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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cloned Citrobacter freundii ampC beta-lactamase is inducible in the presence of its regulatory gene ampR in Escherichia coli (Lindberg et al., 1985). The basal level of expression and inducibility are affected by two E. coli proteins encoded by the closely linked ampD and ampE genes. Deletion of both genes led to constitutive ampR-dependent overproduction of beta-lactamase, whereas an out-of-frame deletion in AmpD caused the basal expression to increase two-fold. This ampD1 mutant was inducible at lower beta-lactam concentrations than the wild type. An IS1 insertion in ampD was polar on ampE expression and increased basal beta-lactamase expression 30-fold while mediating a semi-constitutive phenotype. AmpE expressed from a recombinant plasmid in an ampD-ampE deletion mutant reduced basal beta-lactamase expression to wild-type levels but did not markedly reduce beta-lactam resistance since the cells became hyperinducible. In the absence of AmpD, increasing levels of AmpE therefore decrease the basal expression of AmpC beta-lactamase in an AmpR-dependent manner. AmpD modulated the response exerted on beta-lactamase expression by AmpE. The ampD gene encodes a 20.5kD cytoplasmic protein while the 32.1kD ampE gene product is an integral membrane protein with a likely ATP-binding site between the second and third putative transmembrane region. Since neither AmpD nor AmpE are needed for beta-lactam induction and since these proteins could not be covalently labelled by benzylpenicillin, they are not thought to act as beta-lactam-binding sensory transducers. Instead it is suggested that AmpD and AmpE sense the effect of beta-lactam action on peptidoglycan biosynthesis and relay this signal to AmpR.
Mol Microbiol 1989 Aug
PMID:Signalling proteins in enterobacterial AmpC beta-lactamase regulation. 269 40

We report here that the ends of IS1 are bound and protected in vitro by the heterodimeric protein integration host factor (IHF). Under identical conditions, RNA polymerase binds to one of these ends (IRL) and protects a region that includes the sequences protected by IHF. Other potential sites within IS1, identified by their homology to the apparent consensus sequence, are not protected. Footprinting analysis of deletion derivatives of the ends demonstrates a correspondence between the ability of the end sequence to bind IHF and its ability to function as an end in transposition. Nonetheless, some transposition occurs in IHF- cells, indicating that IHF is not an essential component of the transposition apparatus. IHF also binds and protects four closely spaced regions within the major hot-spot for insertion of IS1 in the plasmid pBR322. This striking correlation of hot-spot and IHF-binding sites suggests a possible role for IHF in IS1 insertion specificity.
J Mol Biol 1987 May 20
PMID:Escherichia coli integration host factor binds specifically to the ends of the insertion sequence IS1 and to its major insertion hot-spot in pBR322. 282 Dec 73

Shigella sonnei contains repetitive sequences, including an insertion element IS1, which can be isolated as double-stranded DNA fragments by DNA denaturation and renaturation and by treatment with S1 nuclease. In this paper, we describe a method of cloning the IS1 fragments prepared by the S1 nuclease digestion technique into phage M13mp8 RFI DNA. Several clones contained IS1, usually with a few additional bases. We isolated and characterized five other repetitive sequences using this method. One sequence, 1264 base-pairs in length, had terminal inverted repeats and contained two open reading frames. This sequence, called IS600, showed about 44% sequence homology with IS3 and was repeated more than 20 times in the Sh. sonnei chromosome. Another sequence (named IS629, 1310 base-pairs in length), which was repeated six times, was found also to be related to IS3 and thus IS600. Two other sequences (named IS630 and IS640, 1159 and 1092 base-pairs in length, respectively), which were repeated approximately ten times, had characteristic terminal inverted repeats and contained a large open reading frame coding for a protein. The inverted repeat sequences of IS630 were similar to the sequence at one end of IS200, a Salmonella-specific IS element. The fifth sequence, repeated ten times in Sh. sonnei, had about 98% sequence homology with a portion of IS2. The method described here can be applied to the isolation of IS or iso-IS elements present in any other bacterial chromosome.
J Mol Biol 1987 Aug 05
PMID:Isolation and characterization of IS elements repeated in the bacterial chromosome. 282 81

The properties of IS1/Tn9'-mediated cointegrates between plasmids pDK57 (pBR322:: :: Tn9') and pRP3.1--the deletion derivative of RP1 were investigated. It was found that IS1/Tn9'-mediated integration of pDK57 into the active transcribed regions of pRP3.1 (in particular kan and tet genes) leads to formation of unstable cointegrates capable of resolving in E. coli K-12 rec+ and recA cells. The structure of dissociation products of unstable cointegrates was studied. According to the data received in rec+ cells, the unstable cointegrates mainly produced plasmids pDK57 and pBR322::IS1--Cms-derivative of pDK57 as resolution products. In recA cells the cointegrates dissociate in different ways, and this process leads to the formation of not only pDK57 and pBR322::IS1, but also to the production of the deletion derivatives of these plasmids as well as to the derivatives of pDK57 and pBR322::IS1, containing duplications of IS1 or separate parts of Tn9'. It was concluded that the IS1-specific recombinase is involved in the dissociation (resolution) of unstable IS1/Tn9'-mediated cointegrates. This recombinase recognizes the sites localized in both inverted termini of IS1 as well as in the adjacent DNA segments. Hence, it is possible, that the IS1 recombinase is involved also in the generation of IS1-adjacent delations.
Mol Biol (Mosk)
PMID:[Dissociation of unstable cointegrate plasmids formed during transposition of IS1 element: the role of IS1 encoded recombinase]. 282 86

The plasmid pNT6 permits selection of IS1-element insertions into the plasmid occurring with the frequency about 10%. The bacteriophage promoter pL cloned in pNT6 is a hot-spot region for IS1-element insertion. The frequency of IS1 transposition into pL depends on genotype. The plasmid pNT6 may be considered to be a useful target DNA for screening and analysis of IS1-element transposition.
Mol Gen Mikrobiol Virusol 1987 Sep
PMID:[Effective selection and analysis of IS1 element transposition using the oLpLN region of phage lambda]. 282 39

To learn more about the ways in which genes silenced by insertion mutations can be reactivated, we have undertaken a systematic investigation of Gal+ revertants of the polar mutant galOP-306::IS1 in Escherichia coli K12. The selective conditions used excluded reversion to wild type by precise excision of IS1. In this system (which resided on a multi-copy plasmid) reversion to the Gal+ phenotype occurred with a frequency of about 10(-7) per cell and per generation. Analysis of the revertants revealed that - with the single exception of the previously published chromosomal mutant sis1 - alterations in the structure of IS1 lead to reactivation of gal operon expression. These events fall into four classes: (I) insertion of IS2 at position 327 in IS1, insertion of IS2 at position 687 in IS1, (III) insertion of a hitherto undetected mobile element, IS150, at position 387, (IV) a 16-bp deletion encompassing IS1 coordinates 553-568. Of some 200 independent reversion events studied, all but one were of types I-III i.e. they involved the intervention of a second mobile element.
Mol Gen Genet 1988 Feb
PMID:Second-element turn-on of gene expression in an IS1 insertion mutant. 283 4

Genes determining the high affinity iron transport system mediated by the siderophore aerobactin are flanked in the enterobacterial plasmid pColV-K30 by inverted repeats of IS1 sequences, suggesting that the aerobactin genes are part of a transposon. To study this possibility, the entire region between the two IS1 sequences was cloned as an 18 kb HindIII-BamHI restriction fragment in pUC8 giving plasmid pMO1. A number of derivatives of pMO1, in which aerobactin genes were tagged with a kanamycin resistance gene, were prepared in order to assess the ability of both IS1s to promote the formation of cointegrates with pCJ105, an F derivative devoid of insertion sequences. Mating-out assays indicated that both flanking IS1s were active in cointegrate formation at detectable frequencies. In some cases, the cointegrates could be resolved, the final result being a transposition-like event for the entire aerobactin system.
Mol Gen Genet 1988 Aug
PMID:IS1-mediated mobility of the aerobactin system of pColV-K30 in Escherichia coli. 284 8

Transposon Tn2555 was isolated from a clinical E. coli strain carries the genes for sucrose utilization. Previously it was shown that Tn2555 is very unstable and undergoes structural rearrangements with a high frequency. Several deletion derivatives of Tn2555 and one with an inversion of the internal segment were found. They form the Tn2555 transposon family. This paper describes further structural and functional analysis of Tn2555. In the course of the experiments on pBR325 (Mob-) mobilization by conjugative RP4 derivatives, containing Tn2555 family elements, it was found, that all of them induce cointegrate formation. Some of these cointegrates were able to dissociate in rec+ and recA E. coli cells. Restriction endonuclease analysis of the resulting plasmids have shown, that among them were the end products of the Tn2555 transposition from RP4 to pBR325. Besides, the pBR325 derivatives, containing a discrete DNA segment of approximately 800 b.p., originating from Tn2555, were found. The segment can transpose from pBR325 to RP4 indicating that it is an insertion sequence. This new IS-element was designated IS286. The size and the genetic properties of IS286 resemble those of the IS1 element. However restriction analysis and Southern hybridization data show no significant homology between IS286 and IS1. It was found that the Tn2555 family elements are flanked by directly repeated IS286. One of them (Tn2555.3) contains an additional copy of IS286 in its internal region.
Mol Biol (Mosk)
PMID:[Structural and functional organization of the transposon Tn2555 carrying saccharose utilization genes]. 284 16

We present a method that allows positive selection and rapid analysis of mutations in Enterobacteriaceae. Mutations are detected in a 2630 bp selection cartridge inserted in two different bacterial multicopy plasmid vectors. Spontaneous mutations in Escherichia coli, Enterobacter cloacae and Citrobacter freundii include insertions, deletions and point mutations. The small size of the target sequence facilitates rapid analysis of DNA rearrangements by cleavage with restriction enzymes and of any type of mutation by DNA sequence analysis. While in E. coli insertions of the mobile elements IS1, IS2 and IS5 were readily found, insertions of putative new transposable elements were detected in Enterobacter cloacae. The selection cartridge can thus serve as a tool for studying the spectrum of insertion mutations in Enterobacteriaceae and probably other Gram-negative bacteria, and the dependency of this spectrum on physiological and environmental factors and the host's genetic background can be investigated.
Mol Gen Genet 1988 Dec
PMID:A selection cartridge for rapid detection and analysis of spontaneous mutations including insertions of transposable elements in Enterobacteriaceae. 285 30

The insertion of IS1 elements into lacZ results in the loss of beta-galactosidase activity, and such insertions exert a severe polar effect on the expression of the distal genes of the operon. In addition to these properties, the mutation lacZ::IS1-MS319 has the unique property of reversion to Lac+ (ts) spontaneously or after treatment with the frameshift mutagen ICR-191; such revertants retain the IS1 element. We have determined that the site of integration of IS1 into lacZ is at position 4338, 18 nucleotides from the end of the sequence encoding the C-terminus of beta-galactosidase. Reversion to Lac+ promoted by ICR-191 results from the loss of a G residue from a GGG sequence located at the junction of lacZ and IS1. As a result an active, but temperature-sensitive, lacZ-IS1 fusion protein is formed containing six amino acids derived from IS1 which replace six amino acids encoded by lacZ. The IS1 element in MS319 is a new member of the iso-IS1 family, which we designate IS1T.
J Mol Biol 1985 Feb 20
PMID:A frameshift mutation at the junction of an IS1 insertion within lacZ restores beta-galactosidase activity via formation of an active lacZ-IS1 fusion protein. 298 6


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