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5. Inhibition of transcription in Staphylococcus aureus by a primary sigma factor-binding polypeptide from phage G1

Author

Dehbi, Mohammed, Moeck, Gregory, Arhin, Francis F., Bauda, Pascale, Bergeron, Dominique, Kwan, Tony, Liu, Jing, McCarty, John, DuBow, Michael, and Pelletier, Jerry

Subjects
Staphylococcus aureus -- Genetic aspects, Staphylococcus aureus -- Research, Genetic transcription -- Research, Polypeptides -- Physiological aspects, Polypeptides -- Genetic aspects, Polypeptides -- Research, RNA polymerases -- Research, Bacteriophages -- Genetic aspects, Bacteriophages -- Research, Bacterial genetics -- Reports, Biological sciences
Abstract

The primary sigma factor of Staphylococcus aureus, [[sigma].sup.SA], regulates the transcription of many genes, including several essential genes, in this bacterium via specific recognition of exponential growth phase promoters. In this study, we report the existence of a novel staphylococcal phage G1-derived growth inhibitory polypeptide, referred to as G1ORF67, that interacts with [[sigma].sup.SA] both in vivo and in vitro and regulates its activity. Delineation of the minimal domain of [[sigma].sup.SA] that is required for its interaction with G1ORF67 as amino acids 294 to 360 near the carboxy terminus suggests that the G1 phage-encoded anti-[sigma] factor may occlude the -35 element recognition domain of [[sigma].sup.SA]. AS would be predicted by this hypothesis, the G1ORF67 polypeptide abolished both RNA polymerase core-dependent binding of [[sigma].sup.SA] to DNA and [[sigma].sup.SA]-dependent transcription in vitro. While G1ORF67 profoundly inhibits transcription when expressed in S. aureus cells in mode of action studies, our finding that G1ORF67 was unable to inhibit transcription when expressed in Escherichia coli concurs with its inability to inhibit transcription by the E. coli holoenzyme in vitro. These features demonstrate the selectivity of G1ORF67 for S. aureus RNA polymerase. We predict that G1ORF67 is one of the central polypeptides in the phage G1 strategy to appropriate host RNA polymerase and redirect it to phage reproduction.

Published
2009

6. Microbiological Characterization of VNRX-5236, a Broad-Spectrum β-Lactamase Inhibitor for Rescue of the Orally Bioavailable Cephalosporin Ceftibuten as a Carbapenem-Sparing Agent against Strains of Enterobacterales Expressing Extended-Spectrum β-Lactamases and Serine Carbapenemases

Author

Chatwin, Cassandra L., primary, Hamrick, Jodie C., additional, Trout, Robert E. L., additional, Myers, Cullen L., additional, Cusick, Susan M., additional, Weiss, William J., additional, Pulse, Mark E., additional, Xerri, Luigi, additional, Burns, Christopher J., additional, Moeck, Gregory, additional, Daigle, Denis M., additional, John, Kaitlyn, additional, Uehara, Tsuyoshi, additional, and Pevear, Daniel C., additional

Published
2021
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8. Characterization of in vitro interactions between a truncated TonB protein from Escherichia coli and the outer membrane receptors FhuA and FepA

Author

Moeck, Gregory S. and Letellier, Lucienne

Subjects
Escherichia coli -- Physiological aspects, Membrane proteins -- Physiological aspects, Protein metabolism -- Physiological aspects, Cell receptors -- Physiological aspects, Biological sciences
Abstract

The coupling of proton motive force to iron chelate receptors is mediated by TonB protein during gram-negative bacterial iron uptake process. Results indicate that TonB preferentially interacts with the ligand-loaded FhuA ferrichrome-iron receptor than the ferric enterobactin receptor FepA.

Published
2001

9. Stability studies of FhuA, a two-domain outer membrane protein from Escherichia coli

Author

Bonhivers, Melanie, Desmadril, Michel, Moeck, Gregory S., Boulanger, Pascale, Colomer-Pallas, Anne, and Letellier, Lucienne

Subjects
Bacterial proteins -- Research, Membrane proteins -- Research, Proteins -- Structure, Biological sciences, Chemistry
Abstract

A globular domain inside the beta-barrel of the E. coli membrane protein FhuA appears to be necessary for stabilizing the protein. The globular domain occludes most of the barrel and its exact function is unknown.

Published
2001

12. Topological analysis of the Escherichia coli ferrichrome-iron receptor by using monoclonal antibodies

Author

Moeck, Gregory S., Ratcliffe, Michael J.H., and Coulton, James W.

Subjects
Escherichia coli -- Genetic aspects, Monoclonal antibodies -- Research, Biological sciences
Abstract

Thirty-five monoclonal antibodies (MAbs) which inhibit the activity of outer membrane receptor FhuA, which stimulates transfer of ferrichrome-iron in Escherichia coli, were identified to analyze the surface accessibility of FhuA sequences and their effect on ligand binding. Some MAbs were able to stop cell death by colicin M and were partly able to prevent the inactivation of T5 phage. Findings indicate that most FhuA sequences have a barely accessible linear sequence.

Published
1995

13. Genetic insertion and exposure of a reporter epitope in the ferrichrome-iron receptor of Escherichia coli K-12

Author

Moeck, Gregory S., Bazzaz, B.S. Fazly, Gras, Marie France, Ravi, Tarsem S., Ratcliffe, Michael J.H., and Coulton, James W.

Subjects
Escherichia coli -- Genetic aspects, Translocation (Genetics) -- Analysis, Biological sciences
Abstract

C3 epitope insertion mutagenesis reveals the presence of 16 FhuA. C3 proteins in the ferrichrome-iron receptor of Escherichia coli K-12. The chimeric proteins are well-localized and the wild-type FhuA protein structure is not altered by C3 insertion. Twelve of the 16 strains expressing FhuA.C3 proteins display high ferrichrome transport competence. Epitope insertion mutagenesis involves splicing of foreign antigenic determinant into different sites within a protein and the identification of a permissive site that is tolerated by the protein.

Published
1994

38. Bisphosphonated Benzoxazinorifamycin Prodrugs for the Prevention and Treatment of Osteomyelitis

Author

Reddy, Ranga, primary, Dietrich, Evelyne, additional, Lafontaine, Yanick, additional, Houghton, Tom J., additional, Belanger, Odette, additional, Dubois, Anik, additional, Arhin, Francis F., additional, Sarmiento, Ingrid, additional, Fadhil, Ibtihal, additional, Laquerre, Karine, additional, Ostiguy, Valerie, additional, Lehoux, Dario, additional, Moeck, Gregory, additional, Parr, Thomas R., additional, and Rafai Far, Adel, additional

Published
2008
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39. Linking Bisphosphonates to the Free Amino Groups in Fluoroquinolones: Preparation of Osteotropic Prodrugs for the Prevention of Osteomyelitis

Author

Houghton, Tom J., primary, Tanaka, Kelly S. E., additional, Kang, Ting, additional, Dietrich, Evelyne, additional, Lafontaine, Yanick, additional, Delorme, Daniel, additional, Ferreira, Sandra S., additional, Viens, Frederic, additional, Arhin, Francis F., additional, Sarmiento, Ingrid, additional, Lehoux, Dario, additional, Fadhil, Ibtihal, additional, Laquerre, Karine, additional, Liu, Jing, additional, Ostiguy, Valérie, additional, Poirier, Hugo, additional, Moeck, Gregory, additional, Parr, Thomas R., additional, and Far, Adel Rafai, additional

Published
2008
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46. TonB-dependent iron acquisition: mechanisms of siderophore-mediated active transport†.

Author

Moeck, Gregory S and Coulton, James W

Subjects
*IRON, *CELL membranes, *IRON chelates, *ABSORPTION
Abstract

Cells growing in aerobic environments have developed intricate strategies to overcome the scarcity of iron, an essential nutrient. In Gram-negative bacteria, high-affinity iron acquisition requires outer membrane-localized proteins that bind iron chelates at the cell surface and promote their uptake. Transport of bound chelates across the outer membrane depends upon TonB–ExbB–ExbD, a cytoplasmic membrane-localized complex that transduces energy from the proton motive force to high-affinity receptors in the outer membrane. Upon ligand binding to iron chelate receptors, conformational changes are induced, some of which are detected in the periplasm. These structural alterations signal the ligand-loaded status of the receptor and, therefore, the requirement for TonB-dependent energy transduction. Thus, TonB interacts preferentially and directly with ligand-loaded receptors. Such a mechanism ensures the productive use of cellular energy to drive active transport at the outer membrane. [ABSTRACT FROM AUTHOR]

Published
1998
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47. TonB-dependent iron acquisition: mechanisms of siderophore-mediated active transport†.

Author

Moeck, Gregory S and Coulton, James W

Subjects
IRON, CELL membranes, IRON chelates, ABSORPTION
Abstract

Cells growing in aerobic environments have developed intricate strategies to overcome the scarcity of iron, an essential nutrient. In Gram-negative bacteria, high-affinity iron acquisition requires outer membrane-localized proteins that bind iron chelates at the cell surface and promote their uptake. Transport of bound chelates across the outer membrane depends upon TonB–ExbB–ExbD, a cytoplasmic membrane-localized complex that transduces energy from the proton motive force to high-affinity receptors in the outer membrane. Upon ligand binding to iron chelate receptors, conformational changes are induced, some of which are detected in the periplasm. These structural alterations signal the ligand-loaded status of the receptor and, therefore, the requirement for TonB-dependent energy transduction. Thus, TonB interacts preferentially and directly with ligand-loaded receptors. Such a mechanism ensures the productive use of cellular energy to drive active transport at the outer membrane. [ABSTRACT FROM AUTHOR]

Published
1998
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48. Oritavancin Kills Stationary-Phase and Biofilm Staphylococcus aureusCells In Vitro

Author

Belley, Adam, Neesham-Grenon, Eve, McKay, Geoffrey, Arhin, Francis F., Harris, Robert, Beveridge, Terry, Parr, Thomas R., and Moeck, Gregory

Abstract

ABSTRACTSlow-growing bacteria and biofilms are notoriously tolerant to antibiotics. Oritavancin is a lipoglycopeptide with multiple mechanisms of action that contribute to its bactericidal action against exponentially growing gram-positive pathogens, including the inhibition of cell wall synthesis and perturbation of membrane barrier function. We sought to determine whether oritavancin could eradicate cells known to be tolerant to many antimicrobial agents, that is, stationary-phase and biofilm cultures of Staphylococcus aureusin vitro. Oritavancin exhibited concentration-dependent bactericidal activity against stationary-phase inocula of methicillin-susceptible S. aureus(MSSA) ATCC 29213, methicillin-resistant S. aureus(MRSA) ATCC 33591, and vancomycin-resistant S. aureus(VRSA) VRS5 inoculated into nutrient-depleted cation-adjusted Mueller-Hinton broth. As has been described for exponential-phase cells, oritavancin induced membrane depolarization, increased membrane permeability, and caused ultrastructural defects including a loss of nascent septal cross walls in stationary-phase MSSA. Furthermore, oritavancin sterilized biofilms of MSSA, MRSA, and VRSA at minimal biofilm eradication concentrations (MBECs) of between 0.5 and 8 μg/ml. Importantly, MBECs for oritavancin were within 1 doubling dilution of their respective planktonic broth MICs, highlighting the potency of oritavancin against biofilms. These results demonstrate a significant activity of oritavancin against S. aureusin phases of growth that exhibit tolerance to other antimicrobial agents.

Published
2009
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49. Ultrastructural Effects of Oritavancin on Methicillin-Resistant Staphylococcus aureusand Vancomycin-Resistant Enterococcus

Author

Belley, Adam, Harris, Robert, Beveridge, Terry, Parr, Tom, and Moeck, Gregory

Abstract

ABSTRACTThe ultrastructural effects of the lipoglycopeptide oritavancin on methicillin-resistant Staphylococcus aureus(MRSA) and vancomycin-resistant enterococcus (VRE) were examined by transmission electron microscopy. Oritavancin but not vancomycin induced aberrant septum formation and loss of staining of nascent septal cross walls in MRSA. Septal distortions were also observed in VRE exposed to oritavancin.

Published
2009
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50. An 8-Å Projected Structure of FhuA, A “Ligand-Gated” Channel of the Escherichia coliOuter Membrane

Author

Lambert, Olivier, Moeck, Gregory S., Levy, Daniel, Plançon, Laure, Letellier, Lucienne, and Rigaud, Jean Louis

Abstract

The structure of FhuA, a siderophore and phage receptor in the outer membrane of Escherichia coli,has been investigated by electron crystallography. Bidimensional crystals of hexahistidine-tagged FhuA protein solubilized in N,N-dimethyldodecylamine-N-oxide were produced after detergent removal with polystyrene beads. Frozen-hydrated crystals (unit cell dimensions of a=124 Å, b=98 Å, γ=90°) exhibited a p22121plane group symmetry. A projection map at 8 Å resolution showed the presence of dimeric ring-like structures with an elliptical shape (48×40 Å). Each monomer was composed of a ring of densities with a radial width of 8–10 Å corresponding to a cylinder of β sheets. Few densities are present inside the barrel, leaving a central channel approximately 25 Å in diameter. A projection map of FhuA at 15 Å resolution, which was calculated from negatively stained preparations, demonstrated that most of the central channel was masked by extramembrane domains. This map also revealed an asymmetric distribution of extramembrane domains in FhuA, with large domains located mainly on one side of the molecule. Comparison with density maps derived from recent atomic structure allowed further interpretation of the electron microscopy projection structures with regard to long hydrophilic loops governing the selectivity and opening of the channel.

Published
1999
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