# | Rank | Similarity | Title + Abs. | Year | PMID |
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 |
| 352 | 0 | 0.9949 | Transposon vectors containing non-antibiotic resistance selection markers for cloning and stable chromosomal insertion of foreign genes in gram-negative bacteria. A simple procedure for cloning and stable insertion of foreign genes into the chromosomes of gram-negative eubacteria was developed by combining in two sets of plasmids (i) the transposition features of Tn10 and Tn5; (ii) the resistances to the herbicide bialaphos, to mercuric salts and organomercurial compounds, and to arsenite, and (iii) the suicide delivery properties of the R6K-based plasmid pGP704. The resulting constructions contained unique NotI or SfiI sites internal to either the Tn10 or the Tn5 inverted repeats. These sites were readily used for cloning DNA fragments with the help of two additional specialized cloning plasmids, pUC18Not and pUC18Sfi. The newly derived constructions could be maintained only in donor host strains that produce the R6K-specified pi protein, which is an essential replication protein for R6K and plasmids derived therefrom. Donor plasmids containing hybrid transposons were transformed into a specialized lambda pir lysogenic Escherichia coli strain with a chromosomally integrated RP4 that provided broad-host-range conjugal transfer functions. Delivery of the donor plasmids into selected host bacteria was accomplished through mating with the target strain. Transposition of the hybrid transposon from the delivered suicide plasmid to a replicon in the target cell was mediated by the cognate transposase encoded on the plasmid at a site external to the transposon. Since the transposase function was not maintained in target cells, such cells were not immune to further transposition rounds. Multiple insertions in the same strain are therefore only limited by the availability of distinct selection markers. The utility of the system was demonstrated with a kanamycin resistance gene as a model foreign insert into Pseudomonas putida and a melanin gene from Streptomyces antibioticus into Klebsiella pneumoniae. Because of the modular nature of the functional parts of the cloning vectors, they can be easily modified and further selection markers can be incorporated. The cloning system described here will be particularly useful for the construction of hybrid bacteria that stably maintain inserted genes, perhaps in competitive situations (e.g., in open systems and natural environments), and that do not carry antibiotic resistance markers characteristic of most available cloning vectors (as is currently required of live bacterial vaccines). | 1990 | 2172216 |
| 389 | 1 | 0.9948 | Implantation of unmarked regulatory and metabolic modules in Gram-negative bacteria with specialised mini-transposon delivery vectors. Engineering of robust and safe microbial cell factories requires genetic tools somewhat different from those traditionally used for laboratory-adapted microorganisms. We took advantage of the properties of broad-host-range mini-Tn5 vectors and two regulated expression systems (LacI(Q)/P(trc) and XylS/Pm), together with FRT-flanked, excisable antibiotic resistance determinants, to generate a set of vectors for the delivery of gene(s) into the chromosome of Gram-negative bacteria. This arrangement of modular elements allows the cloning and subsequent markerless insertion of expression cargoes and leaves behind an antibiotic-sensitive host upon the action of the yeast Flp recombinase. We engineered a Pseudomonas putida KT2440 Pm::gfp strain that displayed strong fluorescence upon exposure to 3-methylbenzoate, a XylS effector, and allowed us to examine the performance of the Pm promoter at the single cell level. We also reconstructed a device for sugar transport and phosphorylation in Escherichia coli independent of the native phosphoenolpyruvate-dependent phosphotransferase system by the stable implantation of genes derived from the obligate anaerobe Zymomonas mobilis. In both cases, the information carried by the implanted genes was stably inherited in the absence of any selective pressure. Deliverable expression systems such as those described here will enhance the applicability of various Gram-negative bacteria in biocatalysis and environmental bioremediation. | 2013 | 22609234 |
| 349 | 2 | 0.9946 | Mini-Tn5 transposon derivatives for insertion mutagenesis, promoter probing, and chromosomal insertion of cloned DNA in gram-negative eubacteria. A collection of Tn5-derived minitransposons has been constructed that simplifies substantially the generation of insertion mutants, in vivo fusions with reporter genes, and the introduction of foreign DNA fragments into the chromosome of a variety of gram-negative bacteria, including the enteric bacteria and typical soil bacteria like Pseudomonas species. The minitransposons consist of genes specifying resistance to kanamycin, chloramphenicol, streptomycin-spectinomycin, and tetracycline as selection markers and a unique NotI cloning site flanked by 19-base-pair terminal repeat sequences of Tn5. Further derivatives also contain lacZ, phoA, luxAB, or xylE genes devoid of their native promoters located next to the terminal repeats in an orientation that affords the generation of gene-operon fusions. The transposons are located on a R6K-based suicide delivery plasmid that provides the IS50R transposase tnp gene in cis but external to the mobile element and whose conjugal transfer to recipients is mediated by RP4 mobilization functions in the donor. | 1990 | 2172217 |
| 390 | 3 | 0.9945 | A new simple method for introducing an unmarked mutation into a large gene of non-competent Gram-negative bacteria by FLP/FRT recombination. BACKGROUND: For the disruption of a target gene in molecular microbiology, unmarked mutagenesis is preferable to marked mutagenesis because the former method raises no concern about the polar effect and leaves no selection marker. In contrast to naturally competent bacteria, there is no useful method for introducing an unmarked mutation into a large gene of non-competent bacteria. Nevertheless, large genes encoding huge proteins exist in diverse bacteria and are interesting and important for physiology and potential applications. Here we present a new method for introducing an unmarked mutation into such large genes of non-competent Gram-negative bacteria. RESULTS: Two gene replacement plasmids, pJQFRT and pKFRT/FLP, were constructed to apply the FLP/FRT recombination system to introduce an unmarked mutation into a large gene of non-competent Gram-negative bacteria. In our methodology, pJQFRT and pKFRT/FLP are integrated into the upstream and the downstream regions of a target gene, respectively, through homologous recombination. The resultant mutant has antibiotic resistance markers, the sacB counter-selection marker, flp recombinase under the control of the tetR regulator, and identical FRT sites sandwiching the target gene and the markers on its chromosome. By inducing the expression of flp recombinase, the target gene is completely deleted together with the other genes derived from the integrated plasmids, resulting in the generation of an unmarked mutation. By this method, we constructed an unmarked mutant of ataA, which encodes the huge trimeric autotransporter adhesin (3,630 aa), in a non-competent Gram-negative bacterium, Acinetobacter sp. Tol 5. The unmarked ataA mutant showed the same growth rate as wild type Tol 5, but lost the adhesive properties of Tol 5, similar to the transposon-inserted mutant of ataA that we generated previously. CONCLUSIONS: The feasibility of our methodology was evidenced by the construction of an unmarked ataA mutant in the Tol 5 strain. Since FLP/FRT recombination can excise a long region of DNA exceeding 100 kb, our method has the potential to selectively disrupt much larger genes or longer regions of gene clusters than ataA. Our methodology allows the straightforward and efficient introduction of an unmarked mutation into a large gene or gene cluster of non-enterobacterial Gram-negative bacteria. | 2013 | 23594401 |
| 381 | 4 | 0.9945 | A panel of Tn7-based vectors for insertion of the gfp marker gene or for delivery of cloned DNA into Gram-negative bacteria at a neutral chromosomal site. The use of Tn7-based systems for site-specific insertion of DNA into the chromosome of Gram-negative bacteria has been limited due to the lack of appropriate vectors. We therefore developed a flexible panel of Tn7 delivery vectors. In one group of vectors, the miniTn7 element, which is inserted into the chromosome, contains a multiple cloning site (MCS) and the kanamycin, streptomycin or gentamicin resistance markers. Another group of vectors intended for tagging with green fluorescent protein (GFP) carries the gfpmut3* gene controlled by the modified lac promoter PA1/04/03, several transcriptional terminators, and various resistance markers. These vectors insert Tn7 into a specific, neutral intergenic region immediately downstream of the gene encoding glucosamine-6-phosphate synthetase (GlmS) in the tested fluorescent Pseudomonas strains. The gfp-tagging vector containing a gentamicin-resistance marker is useful for tagging strains carrying a Tn5 transposon. Tn5 transposons often carry kanamycin-resistance-encoding genes and are frequently used to generate bacterial mutants and to deliver reporter constructions in gene expression studies. To demonstrate the utility of a dual marker/reporter system, the Tn7-gfp marker system was combined with a Tn5-delivered luxAB reporter system in Pseudomonas fluorescens. The system allowed detection of gfp-tagged cells in the barley rhizosphere, while expression of the Tn5-tagged locus could be determined by measuring bioluminescence. | 2001 | 11348676 |
| 350 | 5 | 0.9944 | Random transposon vectors pUTTns for the markerless integration of exogenous genes into gram-negative eubacteria chromosomes. A set of random transposon vectors pUTTns that facilitates the markerless integration of new functions into the chromosome of gram-negative bacteria has been developed. The vectors, which are derived from mini-Tn5 transposons, are located on a R6K-based suicide delivery plasmid that provides the IS50(R) transposase tnp gene in cis, but they are external to the mobile element. The vectors' conjugal transfer to recipients is mediated by RP4 mobilization functions in the donor. Internal to the mini-Tn5 element is a cassette that contains a selectable antibiotic resistance marker (kanamycin, chloramphenicol, or tetracycline resistance gene), a counter-selectable marker (sacB), a 430-bp repeat of the sacB gene 3' end acted as the directly-repeated (DR) sequence, and modified multiple cloning sites (MCS). After two total rounds of transposon integration and recombination between the two DRs, only the exogenous DNA inserted into the MCS (passenger genes) and a single 430-bp scar sacBDR fragment remained in the chromosome after excision. The utility of these vectors was demonstrated by integrating the organophosphorus insecticide hydrolase gene (mpd) into the chromosome of Escherichia, Pseudomonas, Sphingomonas, and Paracoccus species. Sequential integration of another organophosphorus insecticide hydrolase gene (oph) into the previously engineered bacteria, without bringing any selectable markers, was also successful. These engineered bacteria were relatively stable. Cell viability and original degrading characteristics were not affected compared with the original recipients. This shows that the developed system is very useful for the markerless integration of exogenous genes into the chromosome of gram-negative eubacteria. | 2009 | 19778558 |
| 354 | 6 | 0.9943 | New cloning vectors to facilitate quick allelic exchange in gram-negative bacteria. New cloning vectors have been developed with features to enhance quick allelic exchange in gram-negative bacteria. The conditionally replicative R6K and transfer origins facilitate conjugation and chromosomal integration into a variety of bacterial species, whereas the sacB gene provides counterselection for allelic exchange. The vectors have incorporated the lacZ alpha fragment with an enhanced multicloning site for easy blue/white screening and priming sites identified for efficient in vivo assembly or other DNA assembly cloning techniques. Different antibiotic resistance markers allow versatility for use with different bacteria, and transformation into an Escherichia coli strain capable of conjugation enables a quick method for allelic exchange. As a proof of principle, the authors used these vectors to inactivate genes in Vibrio cholerae and Salmonella typhimurium. | 2021 | 33492170 |
| 289 | 7 | 0.9941 | A genetic system that reports transient activation of genes in Bacillus. Site-specific recombination is a powerful tool for precise excision of DNA fragments. We used this characteristic to construct a genetic system to report the transient activation of a promoter by promoting the stable acquisition of an antibiotic resistance marker by the bacterium. The system is composed of two compatible plasmid derivatives from Gram-positive bacteria. One of the plasmids allows the insertion of promoters upstream from tnpI, which encodes the site-specific recombinase of Tn4430. The second plasmid carries two selectable resistance genes: one is flanked by two site-specific recombination sequences and is lost following recombination; in contrast, the other resistance gene becomes functional after the site-specific recombination event. By inserting conditionally controlled promoters (the xylose-inducible xylA promoter or the plcA promoter whose expression is dependent on the growth medium) upstream of tnpI, we demonstrated that our genetic system responds to signals inducing transcription by conferring a new resistance phenotype to the host bacteria. Thus, this system can be used to identify genes which are transiently or conditionally expressed. | 1997 | 9427554 |
| 763 | 8 | 0.9941 | Inducing conformational preference of the membrane protein transporter EmrE through conservative mutations. Transporters from bacteria to humans contain inverted repeat domains thought to arise evolutionarily from the fusion of smaller membrane protein genes. Association between these domains forms the functional unit that enables transporters to adopt distinct conformations necessary for function. The small multidrug resistance (SMR) family provides an ideal system to explore the role of mutations in altering conformational preference since transporters from this family consist of antiparallel dimers that resemble the inverted repeats present in larger transporters. Here, we show using NMR spectroscopy how a single conservative mutation introduced into an SMR dimer is sufficient to change the resting conformation and function in bacteria. These results underscore the dynamic energy landscape for transporters and demonstrate how conservative mutations can influence structure and function. | 2019 | 31637997 |
| 3001 | 9 | 0.9941 | IS26 and the IS26 family: versatile resistance gene movers and genome reorganizers. SUMMARYIn Gram-negative bacteria, the insertion sequence IS26 is highly active in disseminating antibiotic resistance genes. IS26 can recruit a gene or group of genes into the mobile gene pool and support their continued dissemination to new locations by creating pseudo-compound transposons (PCTs) that can be further mobilized by the insertion sequence (IS). IS26 can also enhance expression of adjacent potential resistance genes. IS26 encodes a DDE transposase but has unique properties. It forms cointegrates between two separate DNA molecules using two mechanisms. The well-known copy-in (replicative) route generates an additional IS copy and duplicates the target site. The recently discovered and more efficient and targeted conservative mechanism requires an IS in both participating molecules and does not generate any new sequence. The unit of movement for PCTs, known as a translocatable unit or TU, includes only one IS26. TU formed by homologous recombination between the bounding IS26s can be reincorporated via either cointegration route. However, the targeted conservative reaction is key to generation of arrays of overlapping PCTs seen in resistant pathogens. Using the copy-in route, IS26 can also act on a site in the same DNA molecule, either inverting adjacent DNA or generating an adjacent deletion plus a circular molecule carrying the DNA segment lost and an IS copy. If reincorporated, these circular molecules create a new PCT. IS26 is the best characterized IS in the IS26 family, which includes IS257/IS431, ISSau10, IS1216, IS1006, and IS1008 that are also implicated in spreading resistance genes in Gram-positive and Gram-negative pathogens. | 2024 | 38436262 |
| 729 | 10 | 0.9940 | Extracellular DNA-induced antimicrobial peptide resistance mechanisms in Pseudomonas aeruginosa. Extracellular DNA (eDNA) is in the environment, bodily fluids, in the matrix of biofilms, and accumulates at infection sites. eDNA can function as a nutrient source, a universal biofilm matrix component, and an innate immune effector in eDNA traps. In biofilms, eDNA is required for attachment, aggregation, and stabilization of microcolonies. We have recently shown that eDNA can sequester divalent metal cations, which has interesting implications on antibiotic resistance. eDNA binds metal cations and thus activates the Mg(2+)-responsive PhoPQ and PmrAB two-component systems. In Pseudomonas aeruginosa and many other Gram-negative bacteria, the PhoPQ/PmrAB systems control various genes required for virulence and resisting killing by antimicrobial peptides (APs), including the pmr genes (PA3552-PA3559) that are responsible for the addition of aminoarabinose to lipid A. The PA4773-PA4775 genes are a second DNA-induced cluster and are required for the production of spermidine on the outer surface, which protects the outer membrane from AP treatment. Both modifications mask the negative surface charges and limit membrane damage by APs. DNA-enriched biofilms or planktonic cultures have increased antibiotic resistance phenotypes to APs and aminoglycosides. These dual antibiotic resistance and immune evasion strategies may be expressed in DNA-rich environments and contribute to long-term survival. | 2013 | 23419933 |
| 568 | 11 | 0.9940 | Conjugation Operons in Gram-Positive Bacteria with and without Antitermination Systems. Genes involved in the same cellular process are often clustered together in an operon whose expression is controlled by an upstream promoter. Generally, the activity of the promoter is strictly controlled. However, spurious transcription undermines this strict regulation, particularly affecting large operons. The negative effects of spurious transcription can be mitigated by the presence of multiple terminators inside the operon, in combination with an antitermination system. Antitermination systems modify the transcription elongation complexes and enable them to bypass terminators. Bacterial conjugation is the process by which a conjugative DNA element is transferred from a donor to a recipient cell. Conjugation involves many genes that are mostly organized in one or a few large operons. It has recently been shown that many conjugation operons present on plasmids replicating in Gram-positive bacteria possess a bipartite antitermination system that allows not only many terminators inside the conjugation operon to be bypassed, but also the differential expression of a subset of genes. Here, we show that some conjugation operons on plasmids belonging to the Inc18 family of Gram-positive broad host-range plasmids do not possess an antitermination system, suggesting that the absence of an antitermination system may have advantages. The possible (dis)advantages of conjugation operons possessing (or not) an antitermination system are discussed. | 2022 | 35336162 |
| 9985 | 12 | 0.9939 | Identification of the First Gene Transfer Agent (GTA) Small Terminase in Rhodobacter capsulatus and Its Role in GTA Production and Packaging of DNA. Genetic exchange mediated by viruses of bacteria (bacteriophages) is the primary driver of rapid bacterial evolution. The priority of viruses is usually to propagate themselves. Most bacteriophages use the small terminase protein to identify their own genome and direct its inclusion into phage capsids. Gene transfer agents (GTAs) are descended from bacteriophages, but they instead package fragments of the entire bacterial genome without preference for their own genes. GTAs do not selectively target specific DNA, and no GTA small terminases are known. Here, we identified the small terminase from the model Rhodobacter capsulatus GTA, which then allowed prediction of analogues in other species. We examined the role of the small terminase in GTA production and propose a structural basis for random DNA packaging.IMPORTANCE Random transfer of any and all genes between bacteria could be influential in the spread of virulence or antimicrobial resistance genes. Discovery of the true prevalence of GTAs in sequenced genomes is hampered by their apparent similarity to bacteriophages. Our data allowed the prediction of small terminases in diverse GTA producer species, and defining the characteristics of a "GTA-type" terminase could be an important step toward novel GTA identification. Importantly, the GTA small terminase shares many features with its phage counterpart. We propose that the GTA terminase complex could become a streamlined model system to answer fundamental questions about double-stranded DNA (dsDNA) packaging by viruses that have not been forthcoming to date. | 2019 | 31534034 |
| 286 | 13 | 0.9939 | Plasmid rescue - a tool for reproducible recovery of genes from transfected mammalian cells? The efficient rescue of plasmids containing the thymidine kinase gene (tk) of Herpes simplex virus type I from genetically transformed mouse cells by transformation of bacteria is described. Rescued plasmids contain insertions of calf DNA used as a carrier in the transfection but usually lack portions of plasmid DNA. Deletions generally concern the region spanning from around the PvuII site of pBR322 to within the tetracycline resistance coding sequence, whereas the extent of tk sequence deletion varies, depending on the site of its integration (BamHI or PvuII) into the plasmid. Modelling the rescue process by transformation of bacteria with a mixture of original plasmids and sheared mouse cell DNA clearly demonstrates that deletions are caused by the presence of the mammalian DNA and they probably occur during re-transformation of bacteria before the onset of tetracycline gene expression. Plasmids lacking the Tcr region are reproducibly rescuable without deletion. Methods for reproducible re-isolation of transferred genes from mammalian cells are discussed. | 1984 | 6323922 |
| 348 | 14 | 0.9939 | Conjugative DNA transfer in Streptomyces by TraB: is one protein enough? Antibiotic-producing soil bacteria of the genus Streptomyces form a huge natural reservoir of antibiotic resistance genes for the dissemination within the soil community. Streptomyces plasmids encode a unique conjugative DNA transfer system clearly distinguished from classical conjugation involving a single-stranded DNA molecule and a type IV protein secretion system. Only a single plasmid-encoded protein, TraB, is sufficient to translocate a double-stranded DNA molecule into the recipient in Streptomyces matings. TraB is a hexameric pore-forming ATPase that resembles the chromosome segregator protein FtsK and translocates DNA by recognizing specific 8-bp repeats present in the plasmid clt locus. Mobilization of chromosomal genes does not require integration of the plasmid, because TraB also recognizes clt-like sequences distributed all over the chromosome. | 2012 | 23082971 |
| 177 | 15 | 0.9939 | Bacterial mercury resistance from atoms to ecosystems. Bacterial resistance to inorganic and organic mercury compounds (HgR) is one of the most widely observed phenotypes in eubacteria. Loci conferring HgR in Gram-positive or Gram-negative bacteria typically have at minimum a mercuric reductase enzyme (MerA) that reduces reactive ionic Hg(II) to volatile, relatively inert, monoatomic Hg(0) vapor and a membrane-bound protein (MerT) for uptake of Hg(II) arranged in an operon under control of MerR, a novel metal-responsive regulator. Many HgR loci encode an additional enzyme, MerB, that degrades organomercurials by protonolysis, and one or more additional proteins apparently involved in transport. Genes conferring HgR occur on chromosomes, plasmids, and transposons and their operon arrangements can be quite diverse, frequently involving duplications of the above noted structural genes, several of which are modular themselves. How this very mobile and plastic suite of proteins protects host cells from this pervasive toxic metal, what roles it has in the biogeochemical cycling of Hg, and how it has been employed in ameliorating environmental contamination are the subjects of this review. | 2003 | 12829275 |
| 380 | 16 | 0.9938 | Expression of a chloramphenicol-resistance determinant carried on hybrid plasmids in gram-positive and gram-negative bacteria. To analyse the control of chloramphenicol (Cm) resistance conferred by the Staphylococcus aureus plasmid pUB112, a detailed restriction map of this plasmid has been constructed, and the position and orientation of the cat gene have been determined. An MboI restriction fragment carrying the entire cat gene of pUB112 was then cloned in another S. aureus plasmid, the kanamycin (Km) resistance vector pUB110. Depending on the orientation of the incorporated cat fragment, the level of Cm resistance varied dramatically in Bacillus subtilis cells. This effect could not be eliminated by deleting parts of the vector DNA, and only the introduction of a transcription termination signal led to orientation-independent Cm resistance. One such construct was further developed to yield a shuttle vector, replicating both in Escherichia coli and B. subtilis. Using this vector the expression of incorporated genes can be determined in both Gram-positive and Gram-negative bacteria. By in vitro transcription experiments using pUB110 DNA linearized with various restriction endonucleases as template, two pUB110 promoters could be localized and their orientations determined: one promoter controls a gene whose function is unknown, the other regulates the transcription of the KmR gene. | 1984 | 6442250 |
| 9332 | 17 | 0.9938 | Intercellular nanotubes mediate bacterial communication. Bacteria are known to communicate primarily via secreted extracellular factors. Here we identify a previously uncharacterized type of bacterial communication mediated by nanotubes that bridge neighboring cells. Using Bacillus subtilis as a model organism, we visualized transfer of cytoplasmic fluorescent molecules between adjacent cells. Additionally, by coculturing strains harboring different antibiotic resistance genes, we demonstrated that molecular exchange enables cells to transiently acquire nonhereditary resistance. Furthermore, nonconjugative plasmids could be transferred from one cell to another, thereby conferring hereditary features to recipient cells. Electron microscopy revealed the existence of variously sized tubular extensions bridging neighboring cells, serving as a route for exchange of intracellular molecules. These nanotubes also formed in an interspecies manner, between B. subtilis and Staphylococcus aureus, and even between B. subtilis and the evolutionary distant bacterium Escherichia coli. We propose that nanotubes represent a major form of bacterial communication in nature, providing a network for exchange of cellular molecules within and between species. | 2011 | 21335240 |
| 391 | 18 | 0.9938 | New derivatives of transposon Tn5 suitable for mobilization of replicons, generation of operon fusions and induction of genes in gram-negative bacteria. Three types of new variants of the broad-host-range transposon Tn5 are described. (i) Tn5-mob derivatives with the new selective resistance (R) markers GmR, SpR and TcR facilitate the efficient mobilization of replicons within a wide range of Gram-negative bacteria. (ii) Promoter probe transposons carry the promoterless reporter genes lacZ, nptII, or luc, and NmR, GmR or TcR as selective markers. These transposons can be used to generate transcriptional fusions upon insertion, thus facilitating accurate determinations of gene expression. (iii) Tn5-P-out derivatives carry the npt- or tac-promoter reading out from the transposon, and TcR, NmR or GmR genes. These variants allow the constitutive expression of downstream genes. The new Tn5 variants are available on mobilizable Escherichia coli vectors suitable as suicidal carriers for transposon mutagenesis of non-E. coli recipients and some on a phage lambda mutant to be used for transposon mutagenesis in E. coli. | 1989 | 2551782 |
| 9852 | 19 | 0.9938 | Transposase-DNA Complex Structures Reveal Mechanisms for Conjugative Transposition of Antibiotic Resistance. Conjugative transposition drives the emergence of multidrug resistance in diverse bacterial pathogens, yet the mechanisms are poorly characterized. The Tn1549 conjugative transposon propagates resistance to the antibiotic vancomycin used for severe drug-resistant infections. Here, we present four high-resolution structures of the conserved Y-transposase of Tn1549 complexed with circular transposon DNA intermediates. The structures reveal individual transposition steps and explain how specific DNA distortion and cleavage mechanisms enable DNA strand exchange with an absolute minimum homology requirement. This appears to uniquely allow Tn916-like conjugative transposons to bypass DNA homology and insert into diverse genomic sites, expanding gene transfer. We further uncover a structural regulatory mechanism that prevents premature cleavage of the transposon DNA before a suitable target DNA is found and generate a peptide antagonist that interferes with the transposase-DNA structure to block transposition. Our results reveal mechanistic principles of conjugative transposition that could help control the spread of antibiotic resistance genes. | 2018 | 29551265 |