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Baym M, Stone LK, Kishony R. Multidrug evolutionary strategies to reverse antibiotic resistance. Science 2016; 351:aad3292. [PMID: 26722002 DOI: 10.1126/science.aad3292] [Citation(s) in RCA: 409] [Impact Index Per Article: 51.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Antibiotic treatment has two conflicting effects: the desired, immediate effect of inhibiting bacterial growth and the undesired, long-term effect of promoting the evolution of resistance. Although these contrasting outcomes seem inextricably linked, recent work has revealed several ways by which antibiotics can be combined to inhibit bacterial growth while, counterintuitively, selecting against resistant mutants. Decoupling treatment efficacy from the risk of resistance can be achieved by exploiting specific interactions between drugs, and the ways in which resistance mutations to a given drug can modulate these interactions or increase the sensitivity of the bacteria to other compounds. Although their practical application requires much further development and validation, and relies on advances in genomic diagnostics, these discoveries suggest novel paradigms that may restrict or even reverse the evolution of resistance.
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Affiliation(s)
- Michael Baym
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA
| | - Laura K Stone
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA
| | - Roy Kishony
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA. Department of Biology and Department of Computer Science, Technion - Israel Institute of Technology, Haifa, Israel.
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2
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Fried L, Lassak J, Jung K. A comprehensive toolbox for the rapid construction of lacZ fusion reporters. J Microbiol Methods 2012; 91:537-43. [PMID: 23022912 DOI: 10.1016/j.mimet.2012.09.023] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 09/19/2012] [Accepted: 09/19/2012] [Indexed: 12/19/2022]
Abstract
β-Galactosidase encoded by lacZ remains a popular reporter enzyme. Here, we present three fast and convenient tools that facilitate rapid construction of reporter lacZ fusions. The first enables the simple generation of lacZ (slacZ)-based chromosomally encoded reporter fusions within the lac operon in Escherichia coli using Red®/ET® recombination. The slacZ tool is based on rpsL counter-selection in combination with homologous recombination catalyzed by the λ Red recombinase, and blue/white screening. This permits construction of transcriptional and translational reporter lacZ fusions within a day. The second tool allows the introduction of lacZ reporter fusions into the chromosome by a single-crossover method. The strategy relies on the γ-origin-based suicide vector pNPTS138-R6KT, which can only replicate in λpir E. coli strains. The third tool comprises four pBBR1-based broad-host-range vectors for transcriptional and translational lacZ fusions. The functionality of our toolbox was confirmed by the K(+)-dependent activation of kdp promoter-lacZ fusions in vivo.
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Affiliation(s)
- Luitpold Fried
- Munich Center for Integrated Protein Science (CIPSM) at the Department of Microbiology, Ludwig-Maximilians-Universität München, 82152 Martinsried, Germany
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3
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Abromaitis S, Faucher S, Béland M, Curtiss R, Daigle F. The presence of thetetgene from cloning vectors impairsSalmonellasurvival in macrophages. FEMS Microbiol Lett 2005; 242:305-12. [PMID: 15621452 DOI: 10.1016/j.femsle.2004.11.024] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2004] [Accepted: 11/09/2004] [Indexed: 11/16/2022] Open
Abstract
Cloning, mutagenesis and complementation of virulence factors are key steps to understand the mechanisms of bacterial pathogenesis and cloning vectors are routinely utilized for these processes. We have investigated the effect of the presence of commonly used cloning vectors on the survival of the intracellular bacterial pathogen Salmonella during macrophage infection. We demonstrate that the presence of the pSC101 derived tetracycline resistance gene on plasmids causes a lower survival rate of Salmonella in macrophages. The decrease in survival caused by the presence of the tet gene was not due to a higher susceptibility to gentamicin, a growth defect, or to increased sensitivity to acid. Higher susceptibility to hydrogen peroxide was observed in vitro for strain containing plasmid with the tet gene when the strains were grown at high densities but not when they were grown at low densities. Our findings demonstrate that the use of the tet gene for mutation or complementation can have deleterious effects and should thus be carefully considered.
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4
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Sardesai AA, Gowrishankar J. Improvement in K+-limited growth rate associated with expression of the N-terminal fragment of one subunit (KdpA) of the multisubunit Kdp transporter in Escherichia coli. J Bacteriol 2001; 183:3515-20. [PMID: 11344160 PMCID: PMC99650 DOI: 10.1128/jb.183.11.3515-3520.2001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mutations in any one of three genes, kdpA, -B, or -C, in Escherichia coli abolish the activity of Kdp, a multisubunit K+-ATPase that belongs to the P-type ATPase family of cation transporters. We found in this study that expression in vivo of a 135-amino-acid-long N-terminal fragment (KdpA'), less than one-quarter the length of native KdpA, was able to mediate an improvement in K+-limited growth rates in two different contexts, even in the absence of both KdpC and the ATPase subunit KdpB. The first context was when KdpA' was overexpressed in cells from a heterologous inducible promoter, and the second was when KdpA' was provided with a C-terminally altered extension (following a spontaneous genetic rearrangement). Our results suggest that KdpA' provides an incipient pathway for K+ translocation which can serve to transport K+ into the cells in response to the cytoplasmic membrane potential.
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Affiliation(s)
- A A Sardesai
- Centre for Cellular and Molecular Biology, Hyderabad 500 007, India
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5
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Jin J, Guffanti AA, Beck C, Krulwich TA. Twelve-transmembrane-segment (TMS) version (DeltaTMS VII-VIII) of the 14-TMS Tet(L) antibiotic resistance protein retains monovalent cation transport modes but lacks tetracycline efflux capacity. J Bacteriol 2001; 183:2667-71. [PMID: 11274128 PMCID: PMC95185 DOI: 10.1128/jb.183.8.2667-2671.2001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A "Tet(L)-12" version of Tet(L), a tetracycline efflux protein with 14 transmembrane segments (TMS), was constructed by deletion of two central TMS. Tet(L)-12 catalyzed Na+/H+ antiport and antiport with K+ as a coupling ion as well as or better than wild-type Tet(L) but exhibited no tetracycline-Me2+/H+ antiport in Escherichia coli vesicles.
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Affiliation(s)
- J Jin
- Department of Biochemistry and Molecular Biology, Mount Sinai School of Medicine, New York, New York 10029, USA
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6
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Saraceni-Richards CA, Levy SB. Evidence for interactions between helices 5 and 8 and a role for the interdomain loop in tetracycline resistance mediated by hybrid Tet proteins. J Biol Chem 2000; 275:6101-6. [PMID: 10692399 DOI: 10.1074/jbc.275.9.6101] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
An interdomain hybrid Tet protein consisting of a class C alpha domain and a class B beta domain (Tet(C/B)) lacks detectable efflux ability and provides only minimal levels of resistance to tetracycline (Tc) (3 microg/ml) compared with intact class B (256 microg/ml) and class C (64 microg/ml). Twenty-one independently isolated mutants of the Tet(C/B) protein with increased Tc resistance were generated by random chemical mutagenesis. Nine mutants with a Glu substitution for Gly-152 in helix 5 of the class C alpha domain produced a resistance of 48 microg/ml, whereas another 9 with an Asp replacement of Gly-247 in helix 8 of the class B beta domain mediated resistance at 32 microg/ml. The third type of mutation, found in 3 mutants expressing 24 microg/ml resistance, was a S202F replacement in the putative interdomain cytoplasmic loop of Tet(C/B). The latter underscores a previously unappreciated function of the interdomain cytoplasmic loop. All three types of Tet(C/B) mutant proteins were expressed in amounts comparable with that of the original protein and demonstrated restored energy-dependent efflux of tetracycline. Site-directed mutational analysis demonstrated that a Gly-247 to Asn mutation could also facilitate Tc resistance by the Tet(C/B) hybrid, and a negatively charged side chain at position 152 was required for Tet(C/B) activity. These mutations appear to promote the necessary functional interactions between the interclass domains that do not occur in the Tet(C/B) hybrid protein and suggest a direct association between helix 5 and helix 8 in the function of Tet efflux proteins.
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Affiliation(s)
- C A Saraceni-Richards
- Center for Adaptation Genetics and Drug Resistance and Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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7
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Ginn SL, Brown MH, Skurray RA. The TetA(K) tetracycline/H(+) antiporter from Staphylococcus aureus: mutagenesis and functional analysis of motif C. J Bacteriol 2000; 182:1492-8. [PMID: 10692352 PMCID: PMC94444 DOI: 10.1128/jb.182.6.1492-1498.2000] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Conserved motif C, identified within members of the major facilitator superfamily (MFS) of transport proteins that mediate drug export, was examined in the tetracycline resistance efflux protein TetA(K) from Staphylococcus aureus; motif C is contained within transmembrane segment 5. Using site-directed mutagenesis, the importance of the conserved glycine (G151, G155, G159, and G160) and proline (P156) residues within this motif was investigated. Over 40 individual amino acid replacements were introduced; however, only alanine and serine substitutions for glycine at G151, G155, and G160 were found to retain significant levels of tetracycline resistance and transport activity in cells expressing mutant proteins. Notably, P156 and G159 appear to be crucial, as amino acid replacements at these positions either significantly reduced or abolished tetracycline/H(+) activity. The highly conserved nature of motif C and its distribution throughout drug exporters imply that the residues of motif C play a similar role in all MFS proteins that function as antiporters.
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Affiliation(s)
- S L Ginn
- School of Biological Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
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8
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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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9
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Daugelavicius R, Bamford JK, Grahn AM, Lanka E, Bamford DH. The IncP plasmid-encoded cell envelope-associated DNA transfer complex increases cell permeability. J Bacteriol 1997; 179:5195-202. [PMID: 9260964 PMCID: PMC179380 DOI: 10.1128/jb.179.16.5195-5202.1997] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
IncP-type plasmids are broad-host-range conjugative plasmids. DNA translocation requires DNA transfer-replication functions and additional factors required for mating pair formation (Mpf). The Mpf system is located in the cell membranes and is responsible for DNA transport from the donor to the recipient. The Mpf complex acts as a receptor for IncP-specific phages such as PRD1. In this investigation, we quantify the Mpf complexes on the cell surface by a phage receptor saturation technique. Electrochemical measurements are used to show that the Mpf complex increases cell envelope permeability to lipophilic compounds and ATP. In addition it reduces the ability of the cells to accumulate K+. However, the Mpf complex does not dissipate the membrane voltage. The Mpf complex is rapidly disassembled when intracellular ATP concentration is decreased, as measured by a PRD1 adsorption assay.
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Affiliation(s)
- R Daugelavicius
- Department of Biosciences, Biocenter, University of Helsinki, Finland
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10
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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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11
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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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12
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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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13
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Nakamura T, Matsuba Y, Yamamuro N, Booth IR, Unemoto T. Cloning and sequencing of a K+ transport gene (trk A) from the marine bacterium Vibrio alginolyticus. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1219:701-5. [PMID: 7948029 DOI: 10.1016/0167-4781(94)90231-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A gene has been cloned from the marine bacterium Vibrio alginolyticus that functionally complements a mutant strain of Escherichia coli, TK420, defective in K+ transport genes (kdpABC, trkD, trkA). The cloned Vibrio gene allowed TK420 to grow in a synthetic medium containing less than 10 mM K+ and concomitantly led to an increase in K+ uptake activity. The nucleotide sequence of the cloned fragment revealed an open reading frame, which encodes a protein with a predicted 458 amino acid sequence and molecular mass of 50,122 Da. This gene has 71% homology to trkA gene at the DNA level from E. coli and the deduced amino acid sequence is 79% identical with E. coli TrkA, implying that V. alginolyticus has a trkA-like gene as a component of K+ transport systems.
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Affiliation(s)
- T Nakamura
- Laboratory of Membrane Biochemistry, Faculty of Pharmaceutical Sciences, Chiba University, Japan
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14
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Cheng J, Guffanti AA, Krulwich TA. The chromosomal tetracycline resistance locus of Bacillus subtilis encodes a Na+/H+ antiporter that is physiologically important at elevated pH. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)46994-3] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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15
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Griffith JK, Cuellar DH, Fordyce CA, Hutchings KG, Mondragon AA. Structure and function of the class C tetracycline/H+ antiporter: three independent groups of phenotypes are conferred by TetA (C). Mol Membr Biol 1994; 11:271-7. [PMID: 7711837 DOI: 10.3109/09687689409160437] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The class C tetracycline/H+ antiporter, TetA(C), confers nine distinct phenotypes in Escherichia coli: resistance to tetracycline, reduced culture density at stationary phase (growth yield), increased supercoiling of plasmid DNA, delayed growth in succinate minimal medium, complementation of potassium uptake defects, increased susceptibility to cadmium, increased susceptibility to fusaric acid, increased susceptibility to bleomycin and increased susceptibility to several classes of cationic aminoglycoside antibiotics. These nine phenotypes were resolved into three 'linkage' groups based on their patterns of suppression by mutations of the tetA(C) gene of plasmid pBR322. Group I includes resistance to tetracycline, increased susceptibility to cadmium and reduced growth yield. Group II includes delayed growth in succinate minimal medium and complementation of potassium uptake defects. Group III includes increased supercoiling of plasmid DNA and increased susceptibilities to fusaric acid, bleomycin and cationic aminoglycosides. Phenotypes of Groups II and III, but not Group I, also were conferred by a chimeric gene encoding a fusion between the N-terminal 34 residues of TetA(C) and the C-terminal 429 residues of a structurally-similar protein, the E. coli galactose/H+ symporter, GalP. In contrast, none of these phenotypes was conferred by a chimeric gene encoding a fusion between the N-terminal 34 residues of TetA(C) and a structurally-dissimilar protein, TEM beta-lactamase. These results demonstrate that the three groups of linked phenotypes are dependent on different elements of the TetA(C) amino acid sequence, implying that TetA(C) confers these phenotypes by at least three independent mechanisms.
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Affiliation(s)
- J K Griffith
- Department of Cell Biology, University of New Mexico School of Medicine, Albuquerque 87131
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16
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Guay GG, Tuckman M, McNicholas P, Rothstein DM. The tet(K) gene from Staphylococcus aureus mediates the transport of potassium in Escherichia coli. J Bacteriol 1993; 175:4927-9. [PMID: 8335648 PMCID: PMC204949 DOI: 10.1128/jb.175.15.4927-4929.1993] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The tet(K) gene, encoding the tetracycline efflux protein from Staphylococcus aureus, mediates the transport of potassium in an Escherichia coli mutant defective in potassium uptake. Deletion mapping indicates that the first third of the tet(K) gene is sufficient to mediate potassium transport.
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Affiliation(s)
- G G Guay
- Department of Microbial Genetics and Biochemistry, Lederle Laboratories, Pearl River, New York 10965
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17
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Varela MF, Griffith JK. Nucleotide and deduced protein sequences of the class D tetracycline resistance determinant: relationship to other antimicrobial transport proteins. Antimicrob Agents Chemother 1993; 37:1253-8. [PMID: 7916584 PMCID: PMC187949 DOI: 10.1128/aac.37.6.1253] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The nucleotide sequence of the plasmid pRA1 gene encoding the TetA(D) tetracycline/H+ antiporter was determined. The deduced amino acid sequence was compared with those of other antimicrobial and antiseptic transporters. The deduced product of tetA(D) is a 41.1-kDa protein consisting of 394 amino acids comprising 12 membrane-spanning domains. Three classes of amino acid motifs found in TetA(D) are highly conserved in other transporters, implying that they participate in structures necessary for substrate recognition, binding, or translocation. A common mechanism of transport is suggested, with subtle sequence variations accounting for varied substrate specificities, modes of transport, and directions of transport.
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Affiliation(s)
- M F Varela
- Department of Cell Biology, School of Medicine, University of New Mexico, Albuquerque 87131
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18
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Lynch AS, Wang JC. Anchoring of DNA to the bacterial cytoplasmic membrane through cotranscriptional synthesis of polypeptides encoding membrane proteins or proteins for export: a mechanism of plasmid hypernegative supercoiling in mutants deficient in DNA topoisomerase I. J Bacteriol 1993; 175:1645-55. [PMID: 8383663 PMCID: PMC203958 DOI: 10.1128/jb.175.6.1645-1655.1993] [Citation(s) in RCA: 133] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
A homologous set of plasmids expressing tet, lacY, and melB, genes encoding integral cytoplasmic membrane proteins, and tolC and ampC, genes encoding proteins for export through the cytoplasmic membrane, was constructed for studying the effects of transcription and translation of such genes on the hypernegative supercoiling of plasmids in Escherichia coli cells deficient in DNA topoisomerase I. The results support the view that intracellular bacterial DNA is anchored to the cytoplasmic membrane at many points through cotranscriptional synthesis of membrane proteins or proteins designated for export across the cytoplasmic membrane; in the latter case, the presence of the signal peptide appears to be unnecessary for cotranscriptional membrane association.
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Affiliation(s)
- A S Lynch
- Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, Massachusetts 02138
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19
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Abstract
The TetA(C) protein, encoded by the tetA(C) gene of plasmid pBR322, is a member of a family of membrane-bound proteins that mediate energy-dependent efflux of tetracycline from the bacterial cell. The tetA(C) gene was mutagenized with hydroxylamine, and missense mutations causing the loss of tetracycline resistance were identified at 30 distinct codons. Mutations that encoded substitutions within putative membrane-spanning alpha-helical regions were scattered throughout the gene. In contrast, mutations outside the alpha-helical regions were clustered in two cytoplasmic loops, between helices 2 and 3 and helices 10 and 11, suggesting that these regions play a critical role in the recognition of tetracycline and/or energy transduction. All of the missense mutations encoded a protein that retained the ability to rescue an Escherichia coli strain defective in potassium uptake, suggesting that the loss of tetracycline resistance was not due to an unstable TetA(C) protein or to the failure of the protein to be inserted in the membrane. We postulate that the mutations encode residues that are critical for the active efflux of tetracycline, except for mutations that result in the introduction of charged residues within hydrophobic regions of the TetA(C) protein.
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Affiliation(s)
- P McNicholas
- Department of Microbial Genetics, Lederle Laboratories, Pearl River, New York 10965
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20
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Thomas WD, Wagner SP, Welch RA. A heterologous membrane protein domain fused to the C-terminal ATP-binding domain of HlyB can export Escherichia coli hemolysin. J Bacteriol 1992; 174:6771-9. [PMID: 1400227 PMCID: PMC207352 DOI: 10.1128/jb.174.21.6771-6779.1992] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The hydrophobic-rich NH2-terminal 34 amino acids of a tetracycline resistance determinant (TetC) were fused to the COOH-terminal 240 amino acids of the hemolysin transporter, HlyB, which contains a putative ATP-binding domain. This hybrid protein replaced the NH2-terminal 467-amino-acid portion of HlyB and could still export the Escherichia coli hemolysin (HlyA). Export by the hybrid protein was approximately 10% as efficient as transport by HlyB. Extracellular secretion of HlyA by the TetC-HlyB hybrid required HlyD and TolC. The extracellular and periplasmic levels of beta-galactosidase and beta-lactamase in strains that produced the hybrid were similar to the levels in controls. Thus, HlyA transport was specific and did not appear to be due to leakage of cytoplasmic contents alone. Antibodies raised against the COOH terminus of HlyB reacted with the hybrid protein, as well as HlyB. HlyB was associated with membrane fractions, while the hybrid protein was found mainly in soluble extracts. Cellular fractionation studies were performed to determine whether transport by the hybrid occurred simultaneously across both membranes like wild-type HlyA secretion. However, we found that HlyA was present in the periplasm of strains that expressed the TetC-HlyB hybrid. HlyA remained in the periplasm unless the hlyD and tolC gene products were present in addition to the hybrid.
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Affiliation(s)
- W D Thomas
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison 53706
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21
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Rosner JL, Aumercier M. Potentiation by salicylate and salicyl alcohol of cadmium toxicity and accumulation in Escherichia coli. Antimicrob Agents Chemother 1990; 34:2402-6. [PMID: 2088194 PMCID: PMC172069 DOI: 10.1128/aac.34.12.2402] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The toxicity of Cd2+ in Escherichia coli K-12 was potentiated by salicylate and several related compounds. The efficiency of plating on Luria broth plates was reduced by more than 10(5)-fold when 10 mM salicylate and 200 microM CdCl2 were present simultaneously but was unaffected when either compound was present by itself. Synergistic effects were found at pH 7.4 with certain other weak acids (acetyl salicylate [aspirin], benzoate, and cinnamate) and with a nonacidic salicylate analog, salicyl alcohol, but not with acetate or p-hydroxy benzoate. Thus, the synergism with Cd2+ is determined by the structure of the compounds and not merely by their acidity. The kinetics of 109Cd2+ uptake by cells grown and assayed in broth indicated the presence of two uptake systems with Kms of 1 and 52 microM Cd2+ and Vmaxs of 0.059 and 1.5 mumol of Cd2+ per min per g of cells, respectively. The kinetics of uptake for cells grown and assayed with 20 mM salicyl alcohol showed 2.5-fold increases in the Vmaxs of both systems but no change in the Kms. Salicylate-grown cells also exhibited increased rates of 109Cd2+ uptake by both systems. Thus, enhanced uptake of Cd2+ may be responsible for the potentiation of Cd2+ toxicity by salicylate and salicyl alcohol.
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Affiliation(s)
- J L Rosner
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892
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22
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Wyka MA, St John AC. Effects of production of abnormal proteins on the rate of killing of Escherichia coli by streptomycin. Antimicrob Agents Chemother 1990; 34:534-8. [PMID: 2188585 PMCID: PMC171639 DOI: 10.1128/aac.34.4.534] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The role of abnormal membrane proteins in modulating the rate of killing by streptomycin was investigated. Davis et al. (B.D. Davis, L. Chen, and P.T. Tai, Proc. Natl. Acad. Sci. USA 83:6164-6168, 1986) have proposed that misread membrane proteins created by the action of streptomycin on translating ribosomes cause the formation of nonspecific membrane channels which allow increased uptake of the antibiotic and contribute to its bactericidal action. Pretreatment of Escherichia coli with a low concentration of puromycin enhanced the rate of killing by streptomycin. The effect of the pretreatment with puromycin was transient, since approximately normal rates of killing by streptomycin were restored after 30 min of incubation in antibiotic-free medium. This time period correlates with the time required to degrade labile polypeptides in puromycin-treated cells. The induction of a specific abnormal malE-lacZ fusion protein, which is capable of disrupting the normal membrane protein secretion process, also increased the rate of killing by streptomycin. Induction of malF-phoA fusion proteins, which have no significant effects on membrane integrity, did not alter susceptibility to streptomycin. These observations suggest that certain abnormal membrane proteins can contribute to the bactericidal action of streptomycin.
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Affiliation(s)
- M A Wyka
- Department of Biological Sciences, Nelson Biological Laboratories, Rutgers University, Piscataway, New Jersey 08855-1059
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23
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Schatz PJ, Riggs PD, Jacq A, Fath MJ, Beckwith J. The secE gene encodes an integral membrane protein required for protein export in Escherichia coli. Genes Dev 1989; 3:1035-44. [PMID: 2673920 DOI: 10.1101/gad.3.7.1035] [Citation(s) in RCA: 136] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Genetic screening and selection procedures employing a secA-lacZ fusion strain repeatedly have yielded mutations in four genes affecting the protein export pathway of Escherichia coli. These genes are secA, secD, prlA/secY, and secE. We discuss the significance of the failure to find new sec genes after extensive use of this approach. One of the genes, secE, has been characterized in some detail. From the DNA sequence of the gene and analysis of alkaline phosphatase fusions to the SecE protein, we propose that it is a 13,600-dalton integral cytoplasmic membrane protein. The data presented here and in the accompanying paper strongly suggest that secE has an important role in E. coli protein export.
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Affiliation(s)
- P J Schatz
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115
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24
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Abstract
Twin domains of positive and negative supercoiling are thought to form in DNA molecules whenever free rotation of a transcription complex around the DNA helix is impeded. Evidence for these domains has come from findings with Escherichia coli strains that are deficient in DNA topoisomerase I (top mutants) or that have been treated with DNA gyrase inhibitors. Plasmid pBR322 is highly supercoiled in these strains, whereas some of its deletion derivatives are not. The studies of pBR322 derivatives presented here show that high negative supercoiling in top strains requires translation as well as transcription of the first 98 codons of the tet gene and does not require the divergently transcribed amp gene. The N-terminal region of the TetA protein is thought to insert into the inner membrane. Our results favor models in which supercoiling domains are created when DNA segments are anchored to a large cellular structure via coupled transcription, translation, and membrane insertion of a nascent protein.
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Affiliation(s)
- J K Lodge
- Department of Microbiology and Immunology, Washington University Medical School, St. Louis, Missouri 63110
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25
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Merlin TL, Corvo DL, Gill JH, Griffith JK. Enhanced gentamicin killing of Escherichia coli by tet gene expression. Antimicrob Agents Chemother 1989; 33:230-2. [PMID: 2655531 PMCID: PMC171462 DOI: 10.1128/aac.33.2.230] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Time-kill studies were performed to determine the effect of tetracycline resistance (tet) gene expression on gentamicin killing of Escherichia coli. Expression of tet increased gentamicin killing in laboratory strains and clinical isolates. A role for tetracycline in inducing tet expression and increasing the bactericidal activity of aminoglycosides is suggested.
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Affiliation(s)
- T L Merlin
- Laboratory Service, Albuquerque Veterans Administration Medical Center, New Mexico 87108
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