Enzymology of lipid A palmitoylation in bacterial outer membranes

Bishop, Russell E.; Lo, Eileen I.; Khan, M. Adil; Zoeiby, Ahmed El; Jia, Wenyi

doi:10.1179/096805104225004004

Cited by 4 publications

(4 citation statements)

References 37 publications

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“…The transcription profiles between the parental CFT073 strain and the phoP mutant were compared from aerated, mid‐exponential‐phase cultures in LB medium (OD 600 = 0.6). We reasoned this would identify genes regulated directly or indirectly by PhoP because (i) LB medium is sufficiently Mg 2+ ‐limited to activate phoPQ ‐dependent gene expression (Garcia Vescovi et al ., 1996; Bishop et al ., 2004; Jia et al ., 2004), and (ii) each phoP ‐dependent phenotype was tested using bacteria cultured under these growth conditions. The microarray analysis showed that deletion of phoP resulted in the differential expression of 620 genes ( P < 0.05).…”

Section: Resultsmentioning

confidence: 99%

The broadly conserved regulator PhoP links pathogen virulence and membrane potential in Escherichia coli

Alteri

Lindner

Reiss

et al. 2011

Molecular Microbiology

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Summary PhoP is considered a virulence regulator despite being conserved in both pathogenic and non-pathogenic Enterobacteriaceae. While Escherichia coli strains represent non-pathogenic commensal isolates and numerous virulent pathotypes, the PhoP virulence regulator has only been studied in commensal E. coli. To better understand how conserved transcription factors contribute to virulence, we characterized PhoP in pathogenic E. coli. Deletion of phoP significantly attenuated E. coli during extraintestinal infection. This was not surprising since we demonstrated that PhoP differentially regulated the transcription of >600 genes. In addition to survival at acidic pH and resistance to polymyxin, PhoP was required for repression of motility and oxygen-independent changes in the expression of primary dehydrogenase and terminal reductase respiratory chain components. All phenotypes have in common a reliance on an energized membrane. Thus, we hypothesized that PhoP mediates these effects by regulating genes encoding proteins that generate proton motive force. Indeed, bacteria lacking PhoP exhibited a hyper-polarized membrane and dissipation of the transmembrane electrochemical gradient increased susceptibility of the phoP mutant to acidic pH, while inhibiting respiratory generation of the proton gradient restored resistance to antimicrobial peptides independent of lipopolysaccharide modification. These findings demonstrate a connection between PhoP, virulence, and the energized state of the membrane.

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Section: Resultsmentioning

confidence: 99%

The broadly conserved regulator PhoP links pathogen virulence and membrane potential in Escherichia coli

Alteri

Lindner

Reiss

et al. 2011

Molecular Microbiology

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“…PagP enzyme is a ␤-barrel outer membrane protein from Escherichia coli. It catalyzes the palmitate transfer from a phospholipid to a glucosamine unit of a lipid in the outer leaflet and reinforces the outer leaflet to protect E. coli from a host's immune response (19)(20)(21). PagP remains dormant when the outer membrane permeability barrier is intact but can respond adaptively and instantaneously to perturbations to restore the permeability barrier (22).…”

Section: Weakly Stable Regions In the Tm Domain And Stabilization By mentioning

confidence: 99%

Predicting weakly stable regions, oligomerization state, and protein–protein interfaces in transmembrane domains of outer membrane proteins

Naveed

Jackups

Liang

2009

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

109

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Although the structures of many ␤-barrel membrane proteins are available, our knowledge of the principles that govern their energetics and oligomerization states is incomplete. Here we describe a computational method to study the transmembrane (TM) domains of ␤-barrel membrane proteins. Our method is based on a physical interaction model, a simplified conformational space for efficient enumeration, and an empirical potential function from a detailed combinatorial analysis. Using this method, we can identify weakly stable regions in the TM domain, which are found to be important structural determinants for ␤-barrel membrane proteins. By calculating the melting temperatures of the TM strands, our method can also assess the stability of ␤-barrel membrane proteins. Predictions on membrane enzyme PagP are consistent with recent experimental NMR and mutant studies. We have also discovered that out-clamps, in-plugs, and oligomerization are 3 general mechanisms for stabilizing weakly stable TM regions. In addition, we have found that extended and contiguous weakly stable regions often signal the existence of an oligomer and that strands located in the interfaces of protein-protein interactions are considerably less stable. Based on these observations, we can predict oligomerization states and can identify the interfaces of protein-protein interactions for ␤-barrel membrane proteins by using either structure or sequence information. In a set of 25 nonhomologous proteins with known structures, our method successfully predicted whether a protein forms a monomer or an oligomer with 91% accuracy; in addition, our method identified with 82% accuracy the protein-protein interaction interfaces by using sequence information only when correct strands are given.in-plug ͉ membrane protein oligomerization ͉ out-clamp ͉ protein-protein interaction ͉ weakly stable TM strand D eveloping a general understanding of how proteins behave in membranes is of fundamental importance. ␤-barrel membrane proteins, one of the 2 major structural classes of membrane proteins, have been studied extensively. Currently, structures of 70 ␤-barrel membrane proteins have been resolved, and much has been learned about their thermodynamic stability (1), folding kinetics (2-4), biogenesis (5), and biological functions (6). These membrane proteins are thought to have very regular structures, with the basic principles of their architectural organization well understood (7). An overwhelming structural feature is the existence of an extensive regular hydrogen bond network between the transmembrane (TM) ␤-strands, which is thought to confer extreme stability on the proteins (8).However, ␤-barrel membrane proteins have diverse structures and often deviate significantly from the standard barrel architecture. For example, there are often small ␣-helices and ␤-strands, called in-plugs, found inside the ␤-barrel (9). Nonbarrel-embedded helices are also found to pack against the TM ␤-strands (10). In addition, some ␤-barrel membrane proteins exist in monomeric form, whe...

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“…Palmitate from a phospholipid is incorporated into lipid A by the outer membrane enzyme PagP. 41 The pagP gene was first identified in a Salmonella mutant that was found to be sensitive to cationic antimicrobial peptides (CAMPs), which are included among the products of the TLR4 signal transduction pathway. 13 Consequently, the modification of lipid A with a palmitate chain appears, remarkably, to both attenuate the production of CAMPs through the TLR4 pathway, and protect the bacterial pathogen from the antimicrobial products of that same pathway.…”

Section: Resultsmentioning

confidence: 99%

Role of lipid A palmitoylation in bacterial pathogenesis

Bishop¹,

Kim²,

Zoeiby³

2005

J. Endotoxin Res.

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The presence of palmitate in a minor fraction of lipid A has been known since the chemical structure of lipid A was first elucidated, but the functional importance in bacterial pathogenesis of regulated lipid A palmitoylation has become clear only recently. A palmitate chain from a phospholipid is incorporated into lipid A by an outer membrane enzyme PagP. The isolation of pagP mutants from pathogenic Gram-negative bacteria has revealed that palmitoylated lipid A can both protect the bacterium from certain host immune defenses and attenuate the ability of lipid A to activate those same defenses through the TLR4 signal transduction pathway. The mechanisms by which bacteria regulate the incorporation of palmitate into lipid A strikingly reflect the corresponding organism's pathogenic lifestyle. Variations on these themes can be illustrated with the known pagP homologs from Gram-negative bacteria, which include pathogens of humans and other mammals in addition to pathogens of insects and plants. The PagP enzyme is now lending itself both as a target for the development of anti-infective agents, and as a tool for the synthesis of lipid A-based vaccine adjuvants and endotoxin antagonists.

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Enzymology of lipid A palmitoylation in bacterial outer membranes

Cited by 4 publications

References 37 publications

The broadly conserved regulator PhoP links pathogen virulence and membrane potential in Escherichia coli

The broadly conserved regulator PhoP links pathogen virulence and membrane potential in Escherichia coli

Predicting weakly stable regions, oligomerization state, and protein–protein interfaces in transmembrane domains of outer membrane proteins

Role of lipid A palmitoylation in bacterial pathogenesis

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