Proton motive force involved in protein transport across the outer membrane of Aeromonas salmonicida

Science ◽  
1989 ◽  
Vol 246 (4930) ◽  
pp. 654-656 ◽  
Author(s):  
K. Wong ◽  
J. Buckley
Keyword(s):  
Outer Membrane ◽  
Protein Transport ◽  
Proton Motive Force ◽  
Aeromonas Salmonicida ◽  
Motive Force

scholarly journals Mechanism of Bactericidal Activity of Microcin L inEscherichia coliandSalmonella enterica

2010 ◽  
Vol 55 (3) ◽  
pp. 997-1007 ◽  
Author(s):  
Natacha Morin ◽  
Isabelle Lanneluc ◽  
Nathalie Connil ◽  
Marie Cottenceau ◽  
Anne Marie Pons ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Bactericidal Activity ◽  
Salmonella Enterica ◽  
Cytoplasmic Membrane ◽  
Genetic System ◽  
Proton Motive Force ◽  
Motive Force ◽  
Membrane Properties ◽  
Outer Membrane Receptor ◽  
E Coli

ABSTRACTFor the first time, the mechanism of action of microcin L (MccL) was investigated in live bacteria. MccL is a gene-encoded peptide produced byEscherichia coliLR05 that exhibits a strong antibacterial activity against relatedEnterobacteriaceae, includingSalmonella entericaserovars Typhimurium and Enteritidis. We first subcloned the MccL genetic system to remove the sequences not involved in MccL production. We then optimized the MccL purification procedure to obtain large amounts of purified microcin to investigate its antimicrobial and membrane properties. We showed that MccL did not induce outer membrane permeabilization, which indicated that MccL did not use this way to kill the sensitive cell or to enter into it. Using a set ofE. coliandSalmonella entericamutants lacking iron-siderophore receptors, we demonstrated that the MccL uptake required the outer membrane receptor Cir. Moreover, the MccL bactericidal activity was shown to depend on the TonB protein that transduces the proton-motive force of the cytoplasmic membrane to transport iron-siderophore complexes across the outer membrane. Using carbonyl cyanide 3-chlorophenylhydrazone, which is known to fully dissipate the proton-motive force, we proved that the proton-motive force was required for the bactericidal activity of MccL onE. coli. In addition, we showed that a primary target of MccL could be the cytoplasmic membrane: a high level of MccL disrupted the inner membrane potential ofE. colicells. However, no permeabilization of the membrane was detected.

scholarly journals The TonB Dimeric Crystal Structures Do Not Exist In Vivo

mBio ◽  
2010 ◽  
Vol 1 (5) ◽  
Author(s):  
Kathleen Postle ◽  
Kyle A. Kastead ◽  
Michael G. Gresock ◽  
Joydeep Ghosh ◽  
Cheryl D. Swayne
Keyword(s):  
Outer Membrane ◽  
Crystal Structures ◽  
Cytoplasmic Membrane ◽  
Proton Motive Force ◽  
Membrane Transporters ◽  
Motive Force ◽  
Carboxy Terminus ◽  
Tonb System ◽  
Outer Membrane Transporters

ABSTRACTThe TonB system energizes transport of nutrients across the outer membrane ofEscherichia coliusing cytoplasmic membrane proton motive force (PMF) for energy. Integral cytoplasmic membrane proteins ExbB and ExbD appear to harvest PMF and transduce it to TonB. The carboxy terminus of TonB then physically interacts with outer membrane transporters to allow translocation of ligands into the periplasmic space. The structure of the TonB carboxy terminus (residues ~150 to 239) has been solved several times with similar results. Our previous results hinted thatin vitrostructures might not mimic the dimeric conformations that characterize TonBin vivo. To test structural predictions and to identify irreplaceable residues, the entire carboxy terminus of TonB was scanned with Cys substitutions. TonB I232C and N233C, predicted to efficiently form disulfide-linked dimers in the crystal structures, did not do so. In contrast, Cys substitutions positioned at large distances from one another in the crystal structures efficiently formed dimers. Cys scanning identified seven functionally important residues. However, no single residue was irreplaceable. The phenotypes conferred by changes of the seven residues depended on both the specific assay used and the residue substituted. All seven residues were synergistic with one another. The buried nature of the residues in the structures was also inconsistent with these properties. Taken together, these results indicate that the solved dimeric crystal structures of TonB do not exist. The most likely explanation for the aberrant structures is that they were obtained in the absence of the TonB transmembrane domain, ExbB, ExbD, and/or the PMF.IMPORTANCEThe TonB system of Gram-negative bacteria is an attractive target for development of novel antibiotics because of its importance in iron acquisition and virulence. Logically, therefore, the structure of TonB must be accurately understood. TonB functions as a dimerin vivo, and two different but similar crystal structures of the dimeric carboxy-terminal ~90 amino acids gave rise to mechanistic models. Here we demonstrate that the crystal structures, and therefore the models based on them, are not biologically relevant. The idiosyncratic phenotypes conferred by substitutions at the only seven functionally important residues in the carboxy terminus suggest that similar to interaction of cytochromes P450 with numerous substrates, these residues allow TonB to differentially interact with different outer membrane transporters. Taken together, data suggest that TonB is maintained poised between order and disorder by ExbB, ExbD, and the proton motive force (PMF) before energy transduction to the outer membrane transporters.

scholarly journals The quantitative basis for the redistribution of immobile bacterial lipoproteins to division septa

2021 ◽  
Vol 17 (12) ◽  
pp. e1009756
Author(s):  
Lara Connolley ◽  
Joanna Szczepaniak ◽  
Colin Kleanthous ◽  
Seán M. Murray
Keyword(s):  
Outer Membrane ◽  
Physical Mechanism ◽  
Underlying Mechanism ◽  
Proton Motive Force ◽  
Motive Force ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Division Site ◽  
Quantitative Basis ◽  
Mutant Phenotypes

The spatial localisation of proteins is critical for most cellular function. In bacteria, this is typically achieved through capture by established landmark proteins. However, this requires that the protein is diffusive on the appropriate timescale. It is therefore unknown how the localisation of effectively immobile proteins is achieved. Here, we investigate the localisation to the division site of the slowly diffusing lipoprotein Pal, which anchors the outer membrane to the cell wall of Gram-negative bacteria. While the proton motive force-linked TolQRAB system is known to be required for this repositioning, the underlying mechanism is unresolved, especially given the very low mobility of Pal. We present a quantitative, mathematical model for Pal relocalisation in which dissociation of TolB-Pal complexes, powered by the proton motive force across the inner membrane, leads to the net transport of Pal along the outer membrane and its deposition at the division septum. We fit the model to experimental measurements of protein mobility and successfully test its predictions experimentally against mutant phenotypes. Our model not only explains a key aspect of cell division in Gram-negative bacteria, but also presents a physical mechanism for the transport of low-mobility proteins that may be applicable to multi-membrane organelles, such as mitochondria and chloroplasts.

scholarly journals Chained Structure of Dimeric F 1 -like ATPase in Mycoplasma mobile Gliding Machinery

mBio ◽  
2021 ◽  
Author(s):  
Takuma Toyonaga ◽  
Takayuki Kato ◽  
Akihiro Kawamoto ◽  
Noriyuki Kodera ◽  
Tasuku Hamaguchi ◽  
...  
Keyword(s):  
Protein Transport ◽  
Protein Complexes ◽  
Proton Motive Force ◽  
Pathogenic Bacterium ◽  
Motive Force ◽  
Content Type ◽  
Homologous Protein

F 1 F o -ATPase, a rotary ATPase, is widespread in the membranes of mitochondria, chloroplasts, and bacteria and converts ATP energy with a proton motive force across the membrane by its physical rotation. Homologous protein complexes play roles in ion and protein transport. Mycoplasma mobile , a pathogenic bacterium, was recently suggested to have a special motility system evolutionarily derived from F 1 -ATPase.

scholarly journals Passive receptor dissociation driven by porin threading establishes active colicin transport through Escherichia coli OmpF

2021 ◽  
Author(s):  
Marie-Louise R Francis ◽  
Melissa N Webby ◽  
Nicholas G Housden ◽  
Renata Kaminska ◽  
Emma Elliston ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Proton Motive Force ◽  
Motive Force ◽  
Primary Receptor ◽  
Bacterial Outer Membrane ◽  
Colicin E9 ◽  
Competition For Resources

Bacteria deploy weapons to kill their neighbours during competition for resources and aid survival within microbiomes. Colicins were the first antibacterial system identified yet how these bacteriocins cross the outer membrane of Escherichia coli is unknown. Here, by solving the structures of translocation intermediates and imaging toxin import, we uncover the mechanism by which the Tol-dependent nuclease colicin E9 (ColE9) crosses the outer membrane. We show that threading of ColE9s disordered domain through two pores of the trimeric porin OmpF causes the colicin to disengage from its primary receptor, BtuB, and reorganise the translocon either side of the membrane. These rearrangements prime the toxin for import through the lumen of a single OmpF subunit, which is driven by the proton motive force-linked TolQ-TolR-TolA-TolB assembly. Our study explains why OmpF is a better translocator than OmpC and reconciles the mechanisms by which Ton- and Tol-dependent bacteriocins cross the bacterial outer membrane.

scholarly journals Specific cardiolipin-SecY interactions are required for proton-motive-force stimulation of protein secretion

2017 ◽  
Author(s):  
Robin A. Corey ◽  
Euan Pyle ◽  
William J. Allen ◽  
Marina Casiraghi ◽  
Bruno Miroux ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Protein Secretion ◽  
Binding Sites ◽  
Protein Transport ◽  
Proton Motive Force ◽  
Lipid Binding ◽  
Proton Exchange ◽  
Motive Force ◽  
Coarse Grained ◽  
Stimulation Of

AbstractThe transport of proteins across or into membranes is a vital biological process, achieved in every cell by the conserved Sec machinery. In bacteria, SecYEG combines with the SecA motor protein for secretion of pre-proteins across the plasma membrane, powered by ATP hydrolysis and the trans-membrane proton-motive-force (PMF). The activities of SecYEG and SecA are modulated by membrane lipids, particularly by cardiolipin, a specialised phospholipid known to associate with a range of energy-transducing machines. Here, we identify two specific cardiolipin binding sites on the Thermotoga maritima SecA-SecYEG complex, through application of coarse-grained molecular dynamics simulations. We validate the computational data and demonstrate the conserved nature of the binding sites using in vitro mutagenesis, native mass spectrometry and biochemical analysis of Escherichia coli SecYEG. The results show that the two sites account for the preponderance of functional cardiolipin binding to SecYEG, and mediate its roles in ATPase and protein transport activity. In addition, we demonstrate an important role for cardiolipin in the conferral of PMF-stimulation of protein transport. The apparent transient nature of the CL interaction might facilitate proton exchange with the Sec machinery and thereby stimulate protein transport, by an as yet unknown mechanism. This study demonstrates the power of coupling the high predictive ability of coarse-grained simulation with experimental analyses, towards investigation of both the nature and functional implications of protein-lipid interactions.Significance StatementMany proteins are located in lipid membranes surrounding cells and cellular organelles. The membrane can impart important structural and functional effects on the protein, making understanding of this interaction critical. Here, we apply computational simulation to the identification of conserved lipid binding sites on an important highly conserved bacterial membrane protein, the Sec translocase (SecA-SecYEG), which uses ATP and the proton motive force (PMF) to secrete proteins across the bacterial plasma membrane. We experimentally validate and reveal the conserved nature of these binding sites, and use functional analyses to investigate the biological significance of this interaction. We demonstrate that these interactions are specific, transient, and critical for both ATP- and PMF- driven protein secretion.

scholarly journals Specific cardiolipin–SecY interactions are required for proton-motive force stimulation of protein secretion

2018 ◽  
Vol 115 (31) ◽  
pp. 7967-7972 ◽  
Author(s):  
Robin A. Corey ◽  
Euan Pyle ◽  
William J. Allen ◽  
Daniel W. Watkins ◽  
Marina Casiraghi ◽  
...  
Keyword(s):  
Binding Sites ◽  
Protein Transport ◽  
Membrane Lipids ◽  
Proton Motive Force ◽  
Proton Exchange ◽  
Motive Force ◽  
Coarse Grained ◽  
In Vitro Mutagenesis ◽  
Stimulation Of

The transport of proteins across or into membranes is a vital biological process, achieved in every cell by the conserved Sec machinery. In bacteria, SecYEG combines with the SecA motor protein for secretion of preproteins across the plasma membrane, powered by ATP hydrolysis and the transmembrane proton-motive force (PMF). The activities of SecYEG and SecA are modulated by membrane lipids, particularly cardiolipin (CL), a specialized phospholipid known to associate with a range of energy-transducing machines. Here, we identify two specific CL binding sites on the Thermotoga maritima SecA–SecYEG complex, through application of coarse-grained molecular dynamics simulations. We validate the computational data and demonstrate the conserved nature of the binding sites using in vitro mutagenesis, native mass spectrometry, biochemical analysis, and fluorescence spectroscopy of Escherichia coli SecYEG. The results show that the two sites account for the preponderance of functional CL binding to SecYEG, and mediate its roles in ATPase and protein transport activity. In addition, we demonstrate an important role for CL in the conferral of PMF stimulation of protein transport. The apparent transient nature of the CL interaction might facilitate proton exchange with the Sec machinery, and thereby stimulate protein transport, by a hitherto unexplored mechanism. This study demonstrates the power of coupling the high predictive ability of coarse-grained simulation with experimental analyses, toward investigation of both the nature and functional implications of protein–lipid interactions.

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