# | Rank | Similarity | Title + Abs. | Year | PMID |
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 |
| 348 | 0 | 0.9919 | 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 |
| 349 | 1 | 0.9918 | 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 |
| 3001 | 2 | 0.9917 | 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 |
| 3003 | 3 | 0.9914 | IS26-Mediated Formation of Transposons Carrying Antibiotic Resistance Genes. The IS26 transposase, Tnp26, catalyzes IS26 movement to a new site and deletion or inversion of adjacent DNA via a replicative route. The intramolecular deletion reaction produces a circular molecule consisting of a DNA segment and a single IS26, which we call a translocatable unit or TU. Recently, Tnp26 was shown to catalyze an additional intermolecular, conservative reaction between two preexisting copies of IS26 in different plasmids. Here, we have investigated the relative contributions of homologous recombination and Tnp26-catalyzed reactions to the generation of a transposon from a TU. Circular TUs containing the aphA1a kanamycin and neomycin resistance gene or the tet(D) tetracycline resistance determinant were generated in vitro and transformed into Escherichia coli recA cells carrying R388::IS26. The TU incorporated next to the IS26 in R388::IS26 forms a transposon with the insertion sequence (IS) in direct orientation. Introduction of a second TU produced regions containing both the aphA1a gene and the tet(D) determinant in either order but with only three copies of IS26. The integration reaction, which required a preexisting IS26, was precise and conservative and was 50-fold more efficient when both IS26 copies could produce an active Tnp26. When both ISs were inactivated by a frameshift in tnp26, TU incorporation was not detected in E. coli recA cells, but it did occur in E. coli recA (+) cells. However, the Tnp-catalyzed reaction was 100-fold more efficient than RecA-dependent homologous recombination. The ability of Tnp26 to function in either a replicative or conservative mode is likely to explain the prominence of IS26-bounded transposons in the resistance regions found in Gram-negative bacteria. IMPORTANCE In Gram-negative bacteria, IS26 recruits antibiotic resistance genes into the mobile gene pool by forming transposons carrying many different resistance genes. In addition to replicative transposition, IS26 was recently shown to use a novel conservative movement mechanism in which an incoming IS26 targets a preexisting one. Here, we have demonstrated how IS26-bounded class I transposons can be produced from translocatable units (TUs) containing only an IS26 and a resistance gene via the conservative reaction. TUs were incorporated next to an existing IS26, creating a class I transposon, and if the targeted IS26 is in a transposon, the product resembles two transposons sharing a central IS26, a configuration observed in some resistance regions and when a transposon is tandemly duplicated. Though homologous recombination could also incorporate a TU, Tnp26 is far more efficient. This provides insight into how IS26 builds transposons and brings additional transposons into resistance regions. | 2016 | 27303727 |
| 9977 | 4 | 0.9914 | IncC conjugative plasmids and SXT/R391 elements repair double-strand breaks caused by CRISPR-Cas during conjugation. Bacteria have evolved defence mechanisms against bacteriophages. Restriction-modification systems provide innate immunity by degrading invading DNAs that lack proper methylation. CRISPR-Cas systems provide adaptive immunity by sampling the genome of past invaders and cutting the DNA of closely related DNA molecules. These barriers also restrict horizontal gene transfer mediated by conjugative plasmids. IncC conjugative plasmids are important contributors to the global dissemination of multidrug resistance among pathogenic bacteria infecting animals and humans. Here, we show that IncC conjugative plasmids are highly resilient to host defence systems during entry into a new host by conjugation. Using a TnSeq strategy, we uncover a conserved operon containing five genes (vcrx089-vcrx093) that confer a novel host defence evasion (hde) phenotype. We show that vcrx089-vcrx090 promote resistance against type I restriction-modification, whereas vcrx091-vcxr093 promote CRISPR-Cas evasion by repairing double-strand DNA breaks via recombination between short sequence repeats. vcrx091, vcrx092 and vcrx093 encode a single-strand binding protein, and a single-strand annealing recombinase and double-strand exonuclease related to Redβ and λExo of bacteriophage λ, respectively. Homologous genes of the integrative and conjugative element R391 also provide CRISPR-Cas evasion. Hence, the conserved hde operon considerably broadens the host range of large families of mobile elements spreading multidrug resistance. | 2020 | 32556263 |
| 391 | 5 | 0.9912 | 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 |
| 3004 | 6 | 0.9911 | IS26-Mediated Precise Excision of the IS26-aphA1a Translocatable Unit. We recently showed that, in the absence of RecA-dependent homologous recombination, the Tnp26 transposase catalyzes cointegrate formation via a conservative reaction between two preexisting IS26, and this is strongly preferred over replicative transposition to a new site. Here, the reverse reaction was investigated by assaying for precise excision of the central region together with a single IS26 from a compound transposon bounded by IS26. In a recA mutant strain, Tn4352, a kanamycin resistance transposon carrying the aphA1a gene, was stable. However, loss of kanamycin resistance due to precise excision of the translocatable unit (TU) from the closely related Tn4352B, leaving behind the second IS26, occurred at high frequency. Excision occurred when Tn4352B was in either a high- or low-copy-number plasmid. The excised circular segment, known as a TU, was detected by PCR. Excision required the IS26 transposase Tnp26. However, the Tnp26 of only one IS26 in Tn4352B was required, specifically the IS26 downstream of the aphA1a gene, and the excised TU included the active IS26. The frequency of Tn4352B TU loss was influenced by the context of the transposon, but the critical determinant of high-frequency excision was the presence of three G residues in Tn4352B replacing a single G in Tn4352. These G residues are located immediately adjacent to the two G residues at the left end of the IS26 that is upstream of the aphA1a gene. Transcription of tnp26 was not affected by the additional G residues, which appear to enhance Tnp26 cleavage at this end. IMPORTANCE: Resistance to antibiotics limits treatment options. In Gram-negative bacteria, IS26 plays a major role in the acquisition and dissemination of antibiotic resistance. IS257 (IS431) and IS1216, which belong to the same insertion sequence (IS) family, mobilize resistance genes in staphylococci and enterococci, respectively. Many different resistance genes are found in compound transposons bounded by IS26, and multiply and extensively antibiotic-resistant Gram-negative bacteria often include regions containing several antibiotic resistance genes and multiple copies of IS26. We recently showed that in addition to replicative transposition, IS26 can use a conservative movement mechanism in which an incoming IS26 targets a preexisting one, and this reaction can create these regions. This mechanism differs from that of all the ISs examined in detail thus far. Here, we have continued to extend understanding of the reactions carried out by IS26 by examining whether the reverse precise excision reaction is also catalyzed by the IS26 transposase. | 2015 | 26646012 |
| 9876 | 7 | 0.9911 | The Facts and Family Secrets of Plasmids That Replicate via the Rolling-Circle Mechanism. Plasmids are self-replicative DNA elements that are transferred between bacteria. Plasmids encode not only antibiotic resistance genes but also adaptive genes that allow their hosts to colonize new niches. Plasmid transfer is achieved by conjugation (or mobilization), phage-mediated transduction, and natural transformation. Thousands of plasmids use the rolling-circle mechanism for their propagation (RCR plasmids). They are ubiquitous, have a high copy number, exhibit a broad host range, and often can be mobilized among bacterial species. Based upon the replicon, RCR plasmids have been grouped into several families, the best known of them being pC194 and pUB110 (Rep_1 family), pMV158 and pE194 (Rep_2 family), and pT181 and pC221 (Rep_trans family). Genetic traits of RCR plasmids are analyzed concerning (i) replication mediated by a DNA-relaxing initiator protein and its interactions with the cognate DNA origin, (ii) lagging-strand origins of replication, (iii) antibiotic resistance genes, (iv) mobilization functions, (v) replication control, performed by proteins and/or antisense RNAs, and (vi) the participating host-encoded functions. The mobilization functions include a relaxase initiator of transfer (Mob), an origin of transfer, and one or two small auxiliary proteins. There is a family of relaxases, the MOB(V) family represented by plasmid pMV158, which has been revisited and updated. Family secrets, like a putative open reading frame of unknown function, are reported. We conclude that basic research on RCR plasmids is of importance, and our perspectives contemplate the concept of One Earth because we should incorporate bacteria into our daily life by diminishing their virulence and, at the same time, respecting their genetic diversity. | 2022 | 34878299 |
| 9843 | 8 | 0.9911 | Conjugative transposons: an unusual and diverse set of integrated gene transfer elements. Conjugative transposons are integrated DNA elements that excise themselves to form a covalently closed circular intermediate. This circular intermediate can either reintegrate in the same cell (intracellular transposition) or transfer by conjugation to a recipient and integrate into the recipient's genome (intercellular transposition). Conjugative transposons were first found in gram-positive cocci but are now known to be present in a variety of gram-positive and gram-negative bacteria also. Conjugative transposons have a surprisingly broad host range, and they probably contribute as much as plasmids to the spread of antibiotic resistance genes in some genera of disease-causing bacteria. Resistance genes need not be carried on the conjugative transposon to be transferred. Many conjugative transposons can mobilize coresident plasmids, and the Bacteroides conjugative transposons can even excise and mobilize unlinked integrated elements. The Bacteroides conjugative transposons are also unusual in that their transfer activities are regulated by tetracycline via a complex regulatory network. | 1995 | 8531886 |
| 429 | 9 | 0.9911 | An integrative vector exploiting the transposition properties of Tn1545 for insertional mutagenesis and cloning of genes from gram-positive bacteria. We have constructed and used an integrative vector, pAT112, that takes advantage of the transposition properties (integration and excision) of transposon Tn1545. This 4.9-kb plasmid is composed of: (i) the replication origin of pACYC184; (ii) the attachment site (att) of Tn1545; (iii) erythromycin-and kanamycin-resistance-encoding genes for selection in Gram- and Gram+ bacteria; and (iv) the transfer origin of IncP plasmid RK2, which allows mobilization of the vector from Escherichia coli to various Gram+ recipients. Integration of pAT112 requires the presence of the transposon-encoded integrase, Int-Tn, in the new host. This vector retains the insertion specificity of the parental element Tn1545 and utilises it to carry out insertional mutagenesis, as evaluated in Enterococcus faecalis. Since pAT112 contains the pACYC184 replicon and lacks most of the restriction sites that are commonly used for molecular cloning, a gene from a Gram+ bacterium disrupted with this vector can be recovered in E. coli by cleavage of genomic DNA, intramolecular ligation and transformation. Regeneration of the gene, by excision of pAT112, can be obtained in an E. coli strain expressing the excisionase and integrase of Tn1545. The functionality of this system was illustrated by characterization of an IS30-like structure in the chromosome of En. faecalis. Derivatives pAT113 and pAT114 contain ten unique cloning sites that allow screening of recombinants having DNA inserts by alpha-complementation in E. coli carrying the delta M15 deletion of lacZ alpha. These vectors are useful to clone and introduce foreign genes into the genomes of Gram+ bacteria. | 1991 | 1657722 |
| 379 | 10 | 0.9911 | Broad host range DNA cloning system for gram-negative bacteria: construction of a gene bank of Rhizobium meliloti. A broad host range cloning vehicle that can be mobilized at high frequency into Gram-negative bacteria has been constructed from the naturally occurring antibiotic resistance plasmid RK2. The vehicle is 20 kilobase pairs in size, encodes tetracycline resistance, and contains two single restriction enzyme sites suitable for cloning. Mobilization is effected by a helper plasmid consisting of the RK2 transfer genes linked to a ColE1 replicon. By use of this plasmid vehicle, a gene bank of the DNA from a wild-type strain of Rhizobium meliloti has been constructed and established in Escherichia coli. One of the hybrid plasmids in the bank contains a DNA insert of approximately 26 kilobase pairs which has homology to the nitrogenase structural gene region of Klebsiella pneumoniae. | 1980 | 7012838 |
| 126 | 11 | 0.9910 | Single-gene knockout of a novel regulatory element confers ethionine resistance and elevates methionine production in Corynebacterium glutamicum. Despite the availability of genome data and recent advances in methionine regulation in Corynebacterium glutamicum, sulfur metabolism and its underlying molecular mechanisms are still poorly characterized in this organism. Here, we describe the identification of an ORF coding for a putative regulatory protein that controls the expression of genes involved in sulfur reduction dependent on extracellular methionine levels. C. glutamicum was randomly mutagenized by transposon mutagenesis and 7,000 mutants were screened for rapid growth on agar plates containing the methionine antimetabolite D,L-ethionine. In all obtained mutants, the site of insertion was located in the ORF NCgl2640 of unknown function that has several homologues in other bacteria. All mutants exhibited similar ethionine resistance and this phenotype could be transferred to another strain by the defined deletion of the NCgl2640 gene. Moreover, inactivation of NCgl2640 resulted in significantly increased methionine production. Using promoter lacZ-fusions of genes involved in sulfur metabolism, we demonstrated the relief of L-methionine repression in the NCgl2640 mutant for cysteine synthase, o-acetylhomoserine sulfhydrolase (metY) and sulfite reductase. Complementation of the mutant strain with plasmid-borne NCgl2640 restored the wild-type phenotype for metY and sulfite reductase. | 2005 | 15668756 |
| 179 | 12 | 0.9910 | The genetics and biochemistry of mercury resistance. The ability of bacteria to detoxify mercurial compounds by reduction and volatilization is conferred by mer genes, which are usually plasmid located. The narrow spectrum (Hg2+ detoxifying) Tn501 and R100 determinants have been subjected to molecular genetic and DNA sequence analysis. Biochemical studies on the flavoprotein mercuric reductase have elucidated the mechanism of reduction of Hg2+ to Hg0. The mer genes have been mapped and sequenced and their protein products studied in minicells. Based on the deduced amino acid sequences, these proteins have been assigned a role in a mechanistic scheme for mercury flux in resistant bacteria. The mer genes are inducible, with regulatory control being exerted at the transcriptional level both positively and negatively. Attention is now focusing on broad-spectrum resistance involving detoxification of organomercurials by an additional enzyme, organomercurial lyase. Lyase genes have recently been cloned and sequencing studies are in progress. | 1987 | 2827958 |
| 760 | 13 | 0.9910 | The underling mechanism of bacterial TetR/AcrR family transcriptional repressors. Bacteria transcriptional regulators are classified by their functional and sequence similarities. Member of the TetR/AcrR family is two-domain proteins including an N-terminal HTH DNA-binding motif and a C-terminal ligand recognition domain. The C-terminal ligand recognition domain can recognize the very same compounds as their target transporters transferred. TetRs act as chemical sensors to monitor both the cellular environmental dynamics and their regulated genes underlying many events, such as antibiotics production, osmotic stress, efflux pumps, multidrug resistance, metabolic modulation, and pathogenesis. Compounds targeting Mycobacterium tuberculosis ethR represent promising novel antibiotic potentiater. TetR-mediated multidrug efflux pumps regulation might be good target candidate for the discovery of better new antibiotics against drug resistance. | 2013 | 23602932 |
| 352 | 14 | 0.9910 | 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 |
| 351 | 15 | 0.9909 | Rapid and efficient cloning of proviral flanking fragments by kanamycin resistance gene complementation. We have developed a technique for the rapid cloning of unknown flanking regions of transgenic DNA. We complemented a truncated kanamycin resistance gene of a bacterial plasmid with a neomycin resistance gene fragment from a gene transfer vector. Optimized transformation conditions allowed us to directly select for kanamycin-resistant bacteria. We cloned numerous proviral flanking fragments from growth factor-independent cell mutants that were obtained after infection with a replication incompetent retroviral vector and identified integrations into the cyclin D2 and several unknown genomic sequences. We anticipate that our method could be adapted to various vector systems that are used to tag and identify genes and to map genomes. | 1999 | 9863001 |
| 9833 | 16 | 0.9909 | Evolution of satellite plasmids can prolong the maintenance of newly acquired accessory genes in bacteria. Transmissible plasmids spread genes encoding antibiotic resistance and other traits to new bacterial species. Here we report that laboratory populations of Escherichia coli with a newly acquired IncQ plasmid often evolve 'satellite plasmids' with deletions of accessory genes and genes required for plasmid replication. Satellite plasmids are molecular parasites: their presence reduces the copy number of the full-length plasmid on which they rely for their continued replication. Cells with satellite plasmids gain an immediate fitness advantage from reducing burdensome expression of accessory genes. Yet, they maintain copies of these genes and the complete plasmid, which potentially enables them to benefit from and transmit the traits they encode in the future. Evolution of satellite plasmids is transient. Cells that entirely lose accessory gene function or plasmid mobility dominate in the long run. Satellite plasmids also evolve in Snodgrassella alvi colonizing the honey bee gut, suggesting that this mechanism may broadly contribute to the importance of IncQ plasmids as agents of bacterial gene transfer in nature. | 2019 | 31863068 |
| 6176 | 17 | 0.9909 | Involvement of GcvB small RNA in intrinsic resistance to multiple aminoglycoside antibiotics in Escherichia coli. Deleting the gene for small RNA GcvB in Escherichia coli was found to increase the sensitivity to several aminoglycoside antibiotics, such as neomycin, streptomycin, kanamycin, kasugamycin and spectinomycin, at low concentrations. GcvB, conserved in gram-negative enteric bacteria, is known to negatively control the expression of many genes for amino acid incorporation systems, especially the periplasmic ABC-transporter proteins. Deletions of several amino acid transporter genes in ΔgcvB cells decreased the antibiotic sensitivity to the wild-type level, suggesting that those genes are involved in uptake of aminoglycosides into the cell. Since GcvB is constitutively synthesized in growing cells, repressing synthesis of amino acid transporters, it contributes to the intrinsic resistance to several aminoglycoside antibiotics. | 2021 | 33169170 |
| 3002 | 18 | 0.9909 | An IS26 variant with enhanced activity. The insertion sequence IS26 plays a major role in the mobilization, expression and dissemination of antibiotic resistance genes in Gram-negative bacteria. Though IS26 is abundant in sequenced genomes and in plasmids that harbour antibiotic resistance genes, only a few minor variations in the IS26 sequence have been recorded. The most common variant, IS26* (also known as IS15Δ1), encodes a Tnp26 transposase with a single amino acid substitution, G184N in the catalytic domain. Using computational modelling, this substitution was predicted to increase the length of the helix that includes the E173 residue of the catalytic DDE triad, and its effect on activity was tested. An IS26 mutant generated in vitro producing Tnp26-G184N formed cointegrates in a standard untargeted reaction at 5-fold higher frequency than IS26 producing Tnp26. When the target included a single copy of IS26, the G184N substitution increased the cointegration frequency 10-fold and the reaction was targeted and conservative. Hence, the substitution increased Tnp26 activity. The longer helix may stabilise the position of the E173 of the DDE for the catalysis reaction and the specific G184N substitution may also enhance activity by increasing binding to the terminal inverted repeats. | 2019 | 30753435 |
| 395 | 19 | 0.9909 | O-antigen protects gram-negative bacteria from histone killing. Beyond their traditional role of wrapping DNA, histones display antibacterial activity to Gram-negative and -positive bacteria. To identify bacterial components that allow survival to a histone challenge, we selected resistant bacteria from homologous Escherichia coli libraries that harbor plasmids carrying pieces of the chromosome in different sizes. We identified genes required for exopolysaccharide production and for the synthesis of the polysaccharide domain of the lipopolysaccharide, called O-antigen. Indeed, O-antigen and exopolysaccharide conferred further resistance to histones. Notably, O-antigen also conferred resistance to histones in the pathogens Shigella flexneri and Klebsiella pneumoniae. | 2013 | 23951089 |