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Tamer YT, Gaszek I, Rodrigues M, Coskun FS, Farid M, Koh AY, Russ W, Toprak E. The antibiotic efflux protein TolC is a highly evolvable target under colicin E1 or TLS phage selection. Mol Biol Evol 2021; 38:4493-4504. [PMID: 34175926 PMCID: PMC8476145 DOI: 10.1093/molbev/msab190] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Bacteriophages and bacterial toxins are promising antibacterial agents to treat infections caused by multidrug-resistant (MDR) bacteria. In fact, bacteriophages have recently been successfully used to treat life-threatening infections caused by MDR bacteria (Schooley RT, Biswas B, Gill JJ, Hernandez-Morales A, Lancaster J, Lessor L, Barr JJ, Reed SL, Rohwer F, Benler S, et al. 2017. Development and use of personalized bacteriophage-based therapeutic cocktails to treat a patient with a disseminated resistant Acinetobacter baumannii infection. Antimicrob Agents Chemother. 61(10); Chan BK, Turner PE, Kim S, Mojibian HR, Elefteriades JA, Narayan D. 2018. Phage treatment of an aortic graft infected with Pseudomonas aeruginosa. Evol Med Public Health. 2018(1):60–66; Petrovic Fabijan A, Lin RCY, Ho J, Maddocks S, Ben Zakour NL, Iredell JR, Westmead Bacteriophage Therapy Team. 2020. Safety of bacteriophage therapy in severe Staphylococcus aureus infection. Nat Microbiol. 5(3):465–472). One potential problem with using these antibacterial agents is the evolution of resistance against them in the long term. Here, we studied the fitness landscape of the Escherichia coli TolC protein, an outer membrane efflux protein that is exploited by a pore forming toxin called colicin E1 and by TLS phage (Pagie L, Hogeweg P. 1999. Colicin diversity: a result of eco-evolutionary dynamics. J Theor Biol. 196(2):251–261; Andersen C, Hughes C, Koronakis V. 2000. Chunnel vision. Export and efflux through bacterial channel-tunnels. EMBO Rep. 1(4):313–318; Koronakis V, Andersen C, Hughes C. 2001. Channel-tunnels. Curr Opin Struct Biol. 11(4):403–407; Czaran TL, Hoekstra RF, Pagie L. 2002. Chemical warfare between microbes promotes biodiversity. Proc Natl Acad Sci U S A. 99(2):786–790; Cascales E, Buchanan SK, Duché D, Kleanthous C, Lloubès R, Postle K, Riley M, Slatin S, Cavard D. 2007. Colicin biology. Microbiol Mol Biol Rev. 71(1):158–229). By systematically assessing the distribution of fitness effects of ∼9,000 single amino acid replacements in TolC using either positive (antibiotics and bile salts) or negative (colicin E1 and TLS phage) selection pressures, we quantified evolvability of the TolC. We demonstrated that the TolC is highly optimized for the efflux of antibiotics and bile salts. In contrast, under colicin E1 and TLS phage selection, TolC sequence is very sensitive to mutations. Finally, we have identified a large set of mutations in TolC that increase resistance of E. coli against colicin E1 or TLS phage without changing antibiotic susceptibility of bacterial cells. Our findings suggest that TolC is a highly evolvable target under negative selection which may limit the potential clinical use of bacteriophages and bacterial toxins if evolutionary aspects are not taken into account.
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Affiliation(s)
- Yusuf Talha Tamer
- Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Ilona Gaszek
- Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Marinelle Rodrigues
- Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Fatma Sevde Coskun
- Department of Immunology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Michael Farid
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Andrew Y Koh
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America.,Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - William Russ
- Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Center for Alzheimer's and Neurodegenerative Diseases, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Erdal Toprak
- Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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On mechanisms of colicin import: the outer membrane quandary. Biochem J 2018; 475:3903-3915. [PMID: 30541793 DOI: 10.1042/bcj20180477] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 11/02/2018] [Accepted: 11/12/2018] [Indexed: 01/09/2023]
Abstract
Current problems in the understanding of colicin import across the Escherichia coli outer membrane (OM), involving a range of cytotoxic mechanisms, are discussed: (I) Crystal structure analysis of colicin E3 (RNAase) with bound OM vitamin B12 receptor, BtuB, and of the N-terminal translocation (T) domain of E3 and E9 (DNAase) inserted into the OM OmpF porin, provide details of the initial interaction of the colicin central receptor (R)- and N-terminal T-domain with OM receptors/translocators. (II) Features of the translocon include: (a) high-affinity (K d ≈ 10-9 M) binding of the E3 receptor-binding R-domain E3 to BtuB; (b) insertion of disordered colicin N-terminal domain into the OmpF trimer; (c) binding of the N-terminus, documented for colicin E9, to the TolB protein on the periplasmic side of OmpF. Reinsertion of the colicin N-terminus into the second of the three pores in OmpF implies a colicin anchor site on the periplasmic side of OmpF. (III) Studies on the insertion of nuclease colicins into the cytoplasmic compartment imply that translocation proceeds via the C-terminal catalytic domain, proposed here to insert through the unoccupied third pore of the OmpF trimer, consistent with in vitro occlusion of OmpF channels by the isolated E3 C-terminal domain. (IV) Discussion of channel-forming colicins focuses mainly on colicin E1 for which BtuB is receptor and the OM TolC protein the proposed translocator. The ability of TolC, part of a multidrug efflux pump, for which there is no precedent for an import function, to provide a trans-periplasmic import pathway for colicin E1, is questioned on the basis of an unfavorable hairpin conformation of colicin N-terminal peptides inserted into TolC.
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Siroli L, Braschi G, de Jong A, Kok J, Patrignani F, Lanciotti R. Transcriptomic approach and membrane fatty acid analysis to study the response mechanisms of Escherichia coli to thyme essential oil, carvacrol, 2-(E)-hexanal and citral exposure. J Appl Microbiol 2018; 125:1308-1320. [PMID: 30028070 DOI: 10.1111/jam.14048] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 06/21/2018] [Accepted: 07/15/2018] [Indexed: 12/18/2022]
Abstract
AIMS The application of essential oils (EOs) and their components as food preservatives is promising but requires a deeper understanding of their mechanisms of action. This study aims to evaluate the effects of thyme EO, carvacrol, citral and 2-(E)-hexenal, on whole-genome gene expression (the transcriptome), as well as the fatty acid (FA) composition of the cell membranes of Escherichia coli K12. METHODS AND RESULTS Therefore, we studied the response against 1 h of exposure to sublethal concentrations of natural antimicrobials, of exponentially growing E. coli K12, using DNA microarray technology and a gas chromatographic method. The results show that treatment with a sublethal concentration of the antimicrobials strongly affects global gene expression in E. coli for all antimicrobials used. Major changes in the expression of genes involved in metabolic pathways as well as in FA biosynthesis and protection against oxidative stress were evidenced. Moreover, the sublethal treatments resulted in increased levels of unsaturated and cyclic FAs as well as an increase in the chain length compared to the controls. CONCLUSIONS The down-regulation of genes involved in aerobic metabolism indicates a shift from respiration to fermentative growth. Moreover, the results obtained suggest that the cytoplasmic membrane of E. coli is the major cellular target of EOs and their components. In addition, the key role of membrane unsaturated FAs in the response mechanisms of E. coli to natural antimicrobials has been confirmed in this study. SIGNIFICANCE AND IMPACT OF THE STUDY The transcriptomic data obtained signify a further step to understand the mechanisms of action of natural antimicrobials also when sublethal concentrations and short-term exposure. In addition, this research goes in deep correlating the transcriptomic modification with the changes in E. coli FA composition of cell membrane identified as the main target of the natural antimicrobials.
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Affiliation(s)
- L Siroli
- Department of Agricultural and Food Sciences, Alma Mater Studiorum, University of Bologna, Campus of Food Science, Cesena, Italy.,Interdipartimental Centre for Industrial Research-CIRI-AGRIFOOD, Alma Mater Studiorum, University of Bologna, Cesena (FC), Italy
| | - G Braschi
- Department of Agricultural and Food Sciences, Alma Mater Studiorum, University of Bologna, Campus of Food Science, Cesena, Italy
| | - A de Jong
- Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, AG Groningen, The Netherlands
| | - J Kok
- Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, AG Groningen, The Netherlands
| | - F Patrignani
- Department of Agricultural and Food Sciences, Alma Mater Studiorum, University of Bologna, Campus of Food Science, Cesena, Italy.,Interdipartimental Centre for Industrial Research-CIRI-AGRIFOOD, Alma Mater Studiorum, University of Bologna, Cesena (FC), Italy
| | - R Lanciotti
- Department of Agricultural and Food Sciences, Alma Mater Studiorum, University of Bologna, Campus of Food Science, Cesena, Italy.,Interdipartimental Centre for Industrial Research-CIRI-AGRIFOOD, Alma Mater Studiorum, University of Bologna, Cesena (FC), Italy
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Yang Z, Weisshaar JC. HaloTag Assay Suggests Common Mechanism of E. coli Membrane Permeabilization Induced by Cationic Peptides. ACS Chem Biol 2018; 13:2161-2169. [PMID: 29812894 DOI: 10.1021/acschembio.8b00336] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Permeabilization of the Gram-negative bacterial outer membrane (OM) by antimicrobial peptides (AMPs) is the initial step enabling access of the AMP to the cytoplasmic membrane. We present a new single-cell, time-resolved fluorescence microscopy assay that reports on the permeabilization of the E. coli OM to small molecules with a time resolution of 3 s or better. When profluorophore JF646 (702 Da) crosses the outer membrane (OM) and gains access to the periplasm, it binds to the localized HaloTag protein (34 kDa) and fluoresces in a characteristic hollow spatial pattern. Previous work used the much larger periplasmic GFP (27 kDa) probe, which reports on OM permeabilization to globular proteins. We test the assay on three cationic agents: Gellman random β-peptide copolymer MM63:CHx37, human AMP LL-37, and synthetic hybrid AMP CM15. These results combined with the previous work suggest a unifying sequence of OM and cytoplasmic membrane (CM) events that may prove commonplace in the attack of cationic peptides on Gram-negative bacteria. The peptide initially induces gradual OM permeabilization to small molecules, likely including the peptide itself. After a lag time, abrupt permeabilization of the OM, abrupt resealing of the OM, and abrupt permeabilization of the CM (all to globular proteins) occur in rapid sequence. We propose a mechanism based on membrane curvature stress induced by the time-dependent differential binding of peptide to the outer leaflet of the OM and CM. The results provide fresh insight into the critical OM-permeabilization step leading to a variety of damaging downstream events.
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Affiliation(s)
- Zhilin Yang
- Department of Chemistry and Molecular Biophysics Program University of Wisconsin—Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - James C. Weisshaar
- Department of Chemistry and Molecular Biophysics Program University of Wisconsin—Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
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The Colicin E1 TolC Box: Identification of a Domain Required for Colicin E1 Cytotoxicity and TolC Binding. J Bacteriol 2016; 199:JB.00412-16. [PMID: 27795317 DOI: 10.1128/jb.00412-16] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 10/17/2016] [Indexed: 11/20/2022] Open
Abstract
Colicins are protein toxins made by Escherichia coli to kill related bacteria that compete for scarce resources. All colicins must cross the target cell outer membrane in order to reach their intracellular targets. Normally, the first step in the intoxication process is the tight binding of the colicin to an outer membrane receptor protein via its central receptor-binding domain. It is shown here that for one colicin, E1, that step, although it greatly increases the efficiency of killing, is not absolutely necessary. For colicin E1, the second step, translocation, relies on the outer membrane/transperiplasmic protein TolC. The normal role of TolC in bacteria is as an essential component of a family of tripartite drug and toxin exporters, but for colicin E1, it is essential for its import. Colicin E1 and some N-terminal translocation domain peptides had been shown previously to bind in vitro to TolC and occlude channels made by TolC in planar lipid bilayer membranes. Here, a set of increasingly shorter colicin E1 translocation domain peptides was shown to bind to Escherichia coli in vivo and protect them from subsequent challenge by colicin E1. A segment of only 21 residues, the "TolC box," was thereby defined; that segment is essential for colicin E1 cytotoxicity and for binding of translocation domain peptides to TolC. IMPORTANCE The Escherichia coli outer membrane/transperiplasmic protein TolC is normally an essential component of the bacterium's tripartite drug and toxin export machinery. The protein toxin colicin E1 instead uses TolC for its import into the cells that it kills, thereby subverting its normal role. Increasingly shorter constructs of the colicin's N-terminal translocation domain were used to define an essential 21-residue segment that is required for both colicin cytotoxicity and for binding of the colicin's translocation domain to bacteria, in order to protect them from subsequent challenge by active colicin E1. Thus, an essential TolC binding sequence of colicin E1 was identified and may ultimately lead to the development of drugs to block the bacterial drug export pathway.
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Zakharov SD, Wang XS, Cramer WA. The Colicin E1 TolC-Binding Conformer: Pillar or Pore Function of TolC in Colicin Import? Biochemistry 2016; 55:5084-94. [PMID: 27536862 DOI: 10.1021/acs.biochem.6b00621] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The mechanism by which the drug export protein TolC is utilized for import of the cytotoxin colicin E1 across the outer membrane and periplasmic space is addressed. Studies of the initial binding of colicin E1 with TolC, occlusion of membrane-incorporated TolC ion channels, and the structure underlying the colicin-TolC complex were based on the interactions with TolC of individual colicin translocation domain (T-domain) peptides from a set of 19 that span different segments of the T-domain. These studies led to identification of a short 20-residue segment 101-120, a "TolC box", located near the center of the colicin T-domain, which is necessary for binding of colicin to TolC. Omission of this segment eliminated the ability of the T-domain to occlude TolC channels and to co-elute with TolC on a size-exclusion column. Far-ultraviolet circular dichroism spectral and thermal stability analysis of the structure of T-domain peptides implies (i) a helical hairpin conformation of the T-domain, (ii) the overlap of the TolC-binding site with a hinge of the helical hairpin, and (iii) a TolC-dependent stage of colicin import in which a central segment of the T-domain in a helical hairpin conformation binds to the TolC entry port following initial binding to the BtuB receptor. These studies provide the first structure-based information about the interaction of colicin E1 with the unique TolC protein. The model inferred for binding of the T-domain to TolC implies reservations about the traditional model for colicin import in which TolC functions to provide a channel for translocation of the colicin in an unfolded state across the bacterial outer membrane and a large part of the periplasmic space.
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Affiliation(s)
- Stanislav D Zakharov
- Department of Biological Sciences, Purdue University , Hockmeyer Building of Structural Biology, West Lafayette, Indiana 47907, United States
| | - Xin S Wang
- Department of Biological Sciences, Purdue University , Hockmeyer Building of Structural Biology, West Lafayette, Indiana 47907, United States
| | - William A Cramer
- Department of Biological Sciences, Purdue University , Hockmeyer Building of Structural Biology, West Lafayette, Indiana 47907, United States
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De Geyter J, Tsirigotaki A, Orfanoudaki G, Zorzini V, Economou A, Karamanou S. Protein folding in the cell envelope of Escherichia coli. Nat Microbiol 2016; 1:16107. [PMID: 27573113 DOI: 10.1038/nmicrobiol.2016.107] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 06/02/2016] [Indexed: 11/09/2022]
Abstract
While the entire proteome is synthesized on cytoplasmic ribosomes, almost half associates with, localizes in or crosses the bacterial cell envelope. In Escherichia coli a variety of mechanisms are important for taking these polypeptides into or across the plasma membrane, maintaining them in soluble form, trafficking them to their correct cell envelope locations and then folding them into the right structures. The fidelity of these processes must be maintained under various environmental conditions including during stress; if this fails, proteases are called in to degrade mislocalized or aggregated proteins. Various soluble, diffusible chaperones (acting as holdases, foldases or pilotins) and folding catalysts are also utilized to restore proteostasis. These responses can be general, dealing with multiple polypeptides, with functional overlaps and operating within redundant networks. Other chaperones are specialized factors, dealing only with a few exported proteins. Several complex machineries have evolved to deal with binding to, integration in and crossing of the outer membrane. This complex protein network is responsible for fundamental cellular processes such as cell wall biogenesis; cell division; the export, uptake and degradation of molecules; and resistance against exogenous toxic factors. The underlying processes, contributing to our fundamental understanding of proteostasis, are a treasure trove for the development of novel antibiotics, biopharmaceuticals and vaccines.
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Affiliation(s)
- Jozefien De Geyter
- KU Leuven-University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, B-3000 Leuven, Belgium
| | - Alexandra Tsirigotaki
- KU Leuven-University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, B-3000 Leuven, Belgium
| | - Georgia Orfanoudaki
- Institute of Molecular Biology and Biotechnology, FORTH and Department of Biology, University of Crete, PO Box 1385, GR-711 10 Iraklio, Crete, Greece
| | - Valentina Zorzini
- KU Leuven-University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, B-3000 Leuven, Belgium
| | - Anastassios Economou
- KU Leuven-University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, B-3000 Leuven, Belgium.,Institute of Molecular Biology and Biotechnology, FORTH and Department of Biology, University of Crete, PO Box 1385, GR-711 10 Iraklio, Crete, Greece
| | - Spyridoula Karamanou
- KU Leuven-University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, B-3000 Leuven, Belgium
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Burger VM, Nolasco DO, Stultz CM. Expanding the Range of Protein Function at the Far End of the Order-Structure Continuum. J Biol Chem 2016; 291:6706-13. [PMID: 26851282 PMCID: PMC4807258 DOI: 10.1074/jbc.r115.692590] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The traditional view of the structure-function paradigm is that a protein's function is inextricably linked to a well defined, three-dimensional structure, which is determined by the protein's primary amino acid sequence. However, it is now accepted that a number of proteins do not adopt a unique tertiary structure in solution and that some degree of disorder is required for many proteins to perform their prescribed functions. In this review, we highlight how a number of protein functions are facilitated by intrinsic disorder and introduce a new protein structure taxonomy that is based on quantifiable metrics of a protein's disorder.
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Affiliation(s)
- Virginia M Burger
- From the Research Laboratory for Electronics, Department of Electrical Engineering & Computer Science, and
| | - Diego O Nolasco
- From the Research Laboratory for Electronics, Department of Electrical Engineering & Computer Science, and
| | - Collin M Stultz
- From the Research Laboratory for Electronics, Department of Electrical Engineering & Computer Science, and the Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02138
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9
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Hadi-Alijanvand H, Rouhani M. Journey of poly-nucleotides through OmpF porin. J Phys Chem B 2015; 119:6113-28. [PMID: 25965338 DOI: 10.1021/acs.jpcb.5b00763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OmpF is an abundant porin in many bacteria which attracts attention as a promising biological nanopore for DNA sequencing. We study the interactions of OmpF with pentameric poly-nucleotides (poly-Ns) in silico. The poly-N molecule is forced to translocate through the lumen of OmpF. Subsequently, the structural and dynamical effects of translocation steps on protein and poly-N molecules are explored in detail. The external loops of OmpF are introduced as the main region for discrimination of poly-Ns based on their organic bases. Structural network analyses of OmpF in the presence or absence of poly-Ns characterize special residues in the structural network of porin. These residues pave the way for engineering OmpF protein. The poly-N-specific pattern of OmpF's local conductance is detected in the current study. Computing the potential of mean force for translocation steps, we define the energetic barrier ahead of poly-N to move through OmpF's lumen. We suggest that fast translocation of the examined poly-N molecules through OmpF seems unattainable by small external driving forces. Our computational results suggest some abilities for OmpF porin like OmpF's potential for being used in poly-N sequencing.
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Affiliation(s)
- Hamid Hadi-Alijanvand
- Department of Biological Sciences, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan, 45137-66731, Iran
| | - Maryam Rouhani
- Department of Biological Sciences, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan, 45137-66731, Iran
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10
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Agarwal R, Zakharov S, Hasan SS, Ryan CM, Whitelegge JP, Cramer WA. Structure-function of cyanobacterial outer-membrane protein, Slr1270: homolog of Escherichia coli drug export/colicin import protein, TolC. FEBS Lett 2014; 588:3793-801. [PMID: 25218435 PMCID: PMC4288923 DOI: 10.1016/j.febslet.2014.08.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 08/18/2014] [Accepted: 08/19/2014] [Indexed: 01/07/2023]
Abstract
Compared to thylakoid and inner membrane proteins in cyanobacteria, no structure-function information is available presently for integral outer-membrane proteins (OMPs). The Slr1270 protein from the cyanobacterium Synechocystis 6803, over-expressed in Escherichia coli, was refolded, and characterized for molecular size, secondary structure, and ion-channel function. Refolded Slr1270 displays a single band in native-electrophoresis, has an α-helical content of 50-60%, as in E. coli TolC with which it has significant secondary-structure similarity, and an ion-channel function with a single-channel conductance of 80-200pS, and a monovalent ion (K(+):Cl(-)) selectivity of 4.7:1. The pH-dependence of channel conductance implies a role for carboxylate residues in channel gating, analogous to that in TolC.
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Affiliation(s)
- Rachna Agarwal
- Department of Biological Sciences, Purdue University, West Lafayette, IN, United States; Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai, India
| | - Stanislav Zakharov
- Department of Biological Sciences, Purdue University, West Lafayette, IN, United States; Institute of Basic Problems of Biology, Russian Academy of Sciences, Puschino, Moscow Region, Russian Federation
| | - S Saif Hasan
- Department of Biological Sciences, Purdue University, West Lafayette, IN, United States
| | - Christopher M Ryan
- Pasarow Mass Spectrometry Laboratory, NPI-Semel Institute for Neuroscience and Human Behavior, UCLA, Los Angeles, CA, United States
| | - Julian P Whitelegge
- Pasarow Mass Spectrometry Laboratory, NPI-Semel Institute for Neuroscience and Human Behavior, UCLA, Los Angeles, CA, United States
| | - William A Cramer
- Department of Biological Sciences, Purdue University, West Lafayette, IN, United States.
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Kim YC, Tarr AW, Penfold CN. Colicin import into E. coli cells: a model system for insights into the import mechanisms of bacteriocins. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1717-31. [PMID: 24746518 DOI: 10.1016/j.bbamcr.2014.04.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 04/04/2014] [Accepted: 04/06/2014] [Indexed: 01/03/2023]
Abstract
Bacteriocins are a diverse group of ribosomally synthesized protein antibiotics produced by most bacteria. They range from small lanthipeptides produced by lactic acid bacteria to much larger multi domain proteins of Gram negative bacteria such as the colicins from Escherichia coli. For activity bacteriocins must be released from the producing cell and then bind to the surface of a sensitive cell to instigate the import process leading to cell death. For over 50years, colicins have provided a working platform for elucidating the structure/function studies of bacteriocin import and modes of action. An understanding of the processes that contribute to the delivery of a colicin molecule across two lipid membranes of the cell envelope has advanced our knowledge of protein-protein interactions (PPI), protein-lipid interactions and the role of order-disorder transitions of protein domains pertinent to protein transport. In this review, we provide an overview of the arrangement of genes that controls the synthesis and release of the mature protein. We examine the uptake processes of colicins from initial binding and sequestration of binding partners to crossing of the outer membrane, and then discuss the translocation of colicins through the cell periplasm and across the inner membrane to their cytotoxic site of action. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
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Affiliation(s)
- Young Chan Kim
- School of Life Sciences, University of Nottingham, Queens Medical Centre, Nottingham, NG7 2UH, UK
| | - Alexander W Tarr
- School of Life Sciences, University of Nottingham, Queens Medical Centre, Nottingham, NG7 2UH, UK
| | - Christopher N Penfold
- School of Life Sciences, University of Nottingham, Queens Medical Centre, Nottingham, NG7 2UH, UK.
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12
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Abstract
A Biochemical Society Focused Meeting on bacteriocins was held at the University of Nottingham on 16-18 July 2012 to mark the retirement of Professor Richard James and honour a scientific career of more than 30 years devoted to an understanding of the biology of colicins, bacteriocins produced by Escherichia coli. This meeting was the third leg of a triumvirate of symposia that included meetings at the Île de Bendor, France, in 1991 and the University of East Anglia, Norwich, U.K., in 1998, focused on bringing together leading experts in basic and applied bacteriocin research. The symposium which attracted 70 attendees consisted of 18 invited speakers and 22 selected oral communications spread over four themes: (i) Role of bacteriocins in bacterial ecology, (ii) Mode of action of bacteriocins, (ii) Mechanisms of bacteriocin import across the cell envelope, and (iv) Biotechnological and biomedical applications of bacteriocins. Speakers and poster presenters travelled from around the world, including the U.S.A., Japan, Asia and Europe, to showcase the latest developments in their scientific research.
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