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Kumar S, Lekshmi M, Stephen J, Ortiz-Alegria A, Ayitah M, Varela MF. Dynamics of efflux pumps in antimicrobial resistance, persistence, and community living of Vibrionaceae. Arch Microbiol 2023; 206:7. [PMID: 38017151 DOI: 10.1007/s00203-023-03731-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 10/30/2023] [Accepted: 11/01/2023] [Indexed: 11/30/2023]
Abstract
The marine bacteria of the Vibrionaceae family are significant from the point of view of their role in the marine geochemical cycle, as well as symbionts and opportunistic pathogens of aquatic animals and humans. The well-known pathogens of this group, Vibrio cholerae, V. parahaemolyticus, and V. vulnificus, are responsible for significant morbidity and mortality associated with a range of infections from gastroenteritis to bacteremia acquired through the consumption of raw or undercooked seafood and exposure to seawater containing these pathogens. Although generally regarded as susceptible to commonly employed antibiotics, the antimicrobial resistance of Vibrio spp. has been on the rise in the last two decades, which has raised concern about future infections by these bacteria becoming increasingly challenging to treat. Diverse mechanisms of antimicrobial resistance have been discovered in pathogenic vibrios, the most important being the membrane efflux pumps, which contribute to antimicrobial resistance and their virulence, environmental fitness, and persistence through biofilm formation and quorum sensing. In this review, we discuss the evolution of antimicrobial resistance in pathogenic vibrios and some of the well-characterized efflux pumps' contributions to the physiology of antimicrobial resistance, host and environment survival, and their pathogenicity.
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Affiliation(s)
- Sanath Kumar
- QC Laboratory, Post-Harvest Technology, ICAR-Central Institute of Fisheries Education (CIFE), Mumbai, 400061, India
| | - Manjusha Lekshmi
- QC Laboratory, Post-Harvest Technology, ICAR-Central Institute of Fisheries Education (CIFE), Mumbai, 400061, India
| | - Jerusha Stephen
- QC Laboratory, Post-Harvest Technology, ICAR-Central Institute of Fisheries Education (CIFE), Mumbai, 400061, India
| | - Anely Ortiz-Alegria
- Department of Biology, Eastern New Mexico University, Station 33, Portales, NM, 88130, USA
| | - Matthew Ayitah
- Department of Biology, Eastern New Mexico University, Station 33, Portales, NM, 88130, USA
| | - Manuel F Varela
- Department of Biology, Eastern New Mexico University, Station 33, Portales, NM, 88130, USA.
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2
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Nasr MA, Martin VJJ, Kwan DH. Divergent directed evolution of a TetR-type repressor towards aromatic molecules. Nucleic Acids Res 2023; 51:7675-7690. [PMID: 37377432 PMCID: PMC10415137 DOI: 10.1093/nar/gkad503] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 05/18/2023] [Accepted: 06/25/2023] [Indexed: 06/29/2023] Open
Abstract
Reprogramming cellular behaviour is one of the hallmarks of synthetic biology. To this end, prokaryotic allosteric transcription factors (aTF) have been repurposed as versatile tools for processing small molecule signals into cellular responses. Expanding the toolbox of aTFs that recognize new inducer molecules is of considerable interest in many applications. Here, we first establish a resorcinol responsive aTF-based biosensor in Escherichia coli using the TetR-family repressor RolR from Corynebacterium glutamicum. We then perform an iterative walk along the fitness landscape of RolR to identify new inducer specificities, namely catechol, methyl catechol, caffeic acid, protocatechuate, L-DOPA, and the tumour biomarker homovanillic acid. Finally, we demonstrate the versatility of these engineered aTFs by transplanting them into the model eukaryote Saccharomyces cerevisiae. This work provides a framework for efficient aTF engineering to expand ligand specificity towards novel molecules on laboratory timescales, which, more broadly, is invaluable across a wide range of applications such as protein and metabolic engineering, as well as point-of-care diagnostics.
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Affiliation(s)
- Mohamed A Nasr
- Centre for Applied Synthetic Biology, Concordia University, Montréal, Québec, Canada
- Department of Biology, Concordia University, Montréal, Québec, Canada
- PROTEO, Québec Network for Research on Protein Function, Structure, and Engineering, Québec City, Québec, Canada
| | - Vincent J J Martin
- Centre for Applied Synthetic Biology, Concordia University, Montréal, Québec, Canada
- Department of Biology, Concordia University, Montréal, Québec, Canada
| | - David H Kwan
- Centre for Applied Synthetic Biology, Concordia University, Montréal, Québec, Canada
- Department of Biology, Concordia University, Montréal, Québec, Canada
- Department of Chemistry and Biochemistry, Concordia University, Montréal, Québec, Canada
- PROTEO, Québec Network for Research on Protein Function, Structure, and Engineering, Québec City, Québec, Canada
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Yi X, Kazlauskas R, Travisano M. Evolutionary innovation using EDGE, a system for localized elevated mutagenesis. PLoS One 2020; 15:e0232330. [PMID: 32353078 PMCID: PMC7192385 DOI: 10.1371/journal.pone.0232330] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 04/14/2020] [Indexed: 11/19/2022] Open
Abstract
Mutations arising across the whole genome can hinder the emergence of evolutionary innovation required for adaptation because many mutations are deleterious. This trade-off is overcome by elevated mutagenesis to localized loci. Examples include phase variation and diversity-generating retroelements. However, these mechanisms are rare in nature; and all have narrow mutational spectra limiting evolutionary innovation. Here, we engineer a platform of Experimental Designed Genic Evolution (EDGE) to study the potential for evolutionary novelty at a single locus. Experimental evolution with EDGE shows that bacterial resistance to a novel antibiotic readily evolves, provided that elevated mutagenesis is focused on a relevant gene. A model is proposed to account for the cost and benefit of such single loci to adaptation in a changing environment and explains their high mutation rates, limited innovation, and the rarity of localized mutagenesis in nature. Overall, our results suggest that localized mutation systems can facilitate continuing adaptive evolution without necessarily restricting the spectrum of mutations. EDGE has utility in dissecting the complex process of adaptation with its localized, efficient evolution.
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Affiliation(s)
- Xiao Yi
- BioTechnology Institute, University of Minnesota, St. Paul, Minnesota, United States of America
| | - Romas Kazlauskas
- BioTechnology Institute, University of Minnesota, St. Paul, Minnesota, United States of America
- Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, Minnesota, United States of America
| | - Michael Travisano
- BioTechnology Institute, University of Minnesota, St. Paul, Minnesota, United States of America
- Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota, United States of America
- * E-mail:
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4
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Schaerli Y, Isalan M. Building synthetic gene circuits from combinatorial libraries: screening and selection strategies. MOLECULAR BIOSYSTEMS 2013; 9:1559-67. [DOI: 10.1039/c2mb25483b] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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5
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Gredell JA, Frei CS, Cirino PC. Protein and RNA engineering to customize microbial molecular reporting. Biotechnol J 2011; 7:477-99. [PMID: 22031507 DOI: 10.1002/biot.201100266] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Revised: 07/20/2011] [Accepted: 08/23/2011] [Indexed: 12/19/2022]
Abstract
Nature takes advantage of the malleability of protein and RNA sequence and structure to employ these macromolecules as molecular reporters whose conformation and functional roles depend on the presence of a specific ligand (an "effector" molecule). By following nature's example, ligand-responsive proteins and RNA molecules are now routinely engineered and incorporated into customized molecular reporting systems (biosensors). Microbial small-molecule biosensors and endogenous molecular reporters based on these sensing components find a variety of applications that include high-throughput screening of biosynthesis libraries, environmental monitoring, and novel gene regulation in synthetic biology. Here, we review recent advances in engineering small-molecule recognition by proteins and RNA and in coupling in vivo ligand binding to reporter-gene expression or to allosteric activation of a protein conferring a detectable phenotype. Emphasis is placed on microbial screening systems that serve as molecular reporters and facilitate engineering the ligand-binding component to recognize new molecules.
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Affiliation(s)
- Joseph A Gredell
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX, USA
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6
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Induction of multidrug resistance mechanism in Escherichia coli biofilms by interplay between tetracycline and ampicillin resistance genes. Antimicrob Agents Chemother 2009; 53:4628-39. [PMID: 19721076 DOI: 10.1128/aac.00454-09] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Biofilms gain resistance to various antimicrobial agents, and the presence of antibiotic resistance genes is thought to contribute to a biofilm-mediated antibiotic resistance. Here we showed the interplay between the tetracycline resistance efflux pump TetA(C) and the ampicillin resistance gene (bla(TEM-1)) in biofilms of Escherichia coli harboring pBR322 in the presence of the mixture of ampicillin and tetracycline. E. coli in the biofilms could obtain the high-level resistance to ampicillin, tetracycline, penicillin, erythromycin, and chloramphenicol during biofilm development and maturation as a result of the interplay between the marker genes on the plasmids, the increase of plasmid copy number, and consequently the induction of the efflux systems on the bacterial chromosome, especially the EmrY/K and EvgA/S pumps. In addition, we characterized the overexpression of the TetA(C) pump that contributed to osmotic stress response and was involved in the induction of capsular colanic acid production, promoting formation of mature biofilms. However, this investigated phenomenon was highly dependent on the addition of the subinhibitory concentrations of antibiotic mixture, and the biofilm resistance behavior was limited to aminoglycoside antibiotics. Thus, marker genes on plasmids played an important role in both resistance of biofilm cells to antibiotics and in formation of mature biofilms, as they could trigger specific chromosomal resistance mechanisms to confer a high-level resistance during biofilm formation.
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Nomura Y, Yokobayashi Y. Reengineering a natural riboswitch by dual genetic selection. J Am Chem Soc 2007; 129:13814-5. [PMID: 17944473 DOI: 10.1021/ja076298b] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yoko Nomura
- Department of Biomedical Engineering, University of California, Davis 451 East Health Sciences Drive, Davis, California 95616, USA
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Nomura Y, Yokobayashi Y. Dual selection of a genetic switch by a single selection marker. Biosystems 2007; 90:115-20. [PMID: 16942834 DOI: 10.1016/j.biosystems.2006.07.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2006] [Revised: 07/10/2006] [Accepted: 07/12/2006] [Indexed: 11/17/2022]
Abstract
Forward engineering of synthetic genetic circuits in living cells is expected to deliver various applications in biotechnology and medicine and to provide valuable insights into the design principles of natural gene networks. However, lack of biochemical data and complexity of biological environment complicate rational design of such circuits based on quantitative simulation. Previously, we have shown that directed evolution can complement our weakness in designing genetic circuits by screening or selecting functional circuits from a large pool of nonfunctional ones. Here we describe a dual selection strategy that allows selection of both ON and OFF states of genetic circuits using tetA as a single selection marker. We also describe a successful demonstration of a genetic switch selection from a 2000-fold excess background of nonfunctional switches in three rounds of iterative selection. The dual selection system is more robust than the previously reported selection system employing three genes, with no observed false positive mutants during the simulated selections.
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Affiliation(s)
- Yoko Nomura
- Department of Biomedical Engineering, University of California, Davis, 451 E. Health Sciences Dr., Davis, CA 95616, USA
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Jin J, Guffanti AA, Bechhofer DH, Krulwich TA. Tet(L) and tet(K) tetracycline-divalent metal/H+ antiporters: characterization of multiple catalytic modes and a mutagenesis approach to differences in their efflux substrate and coupling ion preferences. J Bacteriol 2002; 184:4722-32. [PMID: 12169596 PMCID: PMC135290 DOI: 10.1128/jb.184.17.4722-4732.2002] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Tet(L) protein encoded in the Bacillus subtilis chromosome and the closely related Tet(K) protein from Staphylococcus aureus plasmids are multifunctional antiporters that have three cytoplasmic efflux substrates: a tetracycline-divalent metal (TC-Me(2+)) complex that bears a net single positive charge, Na+, and K+. Tet(L) and Tet(K) had been shown to couple efflux of each of these substrates to influx of H+ as the coupling ion. In this study, competitive cross-inhibition between K+ and other cytoplasmic efflux substrates was demonstrated. Tet(L) and Tet(K) had also been shown to use K+ as an alternate coupling ion in support of Na+ or K+ efflux. Here they were shown to couple TC-Me(2+) efflux to K+ uptake as well, exhibiting greater use of K+ as a coupling ion as the external pH increased. The substrate and coupling ion preferences of the two Tet proteins differed, especially in the higher preference of Tet(K) than Tet(L) for K+, both as a cytoplasmic efflux substrate and as an external coupling ion. Site-directed mutagenesis was employed to test the hypothesis that some feature of the putative "antiporter motif," motif C, of Tet proteins would be involved in these characteristic preferences. Mutation of the A157 in Tet(L) to a hydroxyamino acid resulted in a more Tet(K)-like K+ preference both as coupling ion and efflux substrate. A reciprocal S157A mutant of Tet(K) exhibited reduced K+ preference. Competitive inhibition among substrates and the parallel effects of the single mutation upon K+ preference, as both an efflux substrate and coupling ion, are compatible with a model in which a single translocation pathway through the Tet(L) and Tet(K) transporters is used both for the cytoplasmic efflux substrates and for the coupling ions, in an alternating fashion. However, the effects of the A157 and other mutations of Tet(L) indicate that even if there are a shared binding site and translocation pathway, some elements of that pathway are used by all substrates and others are important only for particular substrates.
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Affiliation(s)
- Jie Jin
- Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, 1 Gustave L. Levy Place, New York, NY 10029, USA
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Stavropoulos TA, Strathdee CA. Synergy between tetA and rpsL provides high-stringency positive and negative selection in bacterial artificial chromosome vectors. Genomics 2001; 72:99-104. [PMID: 11247671 DOI: 10.1006/geno.2000.6481] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Bacterial artificial chromosome (bacmid) vectors are used to stably propagate large, complex fragments of cloned DNA and are a core technology for functional genomics. The simplest method of analyzing bacmid clones would involve a direct mutagenesis or allele exchange protocol utilizing positive and negative selectable markers. The utility of three different negative selectable markers to function in the context of a bacmid vector was therefore investigated: sacB from Bacillus subtilis, which confers sensitivity to sucrose; tetA from TN10, which confers resistance to tetracycline, osmotic sensitivity, and sensitivity to kanamycin and streptomycin; and rpsL from Escherichia coli, which confers sensitivity to streptomycin. When expressed individually in the context of a bacmid vector, each of these markers confers a similar stringency of negative selection, with plating efficiencies on selective media of 2.3 x 10(-5), 9.4 x 10(-4), and 5.7 x 10(-5), respectively. However coexpression of rpsL and tetA results in a synergistic enhancement of the osmotic, kanamycin, and streptomycin sensitivities, with a stringency of selection of approximately 50- to approximately 1000-fold over that obtained with rpsL or tetA alone and approximately 20-fold more than that obtained using sacB. The combination of rpsL and tetA thus serves as the most efficient positive and negative selectable marker system described to date.
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Affiliation(s)
- T A Stavropoulos
- Gene Therapy and Molecular Virology Group, The John P. Robarts Research Institute, London, Ontario, N6A 5K8, Canada
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11
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Stavropoulos TA, Strathdee CA. Expression of the tetA(C) tetracycline efflux pump in Escherichia coli confers osmotic sensitivity. FEMS Microbiol Lett 2000; 190:147-50. [PMID: 10981705 DOI: 10.1111/j.1574-6968.2000.tb09277.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Expression of tetA(C) in Escherichia coli confers resistance to tetracycline as well as sensitivity to nickel and cadmium salts, lipophilic chelating agents, and aminoglycoside antibiotics. In this report we determine that high-level expression of tetA(C) also confers an osmotic sensitivity. The osmotic-sensitive phenotype is distinct from the tetracycline-resistant phenotype and can be localized to a domain contained within the first 98 amino acid residues of the TetA(C) polypeptide.
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12
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Wang W, Guffanti AA, Wei Y, Ito M, Krulwich TA. Two types of Bacillus subtilis tetA(L) deletion strains reveal the physiological importance of TetA(L) in K(+) acquisition as well as in Na(+), alkali, and tetracycline resistance. J Bacteriol 2000; 182:2088-95. [PMID: 10735849 PMCID: PMC111255 DOI: 10.1128/jb.182.8.2088-2095.2000] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The chromosomally encoded TetA(L) protein of Bacillus subtilis is a multifunctional tetracycline-metal/H(+) antiporter that also exhibits monovalent cation/H(+) antiport activity and a net K(+) uptake mode. In this study, B. subtilis mutant strains JC112 and JC112C were found to be representative of two phenotypic types of tetA(L) deletion strains that are generated in the same selection. Both strains exhibited increased sensitivity to low tetracycline concentrations as expected. The mutants also had significantly reduced ability to grow in media containing low concentrations of K(+), indicating that the net K(+) uptake mode is of physiological consequence; the deficit in JC112 was greater than in JC112C. JC112 also exhibited (i) greater impairment of Na(+)- or K(+)-dependent growth at pH 8.3 than JC112C and (ii) a greater degree of Co(+2) as well as Na(+) sensitivity. Studies were initiated to explore the possibility of two different patterns of compensatory changes in other ion-translocating transporters in these mutants. Increased expression of two loci has thus far been shown. Increased expression of czcD-trkA, a locus with a proposed involvement in K(+) uptake, occurred in both mutants. The increase was highest in the presence of Co(2+) and was higher in JC112 than in JC112C. Deletion of czcD-trkA resulted in diminished growth of the wild-type and both mutant strains at low [K(+)], supporting a significant role for this locus in K(+) uptake. Expression of yheL, which is a homologue of the Na(+)/H(+) antiporter-encoding nhaC gene from Bacillus firmus OF4, was also increased in both tetA(L) deletion strains, again with higher up-regulation in JC112. The phenotypes resulting from deletion of yheL were consistent with a modest role for YheL in Na(+)-dependent pH homeostasis in the wild type. No major role for YheL was indicated in the mutants in spite of the overexpression. The studies underscore the multiple physiological functions of TetA(L), including tetracycline, Na(+), and alkali resistance and K(+) acquisition. The studies also reveal and begin to detail the complexity of the response to mutational loss of these functions.
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Affiliation(s)
- W Wang
- Department of Biochemistry and Molecular Biology, Mount Sinai School of Medicine, New York, New York 10029, USA
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Guffanti AA, Cheng J, Krulwich TA. Electrogenic antiport activities of the Gram-positive Tet proteins include a Na+(K+)/K+ mode that mediates net K+ uptake. J Biol Chem 1998; 273:26447-54. [PMID: 9756879 DOI: 10.1074/jbc.273.41.26447] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Two Gram-positive Tet proteins, TetA(L) from Bacillus subtilis and TetK from a Staphylococcus aureus plasmid, have previously been suggested to have multiple catalytic modes and roles. These include: tetracycline (Tc)-metal/H+ antiport for both proteins (Yamaguchi, A., Shiina, Y., Fujihira, E., Sawai, T., Noguchi, N., and Sasatsu, M. (1995) FEBS Lett. 365, 193-197; Cheng, J. Guffanti, A. A., Wang, W., Krulwich, T. A., and Bechhofer, D. H. (1996) J. Bacteriol. 178, 2853-2860); Na+(K+)/H+ antiport for both proteins (Cheng et al. (1996)); and an electrical potential-dependent K+ leak mode for TetK and highly truncated segments thereof that can facilitate net K+ uptake (Guay, G. G., Tuckman, M., McNicholas, P., and Rothstein, D. M. (1993) J. Bacteriol. 175, 4927-4929). Studies of membrane vesicles from Escherichia coli expressing low levels of complete and 3'-truncated versions of tetA(L) or tetK, now show that the full-length versions of both transporters catalyze electrogenic antiport and that demonstration of electrogenicity depends upon use of a low chloride buffer for the assay. The K+ uptake mode, assayed via 86Rb+ uptake, was also catalyzed by both full-length TetA(L) and TetK. This mode does not represent a potential-dependent leak. Such a leak was not demonstrable in energized membrane vesicles. Rather, Rb+ uptake occurred in right-side-out vesicles when the intravesicular space contained either Na+ or K+ but not choline. If an outwardly directed gradient of Na+ or K+ was present, Rb+ uptake occurred without energization in vesicles from cells transformed with a plasmid containing tetA(L) or tetK but not a control plasmid. Experiments in which a comparable exchange was carried out in low chloride buffers to which oxonol was added confirmed that the exchange was electrogenic. Thus, the K+ uptake mode is proposed to be a mode of the electrogenic monovalent cation/H+ antiport activity of TetA(L) and TetK in which K+ takes the place of the external protons. Truncated TetK and TetA(L) failed to catalyze either Tc-metal/H+ or Na+/H+ antiport in energized everted vesicles. Truncated TetK, but not TetA(L), did, however, exhibit modest, electrogenic Na+(K+)/Rb+ exchange as well as a small, potential-dependent leak of Rb+. The C-terminal halves of the TetA(L) and TetK proteins are thus required both for proton-coupled active transport activities of the multifunctional transporter and, perhaps, for minimizing cation leakiness.
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Affiliation(s)
- A A Guffanti
- Department of Biochemistry, Mount Sinai School of Medicine, New York, New York 10029, USA
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Cheng J, Guffanti AA, Wang W, Krulwich TA, Bechhofer DH. Chromosomal tetA(L) gene of Bacillus subtilis: regulation of expression and physiology of a tetA(L) deletion strain. J Bacteriol 1996; 178:2853-60. [PMID: 8631673 PMCID: PMC178020 DOI: 10.1128/jb.178.10.2853-2860.1996] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Deletion of the tetA(L) chromosomal region of Bacillus subtilis in a strain designated JC112 increased the strain's sensitivity to low tetracycline concentrations. It also resulted in phenotypic changes that correlate with the previously found role of TetA(L) in mediating electrogenic NA+/H+ antiport. Growth of JC112 was impaired relative to that of the wild type at both pH 7.0 and 8.3; Na(+)- and K(+)-dependent pH homeostases were impaired at alkaline pH. The phenotype of JC112 was complemented by plasmid-borne tetA(L) and related tet(K) genes; the antiport activity conferred by the tet(K) gene had an apparently higher preference for K+ over Na+ than that conferred by tetA(L). The data were consistent with TetA(L) being the major Na+(K+)/H+ antiporter involved in pH homeostasis in B. subtilis as well as a significant Na+ extrusion system. The phenotype of JC112 was much more pronounced than that of an earlier transposition mutant, JC111, with a disruption in the putative tetA(L) promoter region. Northern (RNA) blot analysis of tetA(L) RNA from wild-type and JC111 strains revealed the same patterns. That JC111 nevertheless exhibited some Na+ and alkali sensitivity may be accounted for by disruption of regulatory features that, in the wild type, allow increased tetA(L) expression under specific conditions of pH and monovalent cation concentration. Evidence for several different regulatory effects emerged from studies of lacZ expression from the transposon of JC111 and from a tetA(L)-lacZ translational fusion introduced into the amyE locus of wild-type and JC112 strains.
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Affiliation(s)
- J Cheng
- Department of Biochemistry, Mount Sinai School of Medicine, City University of New York, New York 10029, USA
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Cheng J, Baldwin K, Guffanti AA, Krulwich TA. Na+/H+ antiport activity conferred by Bacillus subtilis tetA(L), a 5' truncation product of tetA(L), and related plasmid genes upon Escherichia coli. Antimicrob Agents Chemother 1996; 40:852-7. [PMID: 8849239 PMCID: PMC163218 DOI: 10.1128/aac.40.4.852] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
An Escherichia coli transformant expressing the Bacillus subtilis tetA(L) gene from a weak promoter was challenged by growth on medium with low, increasing tetracycline concentrations. Changes in the substrate preference ratios of the TetA(L)-mediated resistances and antiports were examined in view of recent findings suggesting that TetA(L) catalyzes efflux of Na+ in exchange for protons in addition to having the ability to catalyze metal-tetracycline/H+ antiport. After growth of the transformant on 1 microgram or more of tetracycline per ml for 12 to 15 h, the tetA(L) gene in the plasmid was found to be disrupted by an IS10 element 50 bp from the 5' end of the coding sequence. This disrupted recombinant plasmid, pKB1, conferred greater tetracycline resistance and higher levels of membrane metal-tetracycline/proton antiport than the original plasmid, pJTA1, but conferred lower NA+ resistance and Na+/H+ antiport levels than the original plasmid. The results indicate that the 5' end of the gene is necessary for optimal Na+/H+ antiport but that some such activity as well as robust tetracycline/H+ antiport persists in its absence. Two plasmid genes, tet(K) and qacA, were compared with tetA(L) vis-à-vis their abilities to enhance the Na+/H+ antiporter activity of everted vesicles from E. coli transformants. tet(K), which is more closely related to tetA(L), catalyzed 22Na+ uptake by energized vesicles, whereas the less closely related qacA gene did not.
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Affiliation(s)
- J Cheng
- Department of Biochemistry, Mount Sinai School of Medicine, City University of New York, New York 10029, USA
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Chapter 6 Structure and function, of HlyB, the ABC-transporter essential for haemolysin secretion from escherichia coli. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s1383-8121(96)80047-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Varela MF, Sansom CE, Griffith JK. Mutational analysis and molecular modelling of an amino acid sequence motif conserved in antiporters but not symporters in a transporter superfamily. Mol Membr Biol 1995; 12:313-9. [PMID: 8747276 DOI: 10.3109/09687689509072433] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Elements of a 'G X8 G X3 G P X2 G G' amino acid sequence motif were conserved in the fifth predicted membrane-spanning domains of 31 antiporters, but none of 27 symporters or uniporters that together comprise a 'superfamily' of structurally, related transport proteins. Molecular modelling and mechanics predicted that the GP dipeptide of this motif bends the antiporters' fifth transmembrane helices, and that the repeating pattern of glycine residues forms a pocket, devoid of side chains, on the surface of these helices. The glycine residue in the motif's GP dipeptide was conserved in 90% of these antiporters with alanine being the only observed substitution. Replacement of the glycine residue of the GP dipeptide with alanine and serine reduced the level of tetracycline resistance conferred by TetA(C), a tetracycline/H+ antiporter, by 74 and 81%, respectively. All other substitutions totally abolished resistance to tetracycline. In contrast, replacement of the glycine residue of the GP dipeptide did not abolish increased susceptibility to cadmium, another phenotype conferred by TetA(C) independent of resistance to tetracycline. These results suggest that the glycine of the GP dipeptide is necessary for the tetracycline/H+ antiport activity of TetA(C), rather than its expression, stability, or general three-dimensional structure.
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Affiliation(s)
- M F Varela
- Department of Biochemistry, University of New Mexico School of Medicine, Albuquerque 87131, USA
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Guffanti AA, Krulwich TA. Tetracycline/H+ antiport and Na+/H+ antiport catalyzed by the Bacillus subtilis TetA(L) transporter expressed in Escherichia coli. J Bacteriol 1995; 177:4557-61. [PMID: 7635843 PMCID: PMC177215 DOI: 10.1128/jb.177.15.4557-4561.1995] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The properties of TetA(L)-dependent tetracycline/proton and Na+/proton antiport were studied in energized everted vesicles of Escherichia coli transformed with a cloned tetA(L) gene (pJTA1) from Bacillus subtilis. Inhibition patterns by valinomycin and nigericin indicated that both antiports were electrogenic, in contrast to the tetracycline/proton antiport encoded by gram-negative plasmid tet genes. Tetracycline uptake in the everted system was dependent upon a divalent cation, with cobalt being the preferred one. The apparent Km for tetracycline was markedly increased at pH 8.5 versus pH 7.5, whereas the Vmax was unchanged. The much higher apparent Km for Na+ decreased at pH 8.5 relative to that at pH 7.5, as did the Vmax. Na+ did not affect tetracycline uptake, nor did Co2+ and/or tetracycline affect Na+ uptake; complex patterns of inhibition by amiloride and analogs thereof were observed.
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Affiliation(s)
- A A Guffanti
- Department of Biochemistry, Mount Sinai School of Medicine of CUNY, New York 10029, USA
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