Topic
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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TL;DR: It is demonstrated that RNA polymerase bound at the PR promoter of bacteriophage lambda can repress transcription initiation from the divergently transcribed PRM promoter in vitro, and the possibility that an additional mechanism could be operative, whereby lambda repressor indirectly activates PRM transcription by excludingRNA polymerase from the PRPromoter.
30 citations
TL;DR: The cheA-cheB region in E. coli is complex and produces at least three gene products, which are suggested to be the same as the methyl-accepting chemotaxis protein described by Kort et al.
Abstract: Molecular cloning techniques were used to construct hybrid Escherichia coli lambda phage and isolate Col E1 factors that carried the cheB region of the E coli genome The products of these genes were examined by using a series of deletions in the phage to stimulate specific polypeptide synthesis in ultraviolet-irradiated cells and by using Col factor to program protein synthesis in minicells Seven flagellar related polypeptides were synthesized Three of these with apparent molecular weights of 38,000, 28,000, and 8,000 were associated with the cheB region; three polypeptides 63,000, 61,000, and 60,000 were associated with the region that maps between cheB and cheA These bands were referred to as the triplet group We suggest that these polypeptides are the same as the methyl-accepting chemotaxis protein described by Kort et al (Proc Natl Acad Sci USA 72:3939-3943, 1975) Another polypeptide with a molecular weight of 12,000 is associated with the cheA region which also produces at least three gene products We conclude that the cheA-cheB region in E coli is complex Further genetic and biochemical analyses are required to describe all of these products
30 citations
TL;DR: The ratio of effector to inhibitor was much higher in P22 than in lambda and it is proposed that this reflects less transcriptional readthrough at the late terminator t(R) and suggests that the dual-start motif in genes 13 and S may be important for establishment of maintenance of the lysogenic state.
Abstract: Gene 13 of bacteriophage P22 is functionally equivalent to lambda lysis gene S. Gene S codes for two products, the polypeptides S105 and S107, produced from translational initiation events at the third and first codon, respectively. We have shown that the two polypeptides have opposing functions in lysis: S105 is the lethal lysis effector, and S107 acts as an inhibitor of lysis (U. Blasi, K. Nam, D. Hartz, L. Gold, and R. Young, EMBO J. 11:3501-3510, 1989). Gene 13 has a 108-codon reading frame and its product begins with a similar motif: Met-1-Lys-2-Lys-3-Met-4. Here, we present in vivo and in vitro evidence for the expression of a 13(108) and a 13(105) product and show that the lambda lysis control mechanisms is evolutionarily conserved in phage P22. In this case 13(108), like S107 in lambda, functions as the inhibitor of the lysis effector 13(105). Although the DNA sequences upstream of the S and 13 gene starts showed less homology, the same structural characteristics, i.e., stem-loop structures immediately upstream and about 10 codons downstream of the start region, were present in both reading frames. Using in vitro mutagenesis and toeprinting, we show that the upstream stem-loop structures of genes 13 and S, containing the Shine-Dalgarno sequence for initiations at Met-1, are interchangeable. Moreover, our data indicate that the stability of the secondary structures present in the translational initiation regions of genes S and 13 is set to create a particular ratio of initiation events at Met-1 and Met-3 or Met-4. The ratio of effector to inhibitor was much higher in P22 than in lambda. We propose that this reflects less transcriptional readthrough at the late terminator t(R) and suggests that the dual-start motif in genes 13 and S may be important for establishment of maintenance of the lysogenic state.
30 citations
TL;DR: In UV-irradiated phage WR was reduced, but not eliminated, in the uvrE mutant, and WM was entirely suppressed, another example of uncoupling of WR and WM which shows that several repair systems are active in WR but only some of them are mutagenic.
Abstract: UV irradiation of Escherichia coli wild-type cells manifested the phenomena of W-reactivation (WR) and W-mutagenesis (WM) of phage lambda irradiated by 60Co gamma-rays in broth. WR of gamma-irradiated phage was half as efficient as that of UV-irradiated phage, although the frequency of c mutations in conditions of WR was about the same in both phages. The xthA and recBrecC sbcB mutants were practically identical with wild-type cells in respect of WR and WM of UV- and gamma-irradiated phage. As in UV-irradiated phage, WR and WM of gamma-irradiated phage were absolutely dependent on the recA+ and lexA+ genes of the host cell. WR and WM required much smaller doses of UV radiation for induction in polA1 and uvrB mutants. The lig-ts mutant, temperature sensitive in polynucleotide ligase, was deficient in WR and WM of UV- and gamma-irradiated phage at the semi-permissive temperature of 37 degrees. The uvrE502 mutant and the allelic recL152 strain were absolutely deficient in WR and WM of gamma-irradiated phage. In UV-irradiated phage WR was reduced, but not eliminated, in the uvrE mutant, and WM was entirely suppressed. This is another example of uncoupling of WR and WM which shows that several repair systems are active in WR but only some of them are mutagenic.
30 citations
TL;DR: It is hypothesized that by sensing the low environmental temperature the PL promoter plays a role in determining the direction of phage λ development and can lysogenize efficiently but cannot complete the lytic cycle.
Abstract: We found that the activity of the phage λ PL promoter is inversely dependent on temperature. Both in vivo and in vitro transcription assays revealed that the rather unique temperature response of PL is a sum of an intrinsic property of the promoter and its activation by integration host factor. We also found that at low temperature, phage λ can lysogenize efficiently but cannot complete the lytic cycle. We hypothesize that by sensing the low environmental temperature the PL promoter plays a role in determining the direction of phage λ development.
30 citations