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Lambda phage

About: Lambda phage is a research topic. Over the lifetime, 1609 publications have been published within this topic receiving 84675 citations. The topic is also known as: Enterobacteria phage lambda.


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Journal ArticleDOI
TL;DR: The non‐lambdoid coliphage 186 is proposed to be regulated by a novel mechanism in which a CI octamer bound at pR forms alternative DNA loops to pL or to a flanking site, depending on CI concentration.
Abstract: The non-lambdoid coliphage 186 provides an alternative model to the lytic-lysogenic switch of phage lambda. Like lambda, the key switch regulator, the CI repressor, associates to octamers. Unlike lambda, the lytic promoter (pR) and the lysogenic promoter (pL) are face-to-face, 62 bp apart and are flanked by distal CI binding sites (FL and FR) located approximately 300 bp away. Using reporter and footprinting studies, we show that the outcome, but not the mechanism, of regulation by 186 CI is very similar to lambda. 186 CI stimulates pL transcription indirectly by repressing convergent interfering transcription from pR. However, in the absence of the flanking FL and FR sites, CI bound at pR interacts co-operatively with a weak CI binding site at pL and represses both promoters. FL and FR play a critical role; they assist repression of pR and simultaneously alleviate repression of pL, thus allowing high pL activity. We propose that the 186 switch is regulated by a novel mechanism in which a CI octamer bound at pR forms alternative DNA loops to pL or to a flanking site, depending on CI concentration.

51 citations

Journal ArticleDOI
TL;DR: In this article, a 10.9-kilobase EcoRI fragment of deoxyribonucleic acid derived from the leu transducing phage lambda G4 was used to investigate whether leu genes are part of a single operon or constitute separate but adjacent operons controlled from a common site.
Abstract: The ilvHI and leu genes of Escherichia coli K-12 are contained on a single 10.9-kilobase EcoRI fragment of deoxyribonucleic acid derived from the leu transducing phage lambda G4. Since the expression of all of these genes is controlled by leucine, we investigated whether they are part of single operon or whether they constitute separate but adjacent operons controlled from a common site. Both cloning and hybridization studies indicated that ilvHI and leu are distinct operons. They are transcribed in opposite directions and are separated by approximately 1,500 base pairs of deoxyribonucleic acid. Hybridization experiments showed that the expression of ilvHI is regulated chiefly at the level of transcription. The size of the ilvHI messenger ribonucleic acid is estimated to be 2,550 bases.

51 citations

Journal ArticleDOI
TL;DR: Escherichia coli K12 cells carrying a cloned 1.4 kb HindIII fragment from plasmid ColV2-K94, showed increased survival in guinea pig serum and southern blotting suggested homology with bacteriophage lambda DNA and to the insertion element IS2.
Abstract: 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.

51 citations

Journal ArticleDOI
01 Jan 1987-Gene
TL;DR: In analysis of the cloned trp regulatory region, the λ phage system faithfully reproduced the tight regulation by tryptophan characteristic to the natural trp operon on the E. coli chromosome, whereas the plasmid counterpart exhibited a substantially relaxed response.

50 citations

Journal ArticleDOI
TL;DR: The receptor for phage lambda in Escherichia coli was isolated by cholate extraction and purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and found that the pore characteristics were similar to those exhibited by the matrix protein (porin) and the lambda receptor showed a somewhat higher degree of cation specificity.
Abstract: The receptor for phage lambda in Escherichia coli was isolated by cholate extraction and purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Protein bands corresponding to the monomer and the dimer were eluted from the gel and tested for their activity to inactivate phage lambda and to form pores in black lipid membranes. It was found that only the dimer inactivated phage lambda, whereas both the monomer and the dimer were active in forming pores. The pore characteristics were similar to those exhibited by the matrix protein (porin) (R. Benz, K. Janko, W. Boos, and P. Lauger, Biochim. Biophys. Acta 511:305--319, 1978). In comparison, the lambda receptor showed a somewhat higher degree of cation specificity, and its pore size was larger. Assuming that the thickness of the outer membrane is 7.5 nm and that the pore is an ideal hydrophilic channel, the pore diameter in vivo was estimated to be 1.6 nm for the lambda receptor and 1.2 nm for the matrix protein.

50 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20226
20219
20209
20195
20188
20177