractionate in the so-called OM(L)) fraction, which contains both inner membranes and outer membranes [Chng10]. LptC co-purifies with LptB, LptF and LptG; additionally any of the these four components is able to pull-down LptA, LptD and LptE [Chng10]. LPS transport can be reconstituted in vitro. LPS binds inside the β jellyroll structure of the LptC and LptA proteins [Okuda12]. Interaction of LPS with LptC and LptA depends on the IM complex LptBFG and requires ATP [Okuda12]. LPS does not interact with LptA in the absence of LptC [Okuda12]. LPS transport includes two energy dependent steps: extraction of LPS from the inner membrane to the periplasmic domain of membrane bound LptC; and transfer of LPS from LptC to LptA [Okuda12].
The genes lptB and lptA are located in a single operon. Random and directed transposition mutagenesis showed lptA and lptB are essential genes [Gerdes03, Serina04, Sperandeo06, Baba06]. lptC is also essential for growth in E. coli [Baba06, Sperandeo06]. Depletion of lptC leads to growth arrest and irreversible cell damage. Sensitivity to SDS and bile salts indicates a defective outer membrane [Sperandeo06]. Depleting any of LptA, LptB, LptC, LptD or LptE results in a similar phenotype: these cells have abnormal membrane structures in the periplasm and they do not transport de novo synthesized LPS to the outer membrane. These strains accumulate an anomolous form of LPS that fractionates in a different manner to native LPS. They also accumulate a higher molecular weight, modifed form of LPS ligated to colonic acid. Disruption of O-antigen ligase abolishes formation of this HMW modified LPS [Sperandeo08].
lptAB can be expressed from a σE-dependent promoter [Sperandeo07]. Membrane fractionation experiments show that blocking expression of lptA or lptB prevents LPS from being transported to the outer membrane [Sperandeo07].
|Biological Process:||GO:0015920 - lipopolysaccharide transport [Sperandeo08]|
|Molecular Function:||GO:0015437 - lipopolysaccharide-transporting ATPase activity [Okuda12]|
|Cellular Component:||GO:0030313 - cell envelope [Chng10]|
Enzymatic reaction of: transport of lipopolysaccharide (lipopolysaccharide transport system)
This reaction represents the movement of lipopolysaccharide from the inner membrane, across the periplasm to the outer leaflet of the outer membrane,
|Transmembrane-Region||7 -> 25|
Peter D. Karp on Thu Jan 16, 2003:
Predicted gene function revised as a result of E. coli genome reannotation by Serres et al. [Serres01 ].
Markus Krummenacker on Tue Oct 14, 1997:
Gene object created from Blattner lab Genbank (v. M52) entry.
Baba06: Baba T, Ara T, Hasegawa M, Takai Y, Okumura Y, Baba M, Datsenko KA, Tomita M, Wanner BL, Mori H (2006). "Construction of Escherichia coli K-12 in-frame, single-gene knockout mutants: the Keio collection." Mol Syst Biol 2;2006.0008. PMID: 16738554
Gerdes03: Gerdes SY, Scholle MD, Campbell JW, Balazsi G, Ravasz E, Daugherty MD, Somera AL, Kyrpides NC, Anderson I, Gelfand MS, Bhattacharya A, Kapatral V, D'Souza M, Baev MV, Grechkin Y, Mseeh F, Fonstein MY, Overbeek R, Barabasi AL, Oltvai ZN, Osterman AL (2003). "Experimental determination and system level analysis of essential genes in Escherichia coli MG1655." J Bacteriol 185(19);5673-84. PMID: 13129938
Martorana11: Martorana AM, Sperandeo P, Polissi A, Deho G (2011). "Complex transcriptional organization regulates an Escherichia coli locus implicated in lipopolysaccharide biogenesis." Res Microbiol 162(5);470-82. PMID: 21402154
Narita09: Narita S, Tokuda H (2009). "Biochemical characterization of an ABC transporter LptBFGC complex required for the outer membrane sorting of lipopolysaccharides." FEBS Lett 583(13);2160-4. PMID: 19500581
Polissi14: Polissi A, Sperandeo P (2014). "The lipopolysaccharide export pathway in Escherichia coli: structure, organization and regulated assembly of the Lpt machinery." Mar Drugs 12(2);1023-42. PMID: 24549203
Ruiz08b: Ruiz N, Gronenberg LS, Kahne D, Silhavy TJ (2008). "Identification of two inner-membrane proteins required for the transport of lipopolysaccharide to the outer membrane of Escherichia coli." Proc Natl Acad Sci U S A 105(14);5537-42. PMID: 18375759
Serina04: Serina S, Nozza F, Nicastro G, Faggioni F, Mottl H, Deho G, Polissi A (2004). "Scanning the Escherichia coli chromosome by random transposon mutagenesis and multiple phenotypic screening." Res Microbiol 155(8);692-701. PMID: 15380559
Sperandeo06: Sperandeo P, Pozzi C, Deho G, Polissi A (2006). "Non-essential KDO biosynthesis and new essential cell envelope biogenesis genes in the Escherichia coli yrbG-yhbG locus." Res Microbiol 157(6);547-58. PMID: 16765569
Sperandeo07: Sperandeo P, Cescutti R, Villa R, Di Benedetto C, Candia D, Deho G, Polissi A (2007). "Characterization of lptA and lptB, two essential genes implicated in lipopolysaccharide transport to the outer membrane of Escherichia coli." J Bacteriol 189(1);244-53. PMID: 17056748
Sperandeo08: Sperandeo P, Lau FK, Carpentieri A, De Castro C, Molinaro A, Deho G, Silhavy TJ, Polissi A (2008). "Functional analysis of the protein machinery required for transport of lipopolysaccharide to the outer membrane of Escherichia coli." J Bacteriol 190(13);4460-9. PMID: 18424520
Sperandeo11: Sperandeo P, Villa R, Martorana AM, Samalikova M, Grandori R, Deho G, Polissi A (2011). "New insights into the Lpt machinery for lipopolysaccharide transport to the cell surface: LptA-LptC interaction and LptA stability as sensors of a properly assembled transenvelope complex." J Bacteriol 193(5);1042-53. PMID: 21169485
Stenberg05: Stenberg F, Chovanec P, Maslen SL, Robinson CV, Ilag LL, von Heijne G, Daley DO (2005). "Protein complexes of the Escherichia coli cell envelope." J Biol Chem 280(41);34409-19. PMID: 16079137
Tran10: Tran AX, Dong C, Whitfield C (2010). "Structure and functional analysis of LptC, a conserved membrane protein involved in the lipopolysaccharide export pathway in Escherichia coli." J Biol Chem 285(43);33529-39. PMID: 20720015
Villa13: Villa R, Martorana AM, Okuda S, Gourlay LJ, Nardini M, Sperandeo P, Deho G, Bolognesi M, Kahne D, Polissi A (2013). "The Escherichia coli Lpt transenvelope protein complex for lipopolysaccharide export is assembled via conserved structurally homologous domains." J Bacteriol 195(5);1100-8. PMID: 23292770
Zhang07: Zhang N, Chen R, Young N, Wishart D, Winter P, Weiner JH, Li L (2007). "Comparison of SDS- and methanol-assisted protein solubilization and digestion methods for Escherichia coli membrane proteome analysis by 2-D LC-MS/MS." Proteomics 7(4);484-93. PMID: 17309111
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