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

In this study we characterize a variant of the lambdacI857S7 prophage, designated lambdabi2cI857S7, which carries a DNA insertion. The insertion sequence is IS2, and it resides in the antipolar orientation II just upstream from the gene for prophage excision (xis) at 61.6%lambda. This bi2 insertion mutant could prove valuable for studies on possible recombination functions of IS2 DNA and of its effect on the lambda integration and excision functions.
Mol Gen Genet 1976 Aug 10
PMID:Insertion sequence IS2 near the gene for prophage lambda excision. 78 21

The bacterial mutation psuA1, known as (suA) a polarity suppressor, partially relieves all N defects in bacteriophage lambda growth. No evidence is found that psuA1 relieves Q defects in lambda growth. Specific mechanisms of action by the N and Q gene products are discussed. The psuA1 mutation was also found to suppress IS1 type but not IS2 type insertion mutations in lambda.
Mol Gen Genet 1976 Oct 18
PMID:Specificity of polarity suppression in E. coli: correction of defects in gene N, but not in gene Q, of phage lambda. 79 Jan 57

phi80dgal transducing bacteriophages have been isolated by the F-fusion technique of Press et al. (1971) and gal-operator-promoter insertion mutations have been introduced by homogenate formation. Five different phi80dgal isolates have been studied in more detail. One of the phi80 phages transduces the gal operon and gene aroG as well as at least part of the trp-operon; the gal operon of another phi80dgal transducing phage is inverted with respect to the phi80dgal sequences. Heteroduplex DNA mapping indicates that one of the phi80dgal isolates in addition to the gal operon and a portion of the adjacent chromosomal region carries an IS2-element which is derived from the F'gal episome. The isolated phi80dgal phages may be utilized for preparing pure gal mRNA and insertion-RNA as well as pure gal operon DNA.
Mol Gen Genet 1976 Oct 18
PMID:Isolation and characterization of phi80dgal transducing phages that carry gal operator-promoter insertion mutations. 79 83

A strain of E. coli carrying IS2 in the control region of the gal operon has been found to revert to a constitutive phenotype. These revertants can be divided into two classes, which differ in their rate of enzyme synthesis and gal transcription. One revertant synthesizes the gal messenger at a low level (low level revertants), the other at a higher level that exceeds that of the induced wild type two- to three-fold (high level revertants). In both cases it has been shown that the gal messenger is covalently bound to IS2-RNA, which is transcribed from IS2 in the original orientation. The evidence suggests, that the section of the IS2-element, from which this RNA is transcribed in the case of the high level revertants is smaller than 50 nucleotides long: i.e. the resolution of the hybridization method used for the detection of sequence homologies exceeds that of the electron microscopical heteroduplex technique.
Mol Gen Genet 1976 Dec 08
PMID:Gal mRNA initiated within IS2. 79 74

DNA of the IS-elements IS1 and IS2 was prepared by digestion of appropriate heteroduplex molecules with endonuclease S1, followed by sucrose gradient centrifugation or gel electrophoresis. The material obtained is homogeneous with regard to size. The length of IS1 DNA is 820 +/- 65 nucleotides, the length of IS2 DNA is 1,350 +/- 70 nucleotides. IS1 DNA is not cleaved by the restriction endonucleases Eco R1, Hind II or Hind III. IS2 DNA is cleaved once by each of the two latter enzymes. The buoyand density determined by equilibrium centrifugation of Hg-complexes in Cs2so4 corresponds to a GC content of approximately 50%. Labelling with polynucleotide kinase indicates that both IS DNA's have a guanosyl residue at both of their 5'-termini.
Mol Gen Genet 1976 May 07
PMID:The isolation of IS1 and IS2 DNA. 93 52

Lysyl-tRNA synthetases are synthesized in Escherichia coli from two distinct genes, lysS and lysU, which are regulated differentially. A strain which is null for lysS, the constitutive gene, was created by gene disruption (lysS1) and exhibited cold-sensitive lethality. Hence, lysS is dispensable at high temperatures. This cold sensitivity was suppressed by a multi-copy plasmid carrying lysU, the inducible gene. These data are interpreted as indicating that lysS is functionally replaceable by lysU for cell growth, and that the cold sensitivity of lysS1 is caused by insufficient expression of lysU at low temperatures. To investigate the mechanism of lysU expression, cold-resistant bypass mutations were isolated from lysS1, and named als (for abandonment of lysS). Two als mutations which were linked to lysU contain IS2 insertions upstream of the lysU promoter. They caused a 16-19-fold increase in the lysU-mRNA level. Furthermore, deletion mutations created immediately upstream of the lysU promoter restored growth of lysS1. These results suggest that transcription of lysU is negatively controlled by a cis-element located upstream of the promoter.
Mol Microbiol 1992 Jul
PMID:Differential regulation of two genes encoding lysyl-tRNA synthetases in Escherichia coli: lysU-constitutive mutations compensate for a lysS null mutation. 132 23

TraJ and SfrA are, respectively, plasmid and host (Escherichia coli)-encoded proteins normally required for F plasmid traY promoter function. Beginning with plasmids in which a traY-lacZ fusion gene, designated phi (traY'-'lacZ)hyb, and lacY are expressed from the F plasmid traY promoter, we isolated mutants in which lac gene expression was SfrA or TraJ-independent. A total of 45 of 50 SfrA-independent isolates obtained after 2-aminopurine mutagenesis proved to have chromosomal mutations, whereas four out of four isolates obtained without mutagenesis had plasmid mutations. All of 17 isolates selected for TraJ-independent expression after mutagenesis had plasmid mutations. By restriction endonuclease digestions, 25 of 26 SfrA-independent and TraJ-independent plasmid mutations were insertions. Four of the former and three of the latter were examined further. By sequence analysis, all seven proved to be IS1 or IS2 insertions defining five insertion sites between base-pairs -49 and -82 with respect to the major traY transcription initiation site. In two cases, the same insertion allele was obtained from the two selection schemes. All three of the mutants selected for TraJ-independent gene expression manifested SfrA-independent expression as well, and levels of beta-galactosidase in different plasmid mutant strains lacking TraJ and SfrA were indistinguishable. By primer extension analysis, transcription initiation sites for traY mRNA synthesis were unaltered by the mutations. Replacing the tra sequence upstream from base-pair -78, without genetic selection, increased beta-galactosidase activity in the absence of TraJ and SfrA greater than tenfold. Activity increased two- to threefold more in a traJ+ sfrA mutant strain, and fivefold more in a traJ+ sfrA+ strain. Activity was unaltered in an sfrA+ strain without TraJ. By primer extension analysis, the traY promoter was utilized under all conditions. The data indicate that regulation of traY promoter activity is strongly dependent on sequence context.
J Mol Biol 1991 Jul 20
PMID:Regulation of the F plasmid traY promoter in Escherichia coli K12 as a function of sequence context. 190 41

Escherichia coli K12 cells carrying a cloned 1.4 kb HindIII fragment from plasmid ColV2-K94, showed increased survival in guinea pig serum. The recombinant plasmid also conferred group II surface exclusion, i.e. the cells were reduced in recipient ability towards the incoming plasmid R538drd in conjugation experiments. Southern blotting suggested homology with bacteriophage lambda DNA and to the insertion element IS2. Determination of the DNA sequence of the fragment demonstrated the presence of a truncated IS2 (165 bp), separated by 250 bp from a 900 bp stretch of homology with lambda DNA, beginning within the Rz gene and continuing in the rightward direction on the lambda map. A 97 amino acid open reading frame (ORF) adjacent to Rz and on the opposite strand, remained intact in iss, with several amino acid changes. The ORF in iss is preceded by sequences resembling prokaryotic ribosome binding sites and promoters.
Mol Gen Genet 1989 Apr
PMID:Cloning and DNA sequence of plasmid determinant iss, coding for increased serum survival and surface exclusion, which has homology with lambda DNA. 254 40

The chromosome of an Escherichia coli K-12 strain W3110 contains seven copies of insertion element IS1, 12 copies of IS2 and six copies of IS3. We determined the approximate locations of six copies of IS1 (named is1A to is1F), ten copies of IS2 (named is2A to is2J), and five copies of IS3 (named is3A to is3E) on the W3110 chromosome by plaque hybridization using the "mini-set" of the lambda phage library that includes 476 clones carrying chromosomal segments that cover the W3110 chromosome almost entirely. Cleavage maps of the W3110 chromosome and cleavage analysis of phage DNAs carrying insertion elements allowed us to assign more precise locations to most of the insertion elements and to determine their orientations. Insertion elements were distributed randomly along the W3110 chromosome in one or other orientation. Several of these were located at the same positions on the chromosome of another E. coli K-12 strain, JE5519, and they were assumed to be the original complement of insertion elements in E. coli K-12 wild-type. Locations and orientations of such insertion elements were correlated well with Hfr points of origin and with crossover points for excision of some F' factors derived from several Hfrs. Insertion elements may be involved also in rearrangement of bacterial chromosomes.
J Mol Biol 1989 Aug 20
PMID:Mapping of insertion elements IS1, IS2 and IS3 on the Escherichia coli K-12 chromosome. Role of the insertion elements in formation of Hfrs and F' factors and in rearrangement of bacterial chromosomes. 255 81

Chromosomal DNA from 23 closely related, pathogenic strains of Escherichia coli was digested and probed for the insertion sequences IS1, IS2, IS4, IS5, and IS30. Under the assumption that elements residing in DNA restriction fragments of the same apparent length are identical by descent, parsimony analysis of these characters yielded a unique phylogenetic tree. This analysis not only distinguished among bacterial strains that were otherwise identical in their biochemical characteristics and enzyme electrophoretic mobilities, but certain aspects of the topology of the tree were consistent across several unrelated insertion elements. The distribution of IS elements was then reexamined in light of the inferred phylogenetic relationships to investigate the biological properties of the elements, such as rates of insertion and deletion, and to discover apparent recombinational events. The analysis shows that the pattern of distribution of insertion elements in the bacterial genome is sufficiently stable for epidemiological studies. Although the rate of recombination by conjugation has been postulated to be low, at least two such events appear to have taken place.
Mol Biol Evol 1989 Jan
PMID:Phylogenetic analysis using insertion sequence fingerprinting in Escherichia coli. 256 60


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