Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of eight different polA alleles on the replication of six different non-transferring enterobacterial plasmids have been tested. Using phage P1CM transduction, different allelic polA mutations were introduced into E. coli K12 strains carrying one of several antibiotic resistance plasmids. Plasmid stability in the transductants was examined by testing clones for drug resistance after growth under various conditions. From the results, the R factors may be divided into three different classes. One plasmid is only affected by PolA conditions which inhibit host cell growth, 3 plasmids (from the same compatibility group) are unstable under conditions in which the cells are severely deficient in DNA polymerase I and two other plasmids (compatible with each other and with the other 4) are immediately lost from such transductants and are unstable in a number of others. Furthermore, the plasmids which are most dependent on DNA polymerase I have been shown to replicate in the presence of chloramphenicol and therefore typigy a class of plasmids which includes bacteriocinogenic factors such as ColE1 and CloDF13, resistance determinant RSF1030 and the E. coli 15 minicircular plasmid.
Mol Gen Genet 1976 Feb 02
PMID:Effects of different alleles of the E. coli K12 pol A gene on the replication of non-transferring plasmids. 76 63

Strains of Escherichia coli K12 heterozygous for the R100-1 tetracycline resistance region were constructed. They carried the wild-type Tetr genes in the chromosome and single site Tets mutations on plasmids. Some heterozygotes could not express tetracycline resistance fully after induction. The mutant tet allele was thus partially dominant. When heterozygotes carrying the dominant tet mutant were plated on agar containing 20 mg/ml tetracycline, mutants which grew normally occurred at a frequency of 1-4 X 10(-4). Analysis of these dominance relief mutants showed that in 53/56 isolates the dominant tet allele was lost forming either Tra+ or Tra- deletion mutants of the plasmid. The mutation frequency was not affected either by the host chromosomal recA mutation or by the temperature of growth of the culture.
Mol Gen Genet 1976 Feb 02
PMID:R factor-mediated tetracycline resistance in Escherichia coli K12. Dominance of some tetracycline sensitive mutants and relief of dominance by deletion. 76 66

Infectivity of linear lambdaDNA molecules is proved to be about a hundred times higher in calcinated E. coli K12 (lambai434) than in E. coli K12(lambda-): the levels of transfection were 1-3-10(7) and 1-2-10(5) infective centers per 1 mug DNA, respectively. In E. coli JC 5743 rec B21 defective for exonucleases I and V the level of transfection was 1-3-10(6). High infectivity of linear lambdaDNA in lysogenic cells cannot be explained by a helping effect of phage particles spontaneously liberated by these cells. It can be caused by recombinations of inserted lambdaDNA molecules with prophage or by the low activity of some nucleases in the lysogenic cells. Covalently closed and "Hershey" ring forms of lambdaDNA penetrate the calcinated cells as readily as linear molecules do but the infectivity of the former ones is proved to be very low.
Mol Biol (Mosk)
PMID:[Infectivity of different forms of lambda bacteriophage DNA in transfection of calcinated Escherichia coli]. 76 69

Phi80dargECBH DNA has been used to direct cell-free synthesis of argininosuccinase, the argH gene product in Escherichia coli K12. In vitro enzyme synthesis is sensitive to repression by partially purified preparations from an argR+ strain but not by corresponding preparations from an argR- strain. Using DNA-cellulose chromatography, approximately seventyfold purification of repressor has been obtained. The partially purified preparation represses argininosuccinase synthesis but has no effect on beta-galactosidase synthesis.
Mol Gen Genet 1976 Feb 27
PMID:In vitro synthesis and repression of argininosuccinase in Escherichia coli K12; partial purification of the arginine repressor. 77 11

The transfecting activity of linear lambda DNA is 100 times higher in calcium treated E. coli K12 (lambda i434) than in non-lysogenic strains: the levels of transfection are 1-2.10(7) and 1-2.10(5) infective centers per 1 mug of lambda DNA respectively. The high efficiency of lysogenic cells transfection is not due to the spontaneously liberated "helper" phage. Evidently, it is called forth by transfecting DNA-prophage recombination or/and by inhibition of nuclease activity in lysogenic cells. Both ring forms lambda DNA (supercoiled and open circles) show very low infectivity, if any, in calcinated cells.
Mol Gen Genet 1976 Feb 27
PMID:Dependence of transfection efficiency of calcium treated Escherichia coli cells on bacterial genotype and form of Lambda DNA. 77 16

Plasmids of three different sizes, designated as plasmid A (mw: 65 X 10(6), plasmid B (mw: 41 X 10(6) and plasmid C (mw: 32 X 10(6) respectively, have been isolated from various hemolytic wild-type strains of E. coli. DNA-DNA hybridization was performed to determine their relationship. The wild-type strain, PM167a, harbours plasmids of all three sizes. Hybridization studies indicate that all three plasmids share extented sequence homologies but that plasmid A is not composed of plasmids B and C. Hybridization between plasmids of the donor strain and those of appropriate transconjugants demonstrates that in some cases plasmids with identical size are not longer completely homologous in their nucleotide sequences. This indicates that despite their defined sizes these plasmids are not stable genetic entities, but rather they undergo frequently recombination and dissociation during conjugation. In one particular transconjugant strain, K12-PM152/1, a plasmid D was found which is a stable recombined molecule of plasmids B and C of the original strain. Plasmids of size B found as the only extrachromosomal elements in a hemolytic wild-type strain (P224) and two transconjugant strains (e.g. K12-CM20 and K12-PM167/1) share extended nucleotide sequence homologies but are not identical. Little sequence homology was observed between two different hemolytic plasmids and the F and the Col Ib plasmids suggesting that the former do not belong to either the F-like or the I-like group of plasmids. Another hemolytic plasmid is F-like based on its sequence homologies with the F factor.
Mol Gen Genet 1976 Mar 22
PMID:Plasmids controlling synthesis of hemolysin in Escherichia coli. II. Polynucleotide sequence relationship among hemolytic plasmids. 77 90

An investigation of in vitro mutagenesis of plasmid DNA with hydroxylamine is described. The treated plasmid DNA was used to transform Escherichia coli K12. Mutants of the plasmid NTP3, which codes for resistance to ampicillin and sulphonamides, were isolated and characterised. They were classified according to the reduction in level of their beta-lactamase activity. Hydroxylamine-induced mutants of NTP14 were also isolated. This plasmid codes for ampicillin resistance, synthesis of colicin E1, and the EcoRI restriction and modification enzymes. One class of mutants is lethal to the host strain at temperatures above 33 degrees C, but carrier strains grow well at 28 degrees C. There is evidence that these mutants code for a temperature-sensitive EcoRI modification activity: the lethal effect probably results from the cleavage of the host-cell DNA by the restriction enzyme at non-permissive temperatures. The possible genetic uses of the mutant plasmids for the production of hybrid plasmids in the bacterial cell are discussed.
Mol Gen Genet 1976 Apr 23
PMID:Mutagenesis of plasmid DNA with hydroxylamine: isolation of mutants of multi-copy plasmids. 77 4

E. coli K12 transformants, selected as leu+ or pyrA+ transformants, were analysed for inheritance of some closely linked unselected markers. Based on the observation that the number of recombinants which require, besides an integration event, one or more crossing-over events was negligible, a simple mapping function was deduced. The function L= e-kd, which directly relates observed linkage of an unselected marker and the relative distance of that unselected marker to the selected marker, gave a consistent interpretation of the experimental results.
Mol Gen Genet 1976 Apr 23
PMID:Transformation in E. coli K12: relation of linkage to distance between markers. 77 5

Over sixty EMS induced mutations affecting gene lamB, presumably the structural gene for the lambda receptor in Escherichia coli K12, were examined for growth of lambda host range mutants and effect of nonsense suppressors. By the first criterion the mutations could be grouped in three classes. Bacteria with class I mutations allow growth of lambda mutants with extended host range (noted lambdah) of the type already described (Appleyard, MacGregor and Baird, 1956). Bacteria with class II mutations allow growth of lambdah mutants with still more extended host range (noted lambdahh). No host range mutants of lambda could be found which would grow on bacteria with class III mutations. Using nonsense suppressors it was found that class I and II consist of missense mutations, while class III consists of nonsense mutations. Exceptions are likely to exist (especially in class III) but were not found among the mutations tested. These observations are briefly discussed in terms of outer membrane protein integration and of phage receptor interaction.
Mol Gen Genet 1976 May 07
PMID:lamB mutations in E. coli K12: growth of lambda host range mutants and effect of nonsense suppressors. 77 86

Approximately 6% of Escherichia coli K12 (lambda wild-type) cells whose prophage was induced by treatment with N-methyl-N-nitrosourea initiated plaques on E. coli K12S which contained wholly or mostly clear plaque-forming mutants (lambdac). "Fuzzy" plaque-forming mutants (lambdaf) were also recognised, at lesser frequencies. Less marked mutation occurred during prophage induction by N-ethyl-N-nitrosourea, and no apparent mutation occurred during induction by methyl and iso-propyl methanesulphonates, or by a non-inducing treatment of the lysogen with ethyl methanesulphonate. Mutagenic effects of treatment of susceptible host cells or of phage alone, prior to infection, seem not to account for the phenomenon described.
Mol Gen Genet 1976 May 07
PMID:Mutation of lambda during prophage induction by nitrosamides. 77 87


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