The antibacterial toxin colicin <scp>N</scp> binds to the inner core of lipopolysaccharide and close to its translocator protein

Johnson, Christopher L.; Ridley, Helen; Marchetti, Roberta; Silipo, Alba; Griffin, David C.; Crawford, Lucy; Bonev, Boyan B.; Molinaro, Antonio; Lakey, Jeremy H.

doi:10.1111/mmi.12568

Cited by 39 publications

(35 citation statements)

References 59 publications

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“…This less dense environment of O-antigen polysaccharides above OmpF pores may be exploited by the antibacterial toxin colicin-N. Such situations provide support for the hypothetical model of colicin-N binding to core sugars envisaged by Johnson et al (19), because the gap in the FIGURE 5 Interaction patterns of OmpF protein residues with their surrounding environments in K12-lps0. The graph shows, for each residue, the frequency of interactions with another monomer (gray), water molecules (blue), a phospholipid headgroup (yellow), a phospholipid carbon tail (green), a lipid A tail (dark green), a lipid A headgroup (orange), the LPS inner core (cyan), or the LPS outer core (red).…”

Section: Biophysical Journal 110(4) 930-938mentioning

confidence: 59%

“…2 A) (14,15). Similarly, the permeability of the OM to antibiotics (18) and the binding and translocation of colicins (17,19) are influenced by bacterial surface determinants. The heterogeneity of O-antigen polysaccharide unit length and the dynamics of their constituent sugars may complicate the accessibility of mAbs to epitopes located either on the cell surface or deep within the LPS leaflet (14,20).…”

Section: Introductionmentioning

confidence: 99%

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Dynamics and Interactions of OmpF and LPS: Influence on Pore Accessibility and Ion Permeability

Patel

et al. 2016

Biophysical Journal

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The asymmetric outer membrane of Gram-negative bacteria is formed of the inner leaflet with phospholipids and the outer leaflet with lipopolysaccharides (LPS). Outer membrane protein F (OmpF) is a trimeric porin responsible for the passive transport of small molecules across the outer membrane of Escherichia coli. Here, we report the impact of different levels of heterogeneity in LPS environments on the structure and dynamics of OmpF using all-atom molecular dynamics simulations. The simulations provide insight into the flexibility and dynamics of LPS components that are highly dependent on local environments, with lipid A being the most rigid and O-antigen being the most flexible. Increased flexibility of O-antigen polysaccharides is observed in heterogeneous LPS systems, where the adjacent O-antigen repeating units are weakly interacting and thus more dynamic, compared to homogeneous LPS systems in which LPS interacts strongly with each other with limited overall flexibility due to dense packing. The model systems were validated by comparing molecular-level details of interactions between OmpF surface residues and LPS core sugars with experimental data, establishing the importance of LPS core oligosaccharides in shielding OmpF surface epitopes recognized by monoclonal antibodies. There are LPS environmental influences on the movement of bulk ions (K(+) and Cl(-)), but the ion selectivity of OmpF is mainly affected by bulk ion concentration.

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Section: Biophysical Journal 110(4) 930-938mentioning

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Dynamics and Interactions of OmpF and LPS: Influence on Pore Accessibility and Ion Permeability

Patel

et al. 2016

Biophysical Journal

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“…Polymyxins are strongly cationic lipopeptides that are likely able to replace the divalent cations bound to LPS, thus gaining access to the core of the membrane. The large antibacterial protein colicin N was recently shown to use the inner core region of LPS as its specific OM receptor, and thus must be able to access the regions of the LPS molecule close to the hydrophobic core (43). In fact, colicin N is the only molecule known to displace tightly bound LPS from the outside of the OmpF trimer (18).…”

Section: Discussionmentioning

confidence: 99%

Gram-negative trimeric porins have specific LPS binding sites that are essential for porin biogenesis

Arunmanee

Pathania

Solovyova

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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112

101

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The outer membrane (OM) of gram-negative bacteria is an unusual asymmetric bilayer with an external monolayer of lipopolysaccharide (LPS) and an inner layer of phospholipids. The LPS layer is rigid and stabilized by divalent cation cross-links between phosphate groups on the core oligosaccharide regions. This means that the OM is robust and highly impermeable to toxins and antibiotics. During their biogenesis, OM proteins (OMPs), which function as transporters and receptors, must integrate into this ordered monolayer while preserving its impermeability. Here we reveal the specific interactions between the trimeric porins of Enterobacteriaceae and LPS. Isolated porins form complexes with variable numbers of LPS molecules, which are stabilized by calcium ions. In earlier studies, two high-affinity sites were predicted to contain groups of positively charged side chains. Mutation of these residues led to the loss of LPS binding and, in one site, also prevented trimerization of the porin, explaining the previously observed effect of LPS mutants on porin folding. The high-resolution X-ray crystal structure of a trimeric porin-LPS complex not only helps to explain the mutagenesis results but also reveals more complex, subtle porin-LPS interactions and a bridging calcium ion.gram-negative bacteria | lipopolysaccharide | X-ray crystal structure | porin | outer membrane

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“…For example, liposaccharides have been reported to play ar ole in both OM protein insertion and colicin translocation. [41,42] Our discoveryw ill allow us to determinew hether protein components of these more realistic PLBs are in their natural orientations.…”

Section: Discussionmentioning

confidence: 99%

Orientation of the OmpF Porin in Planar Lipid Bilayers

et al. 2017

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The outer-membrane protein OmpF is an abundant trimeric general diffusion porin that plays a central role in the transport of antibiotics and colicins across the outer membrane of E. coli. Individual OmpF trimers in planar lipid bilayers (PLBs) show one of two current-voltage asymmetries, thus implying that insertion occurs with either the periplasmic or the extracellular end first. A method for establishing the orientation of OmpF in PLB was developed, based on targeted covalent modification with membrane-impermeant reagents of peripheral cysteine residues introduced near the periplasmic or the extracellular entrance. By correlating the results of the modification experiments with measurements of current asymmetry or the sidedness of binding of the antibiotic enrofloxacin, OmpF orientation could be quickly determined in subsequent experiments under a variety of conditions. Our work will allow the precise interpretation of past and future studies of antibiotic permeation and protein translocation through OmpF and related porins.

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The antibacterial toxin colicin N binds to the inner core of lipopolysaccharide and close to its translocator protein

Cited by 39 publications

References 59 publications

Dynamics and Interactions of OmpF and LPS: Influence on Pore Accessibility and Ion Permeability

Dynamics and Interactions of OmpF and LPS: Influence on Pore Accessibility and Ion Permeability

Gram-negative trimeric porins have specific LPS binding sites that are essential for porin biogenesis

Orientation of the OmpF Porin in Planar Lipid Bilayers

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