Publications
| Title | Abstract | Year(sorted descending) Filter | PMID Filter |
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| chemical shift assignments of a reduced n-terminal truncation mutant of the disulfide bond isomerase trbb from plasmid f, trbbδ29. | trbb from the conjugative plasmid f is a 181-residue disulfide bond isomerase that plays a role in the correct folding and maintenance of disulfide bonds within f plasmid encoded proteins in the bacterial periplasm. as a member of the thioredoxin-like superfamily, trbb has a predicted thioredoxin-like fold that contains a c-x-x-c active site required for performing specific redox chemistries on protein substrates. here we report the sequence-specific assignments of the reduced form of the n-term ... | 2014 | 24771093 |
| a high security double lock and key mechanism in huh relaxases controls orit-processing for plasmid conjugation. | relaxases act as dna selection sieves in conjugative plasmid transfer. most plasmid relaxases belong to the huh endonuclease family. trwc, the relaxase of plasmid r388, is the prototype of the huh relaxase family, which also includes trai of plasmid f. in this article we demonstrate that trwc processes its target nic-site by means of a highly secure double lock and key mechanism. it is controlled both by trwc-dna intermolecular interactions and by intramolecular dna interactions between several ... | 2014 | 25123661 |
| metagenomic chromosome conformation capture (meta3c) unveils the diversity of chromosome organization in microorganisms. | genomic analyses of microbial populations in their natural environment remain limited by the difficulty to assemble full genomes of individual species. consequently, the chromosome organization of microorganisms has been investigated in a few model species, but the extent to which the features described can be generalized to other taxa remains unknown. using controlled mixes of bacterial and yeast species, we developed meta3c, a metagenomic chromosome conformation capture approach that allows ch ... | 2014 | 25517076 |
| crispr-cas systems preferentially target the leading regions of mobf conjugative plasmids. | most prokaryotes contain crispr-cas immune systems that provide protection against mobile genetic elements. we have focused on the ability of crispr-cas to block plasmid conjugation, and analyzed the position of target sequences (protospacers) on conjugative plasmids. the analysis reveals that protospacers are non-uniformly distributed over plasmid regions in a pattern that is determined by the plasmid's mobilization type (mob). while mobp plasmids are most frequently targeted in the region ente ... | 2013 | 23535265 |
| thioredoxin-like proteins in f and other plasmid systems. | bacterial conjugation is the process by which a conjugative plasmid transfers from donor to recipient bacterium. during this process, single-stranded plasmid dna is actively and specifically transported from the cytoplasm of the donor, through a large membrane-spanning assembly known as the pore complex, and into the cytoplasm of the recipient. in gram negative bacteria, construction of the pore requires localization of a subset of structural and catalytically active proteins to the bacterial pe ... | 2013 | 23721857 |
| insight into centromere-binding properties of parb proteins: a secondary binding motif is essential for bacterial genome maintenance. | parb proteins are one of the three essential components of partition systems that actively segregate bacterial chromosomes and plasmids. in binding to centromere sequences, parb assembles as nucleoprotein structures called partition complexes. these assemblies are the substrates for the partitioning process that ensures dna molecules are segregated to both sides of the cell. we recently identified the sopc centromere nucleotides required for binding to the parb homologue of plasmid f, sopb. this ... | 2013 | 23345617 |
| characterization of the phd-doc and ccd toxin-antitoxin cassettes from vibrio superintegrons. | toxin-antitoxin (ta) systems have been reported in the genomes of most bacterial species, and their role when located on the chromosome is still debated. ta systems are particularly abundant in the massive cassette arrays associated with chromosomal superintegrons (si). here, we describe the characterization of two superintegron cassettes encoding putative ta systems. the first is the phd-doc(si) system identified in vibrio cholerae n16961. we determined its distribution in 36 v. cholerae strain ... | 2013 | 23475970 |
| structural insights into the chaperone activity of the 40-kda heat shock protein dnaj: binding and remodeling of a native substrate. | hsp40 chaperones bind and transfer substrate proteins to hsp70s and regulate their atpase activity. the interaction of hsp40s with native proteins modifies their structure and function. a good model for this function is dnaj, the bacterial hsp40 that interacts with repe, the repressor/activator of plasmid f replication, and together with dnak regulates its function. we characterize here the structure of the dnaj-repe complex by electron microscopy, the first described structure of a complex betw ... | 2013 | 23580641 |
| diversity of pili-specific bacteriophages: genome sequence of incm plasmid-dependent rna phage m. | bacteriophages of the leviviridae family are small rna viruses with linear, positive-sense, single-stranded rna genomes that encode only four proteins. all phages of this family require bacterial pili to attach to and infect cells. leviviridae phages utilizing f-pili for this purpose have been extensively studied. rna phages specific for conjugative plasmid-encoded pili other than that of plasmid f have been isolated, but are much less understood and their relation to the f-pili-specific phages ... | 2012 | 23176223 |
| a common origin for the bacterial toxin-antitoxin systems pard and ccd, suggested by analyses of toxin/target and toxin/antitoxin interactions. | bacterial toxin-antitoxin (ta) systems encode two proteins, a potent inhibitor of cell proliferation (toxin) and its specific antidote (antitoxin). structural data has revealed striking similarities between the two model ta toxins ccdb, a dna gyrase inhibitor encoded by the ccd system of plasmid f, and kid, a site-specific endoribonuclease encoded by the pard system of plasmid r1. while a common structural fold seemed at odds with the two clearly different modes of action of these toxins, the po ... | 2012 | 23029540 |
| differences in unfolding energetics of ccdb toxins from v. fischeri and e. coli. | ccd system is a toxin-antitoxin module (operon) located on plasmids and chromosomes of bacteria. ccdbf encoded by ccd operon located on escherichia coli plasmid f and ccdbvfi encoded by ccd operon located on vibrio fischeri chromosome are members of the ccdb family of toxins. native ccdbs are dimers that bind to gyrase-dna complexes and inhibit dna transcription and replication. while thermodynamic stability and unfolding characteristics of the plasmidic ccdbf in denaturant solutions are reporte ... | 2012 | 24061309 |
| An activation domain of plasmid R1 TraI protein delineates stages of gene transfer initiation. | Bacterial conjugation is a form of type IV secretion that transports protein and DNA to recipient cells. Specific bacteriophage exploit the conjugative pili and cell envelope spanning protein machinery of these systems to invade bacterial cells. Infection by phage R17 requires F-like pili and coupling protein TraD, which gates the cytoplasmic entrance of the secretion channel. Here we investigate the role of TraD in R17 nucleoprotein uptake and find parallels to secretion mechanisms. The relaxos ... | 2011 | 22066957 |
| effect of extremely low frequency magnetic field exposure on dna transposition in relation to frequency, wave shape and exposure time. | purpose: to examine the effect of extremely low frequency magnetic field (elf-mf) exposure on transposon (tn) mobility in relation to the exposure time, the frequency and the wave shape of the field applied. materials and methods: two escherichia coli model systems were used: (1) cells unable to express β-galactosidase (lacz(-)), containing a mini-transposon tn10 element able to give ability to express β-galactosidase (lacz(+)) upon its transposition; therefore in these cells transposition activ ... | 2011 | 21504343 |
| centromere binding specificity in assembly of the f plasmid partition complex. | the segregation of plasmid f of escherichia coli is highly reliable. the sop partition locus, responsible for this stable maintenance, is composed of two genes, sopa and sopb and a centromere, sopc, consisting of 12 direct repeats of 43 bp. each repeat carries a 16-bp inverted repeat motif to which sopb binds to form a nucleoprotein assembly called the partition complex. a database search for sequences closely related to sopc revealed unexpected features that appeared highly conserved. we have i ... | 2011 | 21653553 |
| trbb from conjugative plasmid f is a structurally distinct disulfide isomerase that requires dsbd for redox state maintenance. | trbb, a periplasmic protein encoded by the conjugative plasmid f, has a predicted thioredoxin-like fold and possesses a c-x-x-c redox active site motif. trbb may function in the conjugative process by serving as a disulfide bond isomerase, facilitating proper folding of a subset of f-plasmid-encoded proteins in the periplasm. previous studies have demonstrated that a +ötrbb f plasmid in escherichia coli lacking dsbc(e.coli), its native disulfide bond isomerase, experiences a 10-fold decrease in ... | 2011 | 21742866 |
| the transfer operon of plasmid r1 extends beyond fino into the downstream replication genes. | fino is the final gene in the 35.4 kb transfer operon of incfi plasmid f that is known to be involved in self-conjugative transfer. the genetic region distal to fino separates the conjugation and replication control modules of incfii plasmid r100 and carries uncharacterized genes not found in plasmid f. however, comparison of the r100 gene organization with database entries of f-like plasmids suggests its broad conservation. we determined the dna sequence of this region of incfii plasmid r1 and ... | 2010 | 21145348 |
| pard toxin-antitoxin system of plasmid r1--basic contributions, biotechnological applications and relationships with closely-related toxin-antitoxin systems. | toxin-antitoxin systems, as found in bacterial plasmids and their host chromosomes, play a role in the maintenance of genetic information, as well as in the response to stress. we describe the basic biology of the pard/kiskid toxin-antitoxin system of escherichia coli plasmid r1, with an emphasis on regulation, toxin activity, potential applications in biotechnology and its relationships with related toxin-antitoxin systems. special reference is given to the ccd toxin-antitoxin system of plasmid ... | 2010 | 20569269 |
| characterization and global gene expression of f- phenocopies during escherichia coli biofilm formation. | the ecological role of horizontal gene transfer within biofilms has been recently investigated, and it has been reported that conjugation directly induces bacteria to form biofilms via expression of conjugative pili. in this report, we described the contribution of bacterial conjugation during biofilm formation by escherichia coli harboring a natural incf conjugative f plasmid (f(+)). we showed that cell-to-cell pili interactions through the homosexual mating-pair formation among f(+) × f(+) cel ... | 2010 | 20809290 |
| molecular basis of the supercoil deficit induced by the mini-f plasmid partition complex. | formation of a partition complex on plasmid f by binding of sopb protein to the sopc centromere is the first step in the partition process that ensures stability of f in dividing cells. establishment of the complex enables nonspecific binding of sopb to neighboring dna, which extends the partition complex and provokes reduction of negative supercoiling of the plasmid. this reduction is believed to reflect winding of dna into positive supercoils about sopb to create a nucleoprotein structure of p ... | 2009 | 19001378 |
| a plasmid rk2-based broad-host-range cloning vector useful for transfer of metagenomic libraries to a variety of bacterial species. | the majority of microorganisms in natural environments are difficult to cultivate, but their genes can be studied via metagenome libraries. to enhance the chances that these genes become expressed we here report the construction of a broad-host-range plasmid vector (prs44) for fosmid and bacterial artificial chromosome (bac) cloning. prs44 can be efficiently transferred to numerous hosts by conjugation. it replicates in such hosts via the plasmid rk2 origin of replication, while in escherichia c ... | 2009 | 19459950 |
| dual role of dna in regulating atp hydrolysis by the sopa partition protein. | in bacteria, mitotic stability of plasmids and many chromosomes depends on replicon-specific systems, which comprise a centromere, a centromere-binding protein and an atpase. dynamic self-assembly of the atpase appears to enable active partition of replicon copies into cell-halves, but for walker-box partition atpases the molecular mechanism is unknown. atpase activity appears to be essential for this process. dna and centromere-binding proteins are known to stimulate the atpase activity but mol ... | 2009 | 19740757 |
| f plasmid partition depends on interaction of sopa with non-specific dna. | bacterial atpases belonging to the para family assure partition of their replicons by forming dynamic assemblies which move replicon copies into the new cell-halves. the mechanism underlying partition is not understood for the walker-box atpase class, which includes most plasmid and all chromosomal paras. the atpases studied both polymerize and interact with non-specific dna in an atp-dependent manner. previous work showed that in vitro, polymerization of one such atpase, sopa of plasmid f, is i ... | 2008 | 18826408 |
| construction of a vibrio splendidus mutant lacking the metalloprotease gene vsm by use of a novel counterselectable suicide vector. | vibrio splendidus is a dominant culturable vibrio in seawater, and strains related to this species are also associated with mortality in a variety of marine animals. the determinants encoding the pathogenic properties of these strains are still poorly understood; however, the recent sequencing of the genome of v. splendidus lgp32, an oyster pathogen, provides an opportunity to decipher the basis of the virulence properties by disruption of candidate genes. we developed a novel suicide vector bas ... | 2007 | 17122399 |
| the incc korb region of rk2 repositions a mini-rk2 replicon in escherichia coli. | analysis by fluorescence microscopy has established that plasmid rk2 in escherichia coli and other gram-negative bacteria is present as discrete clusters that are located inside the nucleoid at the mid- or quarter-cell positions. a mini-rk2 replicon containing an array of teto repeats was visualized in e. coli cells that express a tetr-eyfp fusion protein. unlike intact rk2, the rk2 mini-replicon (pcv1) was localized as a cluster at the cell poles outside of the nucleoid. insertion of the o(b1)i ... | 2007 | 17521722 |
| polymerization of sopa partition atpase: regulation by dna binding and sopb. | in bacteria, mitotic stability of plasmids and many chromosomes depends on replicon-specific systems which comprise a centromere, a centromere-binding protein and an atpase. dynamic self-assembly of the atpase appears to enable active partition of replicon copies into cell-halves, but for most atpases (the walker-box type) the mechanism is unknown. also unknown is how the host cell contributes to partition. we have examined the effects of non-sequence-specific dna on in vitro self-assembly of th ... | 2007 | 17166176 |
| incp plasmids are most effective in mediating conjugation between escherichia coli and streptomycetes. | mobilizable shuttle plasmids containing the origin of transfer (orit) region of plasmid f (incfi), colib-p9 (inci1), and rp4/rp1 (incpalpha) were constructed to test the ability of the cognate conjugation system to mediate gene transfer from escherichia coli to streptomyces. the conjugative system of the incpalpha plasmids was shown to be most effective in conjugative transfer, giving peak values of (2.7 +/- 0.2) x 10(-2) s. lividans tk24 exconjugants per recipient cell. to assess whether the ma ... | 2006 | 16808239 |
| hydrodynamic plasmid dna gene therapy model in liver transplantation. | there is great interest in the field of transplantation to genetically modify grafts to decrease preservation injury or allograft rejection. although adenoviral gene transfer has been effective in experimental liver transplantation, viral toxicity and safety concerns limit potential use in clinical trials. therefore, the purpose of this study was to develop a model of nonviral gene transfer in the liver transplant setting, allowing for efficient transgene expression. | 2006 | 16926028 |
| inter- and intramolecular determinants of the specificity of single-stranded dna binding and cleavage by the f factor relaxase. | the trai protein of conjugative plasmid f factor binds and cleaves a single-stranded region of the plasmid prior to transfer to a recipient. trai36, an n-terminal trai fragment, binds ssdna with a subnanomolar k(d) and remarkable sequence specificity. the structure of the trai36 y16f variant bound to ssdna reveals specificity determinants, including a ssdna intramolecular 3 base interaction and two pockets within the protein's binding cleft that accommodate bases in a knob-into-hole fashion. mut ... | 2005 | 16216584 |
| crystallization of the c-terminal domain of the addiction antidote ccda in complex with its toxin ccdb. | ccda and ccdb are the antidote and toxin of the ccd addiction module of escherichia coli plasmid f. the ccda c-terminal domain (ccdac36; 36 amino acids) was crystallized in complex with ccdb (dimer of 2 x 101 amino acids) in three different crystal forms, two of which diffract to high resolution. form ii belongs to space group p2(1)2(1)2(1), with unit-cell parameters a = 37.6, b = 60.5, c = 83.8 a and diffracts to 1.8 a resolution. form iii belongs to space group p2(1), with unit-cell parameters ... | 2005 | 16511204 |
| plasmid distribution in european diaporthe helianthi isolates. | diaporthe helianthi is the causal agent of sunflower stem canker, a serious pathogen of sunflower in europe, which has been sporadically recorded in italy. a collection of 26 diaporthe helianthi isolates deriving from different geographic origins was analysed in order to determine the presence of extra-chromosomal genetic determinants and their molecular diversity. extra-chromosomal bands in total genomic dnas were identified in every french and the yugoslavian isolate and in only one italian is ... | 2005 | 15983747 |
| replication of a unit-copy plasmid f in the bacterial cell cycle: a replication rate function analysis. | for stability, the replication of unit-copy plasmids ought to occur by a highly controlled process. we have characterized the replication dynamics of a unit-copy plasmid f by a replication rate function defined as the probability per unit age interval of the cell cycle that a plasmid will initiate replication. analysis of baby-machine data [j. bacteriol. 170 (1988) 1380; j. bacteriol. 179 (1997) 1393] by stochastics that make no detailed reference to underlying mechanism revealed that this rate ... | 2004 | 15212889 |
| energetics of the sequence-specific binding of single-stranded dna by the f factor relaxase domain. | transfer of conjugative plasmids between bacteria requires the activity of relaxases or mobilization proteins. these proteins nick the plasmid in a site- and strand-specific manner prior to transfer of the cut strand from donor to recipient. trai36, the relaxase domain of trai from plasmid f factor, binds a single-stranded dna (ssdna) oligonucleotide containing an f factor sequence with high affinity and sequence specificity. to better understand the energetics of this interaction, we examined t ... | 2004 | 15123728 |
| the activity of a single-stranded promoter of plasmid colib-p9 depends on its secondary structure. | the leading region of the conjugal bacterial plasmid colib-p9 contains three dispersed repeats of a 328 bp sequence homologous to frpo, a sequence from plasmid f that acts as a promoter in single-stranded dna. one of these sequences, ssi3, inactive in the double-stranded form, promoted in vitro transcription exclusively from the single strand that is transferred during conjugation. promoter activity was dependent on the presence of rna polymerase holoenzyme containing sigma 70. transcription ini ... | 2004 | 15228523 |
| subdomain organization and catalytic residues of the f factor trai relaxase domain. | trai from conjugative plasmid f factor is both a "relaxase" that sequence-specifically binds and cleaves single-stranded dna (ssdna) and a helicase that unwinds the plasmid during transfer. using limited proteolysis of a trai fragment, we generated a 36-kda fragment (trai36) retaining trai ssdna binding specificity and relaxase activity but lacking the ssdna-dependent atpase activity of the helicase. further proteolytic digestion of trai36 generates stable n-terminal 26-kda (trai26) and c-termin ... | 2003 | 12637015 |
| crystallization and preliminary x-ray characterization of the relaxase domain of f factor trai. | conjugative plasmids are capable of transferring a copy of themselves in single-stranded form from donor to recipient bacteria. prior to transfer, one plasmid strand must be cleaved in a sequence-specific manner by a relaxase or mobilization protein. trai is the relaxase for the conjugative plasmid f factor. a 36 kda n-terminal fragment of trai possesses the single-stranded dna-binding and cleavage activity of the protein. crystals of the 36 kda trai fragment in native and selenomethionine-label ... | 2003 | 12876370 |
| non-cytotoxic variants of the kid protein that retain their auto-regulatory activity. | kid and kis are, respectively, the toxin and antitoxin encoded by the pard operon of plasmid r1. the recently solved crystal structure of kid has revealed that this protein closely resembles the ccdb toxin of plasmid f. in ccdb, the residues involved in toxicity are located at the carboxy-terminal end of the protein. however, an analogous information on the kid toxin was not available. here, we have characterized a collection of non-toxic mutants of the kid protein and identified the residues th ... | 2003 | 12932738 |
| the highly conserved tldd and tlde proteins of escherichia coli are involved in microcin b17 processing and in ccda degradation. | microcin b17 (mccb17) is a peptide antibiotic produced by escherichia coli strains carrying the pmccb17 plasmid. mccb17 is synthesized as a precursor containing an amino-terminal leader peptide that is cleaved during maturation. maturation requires the product of the chromosomal tlde (pmba) gene. mature microcin is exported across the cytoplasmic membrane by a dedicated abc transporter. in sensitive cells, mccb17 targets the essential topoisomerase ii dna gyrase. independently, tlde as well as t ... | 2002 | 12029038 |
| dna recognition by f factor trai36: highly sequence-specific binding of single-stranded dna. | the trai protein has two essential roles in transfer of conjugative plasmid f factor. as part of a complex of dna-binding proteins, trai introduces a site- and strand-specific nick at the plasmid origin of transfer (orit), cutting the dna strand that is transferred to the recipient cell. trai also acts as a helicase, presumably unwinding the plasmid strands prior to transfer. as an essential feature of its nicking activity, trai is capable of binding and cleaving single-stranded dna oligonucleot ... | 2001 | 11560509 |
| [the study of heterogeneity of plasmid-bearing and plasmid-f ree populations of bacillus subtilis under different environmental conditions]. | the population heterogeneity of recombinant and plasmid-free bacillus subtilis strains introduced into aquatic microcosms was studied. after introduction, the population of the plasmid-free strain b. subtilis 2335 in microcosms has long been represented by both vegetative cells and spores, whereas, already ten days after introduction, the population of the recombinant strain b. subtilis 2335/105 (km[symbol: see text]nf+) was represented only by spores. the number of plasmid copies in the spore i ... | 2000 | 10776630 |
| the plasmid f ompp protease, a homologue of ompt, as a potential obstacle to e. coli-based protein production. | ompt, an outer membrane-localized protease of escherichia coli, cleaves a number of exogenous and endogenous proteins during their purification. secy, an endogenous membrane protein, is a target of this artificial proteolysis in vitro. here we report that secy cleavage occurs even in cell extracts from ompt-disrupted cells, if they carry an f plasmid derivative. a gene, ompp, on the f plasmid was shown to be responsible for this proteolysis. these results indicate that the absence of an f-like p ... | 1999 | 10561486 |
| crystal structure of a prokaryotic replication initiator protein bound to dna at 2.6 a resolution. | the initiator protein (repe) of f factor, a plasmid involved in sexual conjugation in escherichia coli, has dual functions during the initiation of dna replication which are determined by whether it exists as a dimer or as a monomer. a repe monomer functions as a replication initiator, but a repe dimer functions as an autogenous repressor. we have solved the crystal structure of the repe monomer bound to an iteron dna sequence of the replication origin of plasmid f. the repe monomer consists of ... | 1999 | 10469640 |
| isolation and identification of fxsa, an escherichia coli gene that can suppress f exclusion of bacteriophage t7. | a selection for mutants of escherichia coli that survive coexpression of bacteriophage t7 gene 10 and plasmid f pifa has allowed the identification of a newly defined genetic locus, fxsa. fxsa is located at 94.1 min on the e. coli chromosome; the gene is monocistronic and non-essential for growth. overexpression of fxsa is necessary for resistance to the toxicity of t7 gene 10 in the presence of pifa; the original mutant strain contains a promoter-up mutation, changing a g residue to the "invari ... | 1999 | 10497016 |
| a putative lichenysin a synthetase operon in bacillus licheniformis: initial characterization. | certain bacillus licheniformis strains isolated from oil wells have been shown to produce a very effective biosurfactant, lichenysin a, which is structurally similar to another less active lipopeptide, surfactin. surfactin, like many small peptides in prokaryotes and lower eukaryotes, is synthesized non-ribosomally by multi-enzyme peptide synthetase complex. analysis of several peptide synthetases of bacterial and fungal origin has revealed a high degree of sequence conservation. two 35-mer olig ... | 1998 | 9765590 |
| escherichia coli coiv plasmid prk100: genetic organization, stability and conjugal transfer. | uropathogenic escherichia coli strains express chromosomal and plasmid-encoded virulence-associated factors such as specific adhesins, toxins and iron-uptake systems. a coiv plasmid (prk100) of a uropathogenic strain and its host ks533 were studied. the host strain encodes the k1 capsule, and p and s fimbriae, but neither haemolysin nor the cytotoxic-necrotic factor cnf1, indicating that this strain does not harbour a larger pathogenicity island. a restriction map of prk100 was constructed on th ... | 1998 | 9493372 |
| a hot spot in plasmid f for site-specific recombination mediated by tn21 integron integrase. | integron in2 integrase (inti1)-mediated site-specific recombination between two primary sites occurs at a high frequency, while that between a primary and a secondary site occurs at frequencies around 10,000 times lower. secondary sites consist of a pentanucleotide with only two fully conserved residues (gwtmw). the analysis of inti1-mediated recombinants in the plasmid pox38 revealed the existence in this plasmid of a site used at a frequency intermediate between those of primary and secondary ... | 1997 | 9209065 |
| plasmids isolated from marine sediment microbial communities contain replication and incompatibility regions unrelated to those of known plasmid groups. | two hundred ninety-seven bacteria carrying plasmids that range in size from 5 to 250 kb were identified from more than 1,000 aerobic heterotrophic bacteria isolated from coastal california marine sediments. while some isolates contained numerous (three to five) small (5- to 10-kb) plasmids, the majority of the natural isolates typically contained one large (40- to 100-kb) plasmid. by the method of plasmid isolation used in this study, the frequency of plasmid incidence ranged from 24 to 28% depe ... | 1997 | 9055407 |
| interaction of the icia protein with at-rich regions in plasmid replication origins. | a set of at-rich repeats is a common motif in prokaryotic replication origins. we have screened for proteins binding to the at-rich repeat region in plasmids f, r1 and psc101 using an electrophoretic mobility shift assay with pcr-amplified dna fragments from the origins. the icia protein, which is known to bind to the at-rich repeat region in the escherichia coli origin of chromosome replication, oric, was found to bind to the corresponding region from plasmids f (oris) and r1, but not to psc101 ... | 1996 | 8657567 |
| escherichia coli strains in which chromosome replication is controlled by a p1 or f replicon integrated into oric. | we report the construction of intp1 and intfs strains, in which the basic replicon from either plasmid p1 or plasmid f (oris) has been integrated in both orientations into the origin of replication, oric, of the escherichia coli chromosome. in these strains, oric is no longer functional and chromosome-replication is instead controlled by the integrated plasmid replicon. the strains were viable, showing that the deviation from normal chromosome-replication control was not large enough to prohibit ... | 1996 | 8809754 |
| random initiation of replication of plasmids p1 and f (oris) when integrated into the escherichia coli chromosome. | we have constructed intp1 and intfs strains of escherichia coli in which the basic replicons of either plasmid p1 or plasmid f (oris) were integrated into an inactivated oric, such that chromosome replication is controlled by the integrated plasmid replicon. in this study, we have further analysed these strains, and density-shift experiments revealed that chromosome replication occurred randomly during the cell cycle. flow-cytometry analyses of exponentially growing populations supported this co ... | 1996 | 8809755 |
| the tra region of the nopaline-type ti plasmid is a chimera with elements related to the transfer systems of rsf1010, rp4, and f. | the ti plasmids of agrobacterium tumefaciens encode two transfer systems. one mediates the translocation of the t-dna from the bacterium to a plant cell, while the other is responsible for the conjugal transfer of the entire ti plasmid from one bacterium to another. the determinants responsible for conjugal transfer map to two regions, tra and trb, of the nopaline-type ti plasmid ptic58. by using transposon mutagenesis with tn3hoho1, we localized the tra determinants to an 8.5-kb region that als ... | 1996 | 8763953 |
| bacteriophage mu repressor as a target for the escherichia coli atp-dependent clp protease. | bacteriophage mu repressor, which is stable in its wildtype form, can mutate to become sensitive to its escherichia coli host atp-dependent clpxp protease. we further investigated the determinants of the mutant repressor's sensitivity to clp. we show the crucial importance of a c-terminal, seven amino acid long sequence in which a single change is sufficient to decrease the rate of degradation of the protein. the sequence was fused at the c-terminal end of the ccdb and ccda proteins encoded by p ... | 1996 | 8617219 |
| a versatile low-copy-number cloning vector derived from plasmid f. | we have constructed a cloning vector based on plasmid mini-f for use in escherichia coli. plasmid pzc320 consists of the ori-2 replication unit of f that confers very low copy number (lcn), and includes the sop partition functions to insure stable plasmid maintenance in the absence of selection. a multiple cloning site (mcs) containing 16 unique restriction sites is located within the 5' end of the lacz alpha gene. expression of lacz alpha is under the control of the wild-type lactose operator/p ... | 1995 | 7590321 |
| purification and biochemical characterization of trwc, the helicase involved in plasmid r388 conjugal dna transfer. | trwc is an essential protein in conjugative dna transfer of the broad-host-range plasmid r388. trwc was purified in two chromatographic steps from trwc-overproducing bacteria. the purification procedure resulted in > 90% pure trwc protein, which was free of contaminating nuclease activities. trwc behaved as a dimer in gel-filtration chromatography in the presence of 550 mm nacl, and had a pi of 10.1. the purified protein showed in-vitro ssdna-dependent nucleoside-5'-triphosphatase and dna helica ... | 1994 | 8001558 |
| lon-dependent proteolysis of ccda is the key control for activation of ccdb in plasmid-free segregant bacteria. | the ccd locus contributes to the stability of plasmid f by post-segregational killing of plasmid-free bacteria. the ccdb gene product is a potent cell-killing protein and its activity is negatively regulated by the ccda protein. in this paper, we show that the ccda protein is unstable and that the degradation of ccda is dependent on the lon protease. differences in the stability of the killer ccdb protein and its antidote ccda are the key to post-segregational killing. because the half-life of a ... | 1994 | 8022284 |
| the product of the virb4 gene of agrobacterium tumefaciens promotes accumulation of virb3 protein. | the process of t-dna transfer from agrobacterium tumefaciens to plant cells is thought to involve passage of a dna-protein complex through a specialized structure in the bacterial membrane. the virb operon of a. tumefaciens encodes 11 proteins, of which 9 are known to be located in the membranes and 10 have been shown to be essential for virulence. sequence comparisons between proteins encoded by the virb operon and those encoded by operons from conjugative plasmids indicated that virb proteins ... | 1994 | 8071199 |
| genetic organization of the conjugal dna processing region of the incw plasmid r388. | the region of the incw plasmid r388 involved in conjugal dna metabolism and mobilization (mobw) has been analyzed by tn5tac1 insertion mutagenesis, genetic complementation and dna sequencing. three genes (trwa, trwb and trwc) were mapped within mobw. they are transcribed from the same strand and away from orit. the predicted products of trwa, trwb and trwc are proteins of 121, 507 and 966 amino acids, respectively. the three proteins were visualized in a minicell expression system, showing appar ... | 1994 | 8289274 |
| promiscuous dna transfer system of agrobacterium tumefaciens: role of the virb operon in sex pilus assembly and synthesis. | conjugative transfer of dna that occurs between bacteria also operates between bacteria and higher organisms. the transfer of dna between gram-negative bacteria requires initial contact by a sex pilus followed by dna traversing four membranes (donor plus recipient) using a transmembrane pore. accumulating evidence suggests that transfer of the t-dna from agrobacterium tumefaciens to plants may also occur via a conjugative mechanism. the virb operon of the ti plasmid exhibits close homologies to ... | 1994 | 7914664 |
| mutagenic and recombinagenic effects of diethylstilbestrol quinone. | estrogens are believed to be major contributors to many cancers of the human female genital tract, but the mechanism of their carcinogenic action is not well-understood. while a tumor-promoting role for estrogens is well-supported, whether they also act as tumor initiators has remained controversial. here, we have sought to examine the mutagenic potential of diethylstilbestrol, a synthetic estrogen that is a powerful carcinogen in hamsters, and is suspected to be a human carcinogen. phage m13 si ... | 1993 | 7690889 |
| the f plasmid ccdb protein induces efficient atp-dependent dna cleavage by gyrase. | dna topoisomerases perform essential roles in dna replication, gene transcription, and chromosome segregation. recently, we identified a new type of topoisomerase ii poison: the ccdb protein of plasmid f. when its action is not prevented by ccda protein, the ccdb protein is a potent cytotoxin. in this paper, using purified ccdb, ccda and gyrase, we show that ccdb protein efficiently traps gyrase in a cleavable complex. the ccda protein not only prevents the gyrase poisoning activity of ccdb but ... | 1993 | 8254658 |
| the tram protein of the conjugative plasmid f binds to the origin of transfer of the f and cole1 plasmids. | the gene encoding the tram protein of the conjugative plasmid f was cloned, overexpressed and the gene product was purified. the tram protein was found in the cytoplasm of cells carrying the f plasmid with a smaller amount in the inner membrane. dnase i footprinting experiments showed that the purified protein protects three regions in the f orit locus with different affinity for the upper and lower strands of dna. a 15-nucleotide motif was identified within the protected regions that represente ... | 1992 | 1479887 |
| cloning and stable maintenance of 300-kilobase-pair fragments of human dna in escherichia coli using an f-factor-based vector. | a bacterial cloning system for mapping and analysis of complex genomes has been developed. the bac system (for bacterial artificial chromosome) is based on escherichia coli and its single-copy plasmid f factor. it is capable of maintaining human genomic dna fragments of greater than 300 kilobase pairs. individual clones of human dna appear to be maintained with a high degree of structural stability in the host, even after 100 generations of serial growth. because of high cloning efficiency, easy ... | 1992 | 1528894 |
| sequence alterations affecting f plasmid transfer gene expression: a conjugation system dependent on transcription by the rna polymerase of phage t7. | we constructed derivatives of the escherichia coli conjugative plasmid f that carry altered sequences in place of the major transfer operon promoter, py. replacement of py with a promoter-deficient sequence resulted in a transfer-deficient, f-pilus-specific phage-resistant plasmid (pox38-tra701) that could still express traj and trat; tray, f-pilin, trad, and trai were not detectable on western blots. on a second plasmid (pox38-tra715) we replaced py with a phage t7 late promoter sequence. in ho ... | 1992 | 1479888 |
| site-specific proteolysis of mini-f plasmid replication protein repe destroys initiator function and generates an incompatibility substance. | plasmid f replication is controlled by a plasmid-specified rep protein with both autorepressor and initiator functions. the mechanism by which these two functions of a rep protein are balanced to achieve stable replication is unknown; however, we speculated in prior work that rep protein modification could be involved. we report here that naturally proteolyzed f repe protein has been detected and characterized. the processed molecule lost the first 17 n-terminal aminoacyl residues and initiator ... | 1992 | 1569028 |
| the rifampicin-inducible genes srnb from f and pnd from r483 are regulated by antisense rnas and mediate plasmid maintenance by killing of plasmid-free segregants. | the gene systems srnb of plasmid f and pnd of plasmid r483 were discovered because of their induction by rifampicin. induction caused membrane damage, rnase i influx, degradation of stable rna and, consequently, cell killing. we show here that the srnb and pnd systems mediate efficient stabilization of a mini-r1 test-plasmid. we also show that the killer genes srnb' and pnda are regulated by antisense rnas, and that the srnc- and pndb-encoded antisense rnas, denoted srnc- and pndb-rnas, are unst ... | 1991 | 1722558 |
| structural and functional comparison between the stability systems pard of plasmid r1 and ccd of plasmid f. | the stability determined by the systems pard of plasmid r1 and ccd of plasmid f is due to the concerted action of two proteins, a cytotoxin and an antagonist of this function. in this paper we report that ccda and kis proteins, the antagonists of the ccd and pard systems respectively, share significant sequence homologies at both ends. in kis, these regions seem to correspond to two different domains. despite the structural similarities, kis and ccda are not interchangeable. in addition we have ... | 1991 | 2017133 |
| host-parasite interactions: recent developments in the genetics of abortive phage infections. | recent progress towards the elucidation of the mechanisms of phage exclusion systems that lead to abortive infections is described. abortive infections constitute model systems for the study of host-parasite interactions, but until the 1980s such studies were confined largely to descriptions of a plethora of physiological dysfunctions. the use of cloning vectors containing the genes involved in the exclusion phenomena have helped to reduce the complexity of the abortive infection while maintaini ... | 1991 | 1831658 |
| expression of virulence and antibiotic resistance in an escherichia coli transconjugant carrying a large plasmid pcat120 of shigella dysenteriae type i and its spontaneous fragmentations. | the role of a 120-kb plasmid in relation to virulence and drug resistance factor in shigella dysenteriae was studied. for characterization of plasmids, the mating system is a useful and efficient means of transferring both large and small plasmids to a new host. the conjugative transfer of a 120-kb (pcat120) ampicillin-resistant plasmid of s. dysenteriae to e. coli k-12 was not successful. introduction of an e. coli fertility factor plasmid f, did not help to mobilize the plasmid. low transfer f ... | 1991 | 1823646 |
| the 41 carboxy-terminal residues of the minif plasmid ccda protein are sufficient to antagonize the killer activity of the ccdb protein. | the ccd operon of plasmid f encodes two genes, ccda and ccdb, which contribute to the high stability of the plasmid by post-segregational killing of plasmid-free bacteria. the ccdb protein is lethal to bacteria and the ccda protein is an antagonist of this lethal action. a 520 bp fragment containing the terminal part of the ccda gene and the entire ccdb gene of plasmid f was cloned downstream of the tac promoter. although the ccdb protein was expressed from this fragment, no killing of host bact ... | 1991 | 2034222 |
| genetic analysis of an invasion region by use of a tn3-lac transposon and identification of a second positive regulator gene, inve, for cell invasion of shigella sonnei: significant homology of inve with parb of plasmid p1. | we have previously cloned two distinct regions of the shigella sonnei form i plasmid pss120, a 37-kilobase-pair dna region and a virf region, which were found to be essential for cell invasion in escherichia coli k-12 (j. kato, k. ito, a. nakamura, and h. watanabe, infect. immun. 57:1391-1398, 1989). the 37-kilobase-pair dna region was randomly inserted by use of transposon tn3-lac. at least eight genes were found to be located within the region, as determined by analysis of tn3-lac-generated la ... | 1990 | 1688841 |
| escherichia coli minichromosomes: random segregation and absence of copy number control. | minichromosomes, i.e. plasmids that can replicate from an integrated oric, have been puzzling because of their high copy numbers compared to that of the chromosomal oric, their lack of incompatibility with the chromosome and their high loss frequencies. using single cell resistance to tetracycline or ampicillin as an indicator of copy number we followed the development of minichromosome distributions in escherichia coli cells transformed with minichromosomes and then allowed to grow towards the ... | 1990 | 2213882 |
| characterization of the f-plasmid conjugative transfer gene trau. | we characterized the trau gene of the escherichia coli k-12 conjugative plasmid f. plasmids carrying segments of the f transfer operon were tested for their capacity to complement f lac trau526. the protein products of trau+ clones were identified, and the nucleotide sequence of trau was determined. trau mapped between traw and trbc. it encodes a 330-amino-acid, mr36,786 polypeptide that is processed. ethanol caused accumulation of a precursor polypeptide; removal of ethanol permitted processing ... | 1990 | 2198250 |
| nucleotide sequence of the promoter-distal region of the tra operon of plasmid r100, including trai (dna helicase i) and trad genes. | the nucleotide sequence of the promoter-distal region of the tra operon of r100 was determined. there are five open reading frames in the region between trat and fino, and their protein products were identified. nucleotide sequences of plasmid f corresponding to the junction regions among the open reading frames seen in r100 were also determined. comparison of these nucleotide sequences revealed strong homology in the regions containing trad, trai and an open reading frame (named orfd). the trad ... | 1990 | 2164585 |
| the hok killer gene family in gram-negative bacteria. | the seven members of the hok killer gene family in gram-negative bacteria are described here. the members of this gene family have been sequenced and include hok/sok from plasmid r1, flm and srnb from plasmid f, pnd from plasmids r483 and r16, and gef and relf, which are located on the escherichia coli chromosome. the killer proteins encoded by these loci are highly toxic polypeptides of 50 to 52 amino acids. the proteins kill the cells from the inside by interfering with a vital function in the ... | 1990 | 2101633 |
| nucleotide sequence of the leading region adjacent to the origin of transfer on plasmid f and its conservation among conjugative plasmids. | the leading region of the escherichia coli k12 f plasmid is the first segment of dna to be transferred into the recipient cell during conjugal transfer. we report the nucleotide sequence of the 64.20-66.77f portion of the leading region immediately adjacent to the origin of transfer, orit. the 2582 bp region encodes three open reading frames, orf95, orf169 and orf273; the product of orf273, is equivalent in size and map location to the 35 kda protein, 6d, previously described (cram et al. 1984). ... | 1989 | 2693941 |
| the ssb gene of plasmid colib-p9. | the inci1 plasmid colib-p9 was found to carry a single-stranded dna-binding (ssb) protein gene (ssb) that maps about 11 kilobase pairs from the origin of transfer in the region transferred early during bacterial conjugation. the cloned gene was able to suppress the uv and temperature sensitivity of an ssb-1 strain of escherichia coli k-12. the nucleotide sequence of the colib ssb gene was determined, giving a predicted molecular weight of 19,110 for the ssb protein. sequence data show that colib ... | 1989 | 2651402 |
| control of the ccd operon in plasmid f. | the f sex factor plasmid of escherichia coli contains a pair of genes, ccda and ccdb, whose protein gene products are involved in an unusual feature of plasmid maintenance. the ccdb protein is a cytotoxin that becomes activated when the f plasmid is lost, thereby killing the f- segregant cells. in f+ cells, the ccda protein protects against the lethal effects of ccdb. in the present study we show that ccda and ccdb expressions are negatively autoregulated at the level of transcription. genetic s ... | 1989 | 2651399 |
| the f plasmid ccd autorepressor is a complex of ccda and ccdb proteins. | the ccd operon of plasmid f produces three proteins, ccda, ccdb, and repd. prior research has established that the operon is autorepressed and that at least ccdb, but not repd, is required for autorepression. a role for ccda in autorepression was suggested but not clearly shown. we now present a series of biochemical experiments which show that both ccda and ccdb proteins are required for maximal formation of protein-ccd operator complexes. we also show that ccda and ccdb are present in a comple ... | 1989 | 2615761 |
| location of enzymatic and dna-binding domains on e. coli protease la. | escherichia coli protease la is an atp-dependent enzyme that has a dna-binding site. the locations of the enzymatic and dna-binding sites are not known. we report that a 75-residue segment at the carboxy-terminus of the protease la is similar to part of bacillus licheniformis beta-lactamase, a serine enzyme. the comparison score is 8.2 standard deviations higher than that obtained with 10,000 comparisons of randomized sequences of these segments. the probability of obtaining such a score by chan ... | 1989 | 2647519 |
| participation of hup gene product in ori2-dependent replication of fertility plasmid f. | the fertility plasmid f'gal was not stably maintained in a hupa-hupb double mutant of escherichia coli. moreover, mini-f plasmids pfzy1, pftc1 and pftc2 were unable to transform the double mutant, though these plasmids efficiently transformed cells harboring a hupa or hupb single mutation. the composite plasmid pfhs1, which consists of the f5 dna fragment of f plasmid and the whole dna of a psc101 derivative that carries a temperature-sensitive mutation for dna replication, was not stably mainta ... | 1988 | 3063607 |
| aspects of plasmid f maintenance in escherichia coli. | a major class of replicons in procaryotes is typified by low copy number, nonrandom intracellular distribution, and stable inheritance. included in this class are chromosomes of gram-positive and gram-negative bacteria as well as a number of plasmids from these organisms. replicons in this major class have remarkable structural and functional similarities in the genes that effect and control replication. in the present work a review of plasmid f is presented as a paradigm for many aspects of thi ... | 1988 | 3052759 |
| identification and characterization of the products from the traj and tray genes of plasmid r100. | the nucleotide sequence of part of the tra region of r100 including traj and tray was determined, and the products of several tra genes were identified. the nucleotide sequence of traj, encoding a protein of 223 amino acids, showed poor homology with the corresponding segments of other plasmids related to r100, but the deduced amino acid sequences showed low but significant homology. the first four amino acids at the n-terminal region of the traj protein were not essential for positive regulatio ... | 1988 | 2836369 |
| analysis of escherichia coli k12 f factor transfer genes: traq, trba, and trbb. | the genes that encode the transfer properties of plasmid f, the fertility factor of escherichia coli k12, are known to be clustered over a large, 33.3-kb segment of f dna. as the central segment of the transfer region has not previously been well characterized, we constructed a detailed restriction map of the large f ecori dna fragment, fl, and isolated a series of plasmid derivatives that carry various overlapping segments of this f tra operon dna. we also analyzed the protein products of those ... | 1987 | 2827204 |
| repressor gene fino in plasmids r100 and f: constitutive transfer of plasmid f is caused by insertion of is3 into f fino. | fertility factor f confers bacterial conjugation, a process which involves at least 20 tra genes. resistance plasmids such as r100, r6-5, and r1 have homology with f in the tra region. conjugal transfer of these plasmids is, however, repressed, while transfer of f is constitutive. repression of r transfer is due to the existence of the two genes, called fino and finp; constitutive transfer of f is believed to be due to a lack of fino in f. in this paper, we report the identification and dna sequ ... | 1987 | 3027040 |
| stability and replication control of escherichia coli minichromosomes. | a stabilized minichromosome--a plasmid replicating from the chromosomal origin oric--was constructed by cloning the sopa,b,c, genes from plasmid f. this minichromosome had a loss frequency of less than 10(-3), while that of the nonstabilized parental plasmid was 2 x 10(-2) to 4 x 10(-2). both minichromosomes had the same average copy number per chromosomal origin, and the copy numbers were constant over an eightfold range of growth rates. different mutations in the mioc gene and promoter, from w ... | 1987 | 3294807 |
| expression of f transfer functions depends on the escherichia coli integration host factor. | we present evidence that the escherichia coli dna binding protein, ihf, plays an important role in conjugal transfer of the plasmid f. our results suggest that ihf exerts this effect by positively effecting transcription of the transfer (tra) operon of the plasmid. | 1987 | 3302598 |
| location of f plasmid transfer operon genes trac and traw and identification of the traw product. | as part of an analysis of the conjugative transfer genes associated with the expression of f pili by plasmid f, we have investigated the physical location of the trac and traw genes. we found that plasmid clones carrying a 2.95-kilobase ecori-ecorv f transfer operon fragment were able to complement transfer of f lac trac mutants and expressed an approximately 92,000-dalton product that comigrates with trac. we also found that traw-complementing activity was expressed from plasmids carrying a 900 ... | 1987 | 2889720 |
| integrative suppression of dnaa(ts) mutations mediated by plasmid f in escherichia coli is a dnaa-dependent process. | the thermosensitivity of dnaa(ts) mutations can be suppressed by integration of plasmid f (integrative suppression). in the light of the recent finding that f requires dnaa protein for both establishment and maintenance, integrative suppression of 11 dnaa(ts) mutations by a mini-f, pml31, integrated near oric was examined. the plating efficiency of integratively suppressed strains was dnaa(ts) allele-dependent and medium-dependent. the initiation capability of suppressed dnaa(ts) strains lacking ... | 1987 | 2830456 |
| the plasmid-maintenance functions of the p7 prophage. | the region responsible for the maintenance of the prophage of bacteriophage p7 as a stable, unit-copy plasmid was isolated in a lambda att vector which lysogenizes escherichia coli as a stable unit-copy plasmid under the control of the p7 replication origin. the p7 plasmid-maintenance region was shown to consist of adjacent replication and partition regions capable of functioning independently. the isolated replication region could support plasmid maintenance but the resulting plasmids were high ... | 1987 | 2827210 |
| [isolation and properties of recombinant dna from a plasmid and filamentous phage]. | in the course of studying extrachromosomal dna with composite replicons, a hybrid has been constructed by the in vitro recombination of the filamentous phage m13mp2 dna (rf) and plasmid pur222 (apr). both parental dnas contain a fragment of lac-operon (ca. 800 bp), which includes the distal end of laci gene, lacpo segments, and the lacz gene proximal region coding for 145 n-terminal amino acid residues of beta-galactosidase and thus providing for alpha-complementation, the effect being cancelled ... | 1986 | 3004511 |
| mini-f e protein: the carboxy-terminal end is essential for e gene repression and mini-f copy number control. | mini-f is a segment of the conjugative plasmid f consisting of two origins of replication flanked by regulatory regions, which ensure a normal control of replication and partitioning. adjacent to the ori-2 origin is a complex coding region that consists of the e gene overlapped by three open reading frames with the coding potential for 9000 mr polypeptides here designated 9 kd-1, 9 kd-2 and 9 kd-3. in this paper, we show that open reading frame 9 kd-3 is preceded by active promoter and shine-dal ... | 1986 | 3018261 |
| nucleotide sequences of the r1-19 plasmid transfer genes tram, finp, traj, and tray and the trayz promoter. | the complete nucleotide sequences of the r1 drd-19 (r1-19) plasmid transfer genes tram, finp, traj, and tray and the region encoding the trayz promoter were determined. the tram protein from r1-19 was similar to the 127-amino-acid tram product from the conjugative plasmid f; only 28 residues were not identical. finp, a negative regulatory element of the traj gene, contained a 12-base-pair inverted repeat identical to that found in the f plasmid, but differed in the 7 base pairs found between the ... | 1986 | 3009392 |
| polar mobilization of the escherichia coli chromosome by the cole1 transfer origin. | mobilization of the plasmid cole1 from cells containing a conjugative plasmid (such as f) requires the synthesis of cole1 mob proteins, and the presence, in cis, of bom (basis of mobility), a region of cole1 containing the origin of transfer (orit). the process of cole1 transfer is thought to resemble that of the conjugative plasmid f, although the plasmids share little sequence homology. in f, conjugation is preceded by a strand-specific nicking event at orit. the nicked strand is then conducte ... | 1986 | 3018432 |
| requirement of the escherichia coli dnaa gene product for plasmid f maintenance. | there are dnaa protein-binding sites in at least one f origin of replication, and only potentially leaky dnaa(ts) mutations had ever been used in previous studies indicating that f replication was independent of the dnaa gene product. here we show that an escherichia coli dnaa::tn10 host which does not make a dnaa gene product cannot sustain autonomous or integrated f plasmid maintenance. | 1986 | 3020005 |
| two functions of the e protein are key elements in the plasmid f replication control system. | by using a plasmid carrying a translational fusion between the e gene of the incfi plasmid f and the lacz gene, we located the operator of the autogenously regulated e gene to an inverted repeat overlapping the e-gene promoter and showing perfect homology to part of the sequence found in all the direct repeats of two regions exerting an inhibitory effect on f replication, incb and incc. excess e protein provided in trans to an f plasmid increased the replication frequency of the f plasmid. this ... | 1985 | 2999077 |
| promoters in the transfer region of plasmid f. | 1985 | 3893413 | |
| indirect sos induction is promoted by ultraviolet light-damaged minif and requires the minif lyna locus. | indirect prophage induction is produced by transfer to recipients of u.v.-damaged f plasmid (95 kb). we tested whether the sos signal can be produced by minif, a 9.3 kb restriction fragment, coding for the replication and segregation functions of plasmid f. we used lambda minif, a hybrid phage-plasmid. u.v.-irradiated lambda minif induced prophages phi 80 or lambda and sfia, a chromosomal sos gene, in more than 50% of the infected cells. the maximal inducing dose produced about 0.5 pyrimidine di ... | 1984 | 6096551 |
| stability of a plasmid f trim in populations of a recombination-deficient strain of escherichia coli in continuous culture. | populations of a reca derivative of escherichia coli ab1157 containing the plasmid f trim were grown in carbon-limited continuous culture at dilution rates of 0.1 h-1 to 0.4 h-1. the plasmid was lost after a lag, except in fermenter-experienced populations when it was retained. these results can be explained in terms of non-specific competition. | 1984 | 6380407 |
| identification of the minimal essential region for the replication origin of minif plasmid. | the minimal replication origin of minif plasmid was found to lie within a region of 217 bp in length. this region contains an at cluster and the four 19 bp direct repeats responsible for incompatibility, termed incb. its location coincides with hat of ori2 of plasmid f, previously inferred to be the replication starting point by electron microscopic analysis (eichenlaub et al. 1981). | 1984 | 6593565 |
| virus-plasmid interactions: mutants of bacteriophage t3 that abortively infect plasmid f-containing (f+) strains of escherichia coli. | bacteriophage t7 and many closely related phages abortively infect plasmid f-containing (f+) strains of escherichia coli. however phage t3, which is also closely related to t7, grows normally in f+ hosts. mutants of phage t3 that, like t7, are subject to f-mediated restriction have been isolated. these t3 mutants lack or are defective in one or both of two genes that are nonessential for phage growth in f-, wild-type strains. our results show that the products of phage t3 gene 1.1 or 1.2, or bot ... | 1984 | 6324192 |
| regulated expression of a gene important for replication of plasmid f in e. coli. | fusions between the gene encoding the e protein of the incfi plasmid f and the lac genes were constructed. analysis of the expression of beta-galactosidase from these fusions shows that the promoter for the e protein gene is located between the incb region and the structural gene for the e protein. near this promoter is a regulatory site on which a negative control element acts. most likely the e protein itself acts as a repressor of e gene expression and thus autoregulates its own expression. n ... | 1984 | 6325163 |