Protease homolog BepA (YfgC) promotes assembly and degradation of β-barrel membrane proteins in
            <i>Escherichia coli</i>

Narita, Shin‐ichiro; Masui, Chigusa; Suzuki, Takehiro; Dohmae, Naoshi; Akiyama, Yoshinori

doi:10.1073/pnas.1312012110

Cited by 67 publications

(153 citation statements)

References 52 publications

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“…Most of the sensitive mutants corresponded to genes already known to be involved in envelope assembly, such as mutants defective in LPS biosynthesis (rfaC, rfaD, rfaE, rfaF, rfaH, rfaI, and rfaP mutants) or in ␤-barrel insertion at the OM (surA, bamB, and bamE mutants), which validated our experimental approach (20,21). Four mutants lacked proteins of unknown function (yciM, yfgC, yraP, and ybiX mutants) although recently YfgC has been implicated in the degradation of misfolded ␤-barrel proteins at the OM (22). We tested the sensitivity of these four mutants to other hydrophobic antibiotics and found that strains lacking yciM were the most sensitive (see Table S4), which prompted us to investigate the properties of the yciM mutant and to characterize the corresponding protein.…”

Section: Resultssupporting

confidence: 61%

Insights into the Function of YciM, a Heat Shock Membrane Protein Required To Maintain Envelope Integrity in Escherichia coli

Nicolaes¹,

Hajjaji²,

Davis³

et al. 2013

Journal of Bacteriology

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The cell envelope of Gram-negative bacteria is an essential organelle that is important for cell shape and protection from toxic compounds. Proteins involved in envelope biogenesis are therefore attractive targets for the design of new antibacterial agents. In a search for new envelope assembly factors, we screened a collection of Escherichia coli deletion mutants for sensitivity to detergents and hydrophobic antibiotics, a phenotype indicative of defects in the cell envelope. Strains lacking yciM were among the most sensitive strains of the mutant collection. Further characterization of yciM mutants revealed that they display a thermosensitive growth defect on low-osmolarity medium and that they have a significantly altered cell morphology. At elevated temperatures, yciM mutants form bulges containing cytoplasmic material and subsequently lyse. We also discovered that yciM genetically interacts with envC, a gene encoding a regulator of the activity of peptidoglycan amidases. Altogether, these results indicate that YciM is required for envelope integrity. Biochemical characterization of the protein showed that YciM is anchored to the inner membrane via its N terminus, the rest of the protein being exposed to the cytoplasm. Two CXXC motifs are present at the C terminus of YciM and serve to coordinate a redox-sensitive iron center of the rubredoxin type. Both the N-terminal membrane anchor and the C-terminal iron center of YciM are important for function.A ntibiotic resistance has become a worldwide problem that threatens the effectiveness of many medicines used today to treat bacterial infections. A particularly serious threat is the emergence of Gram-negative pathogens, including Escherichia coli and Pseudomonas aeruginosa, which are resistant to all of the available antibacterial agents (1). It is therefore urgent to develop new antibiotics active against Gram-negative bacteria, which requires a deep understanding of the biology of these organisms. Proteins playing a role in the assembly of the cell envelope are attractive targets for antibiotic development because this structure is essential for viability and protection against toxic compounds such as antibiotics.The envelope of Gram-negative bacteria is characterized by the presence of two concentric membranes, the inner membrane (IM) and outer membrane (OM), which are separated by the periplasm, a compartment that represents between 10 and 20% of the total cell volume and contains the peptidoglycan layer, or sacculus (2-4). The peptidoglycan sacculus is a heteropolymeric macromolecule composed of relatively short glycan strands and peptide cross-links, which serve to maintain cell morphology and give protection from turgor pressure. Although several proteins that play a key role in the biogenesis of the cell envelope have been identified recently (5-7), we have a poor understanding of how this complex architecture is assembled and of how envelope biogenesis is coordinated with cell growth and division. For instance, we do not know how the phospholipids that ...

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Section: Resultssupporting

confidence: 61%

Insights into the Function of YciM, a Heat Shock Membrane Protein Required To Maintain Envelope Integrity in Escherichia coli

Nicolaes¹,

Hajjaji²,

Davis³

et al. 2013

Journal of Bacteriology

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“…For example, the metalloprotease BepA and the disulfide isomerase DsbC have also been implicated in LptD biogenesis and disulfide rearrangement 86, 87 . BepA degrades misfolded LptD and its proposed chaperone function stimulates disulfide rearrangement in LptD through an unknown mechanism 87 . Overexpression of a variant of DsbC that traps substrates has shown that this variant interacts with LptD 86 .…”

Section: Regulation Of Lpt Bridge Formationmentioning

confidence: 99%

“…However, the biological significance of the DsbC-LptD interaction is unclear because deletion of dsbC has no detectable effect on the formation of properly oxidized LptD. Furthermore, disulfide-bond rearrangement intermediates of LptD have been shown to interact with DsbA, instead of DsbC 82, 83, 87 .…”

Section: Regulation Of Lpt Bridge Formationmentioning

confidence: 99%

Lipopolysaccharide transport and assembly at the outer membrane: the PEZ model

et al. 2016

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Gram-negative bacteria contain a double-membrane cellular envelope that enables them to colonize harsh environments and prevents entry of many clinically available antibiotics. A main component of most outer membranes is lipopolysaccharide (LPS), a glycolipid containing multiple fatty acyl chains and up to hundreds of sugars that is synthesized in the cytoplasm. In the last two decades, the proteins responsible for transporting LPS across the cellular envelope and assembling it at the cell surface in Escherichia coli have been identified, but it remains unclear how they function. In this Review, we discuss recent advances in this area and present a model explaining how energy from the cytoplasm is used to power LPS transport across the cellular envelope to the cell surface.

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“…Proper interaction of LptC with LptB 2 FG is necessary for LptA recruitment (22). Interaction of the N-terminal domain of LptD with LptA requires the correct maturation of the LptDE complex that in turns depends on nonconsecutive disulfide bond formation in LptD (16); LptE and the chaperone/protease BepA have been implicated in this process (23). Based on in vivo photo-cross-linking experiments, LPS molecules appear to cross the periplasm inside the ␤ jellyroll of LptC and LptA (9).…”

mentioning

confidence: 99%

Functional Interaction between the Cytoplasmic ABC Protein LptB and the Inner Membrane LptC Protein, Components of the Lipopolysaccharide Transport Machinery in Escherichia coli

et al. 2016

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The assembly of lipopolysaccharide (LPS) in the outer leaflet of the outer membrane (OM) requires the transenvelope Lpt (lipopolysaccharide transport) complex, made in Escherichia coli of seven essential proteins located in the inner membrane (IM) (LptBCFG), periplasm (LptA), and OM (LptDE). At the IM, LptBFG constitute an unusual ATP binding cassette (ABC) transporter, composed by the transmembrane LptFG proteins and the cytoplasmic LptB ATPase, which is thought to extract LPS from the IM and to provide the energy for its export across the periplasm to the cell surface. LptC is a small IM bitopic protein that binds to LptBFG and recruits LptA via its N-and C-terminal regions, and its role in LPS export is not completely understood. Here, we show that the expression level of lptB is a critical factor for suppressing lethality of deletions in the C-terminal region of LptC and the functioning of a hybrid Lpt machinery that carries Pa-LptC, the highly divergent LptC orthologue from Pseudomonas aeruginosa. We found that LptB overexpression stabilizes C-terminally truncated LptC mutant proteins, thereby allowing the formation of a sufficient amount of stable IM complexes to support growth. Moreover, the LptB level seems also critical for the assembly of IM complexes carrying Pa-LptC which is otherwise defective in interactions with the E. coli LptFG components. Overall, our data suggest that LptB and LptC functionally interact and support a model whereby LptB plays a key role in the assembly of the Lpt machinery. IMPORTANCEThe asymmetric outer membrane (OM) of Gram-negative bacteria contains in its outer leaflet an unusual glycolipid, the lipopolysaccharide (LPS). LPS largely contributes to the peculiar permeability barrier properties of the OM that prevent the entry of many antibiotics, thus making Gram-negative pathogens difficult to treat. In Escherichia coli the LPS transporter (the Lpt machine) is made of seven essential proteins (LptABCDEFG) that form a transenvelope complex. Here, we show that increased expression of the membrane-associated ABC protein LptB can suppress defects of LptC, which participates in the formation of the periplasmic bridge. This reveals functional interactions between these two components and supports a role of LptB in the assembly of the Lpt machine.

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Protease homolog BepA (YfgC) promotes assembly and degradation of β-barrel membrane proteins in Escherichia coli

Cited by 67 publications

References 52 publications

Insights into the Function of YciM, a Heat Shock Membrane Protein Required To Maintain Envelope Integrity in Escherichia coli

Insights into the Function of YciM, a Heat Shock Membrane Protein Required To Maintain Envelope Integrity in Escherichia coli

Lipopolysaccharide transport and assembly at the outer membrane: the PEZ model

Functional Interaction between the Cytoplasmic ABC Protein LptB and the Inner Membrane LptC Protein, Components of the Lipopolysaccharide Transport Machinery in Escherichia coli

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