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.

A minor arginine tRNA mutant limits translation preferentially of a protein dependent on the cognate codon.

Abstract: The Escherichia coli argU gene encodes a rare arginine tRNA (anticodon UCU) that translates the similarly rare AGA codon. The argU10(Ts) mutation is a transition that changes the first nucleotide of the mature tRNA from G to A, presumably destabilizing the acceptor stem. This mutation, when present in haploid condition in the chromosome, reduces the growth rate at 30 degrees C and results in cessation of growth after 60 to 90 min at 43 degrees C. The mutation also preferentially limits (compared with total protein synthesis) translation of an induced gene that depends on five AGA codons, i.e., the lambda cI repressor gene. Translation of another inducible protein, beta-galactosidase, which does not involve AGA codons, was inhibited to a much lesser extent. The chromosomal argU(Ts) mutation also confers the Pin phenotype, that is, loss of ability of the host, as a P2 lysogen, to inhibit growth of bacteriophage lambda, probably the result of reduced translation of the P2 old gene, which contains five AGA codons (E. Haggard-Ljungquist, V. Barreiro, R. Calendar, D. M. Kurnit, and H. Cheng, Gene 85:25-33, 1989).

Phage lambda receptor (lamB protein) in Escherichia coli.

Abstract: The main properties of the lambda receptor are summarized in the table. Because these can be studied by a combination of genetic, biophysical, and biochemical techniques, the lambda receptor now appears to represent one of the best systems for study of structure-function relationships in a membrane protein. In addition, as explained in this volume, it also constitutes a good system for study of the export of proteins to extracytoplasmic locations.

Bleomycin-induced mutagenesis in repackaged lambda phage: base substitution hotspots at the sequence C-G-C-C

Abstract: DNA isolated from lambda phage was treated with bleomycin A2 plus Fe2+ The bleomycin-damaged DNA was added to lambda packaging extracts and the resulting phage were grown in SOS-induced E coli Under these conditions, treatment of the DNA with 08 microM bleomycin reduced the viability of the repackaged phage to 3% and increased the frequency of clear-plaque mutants in the progeny by a factor of 16 Bleomycin-induced mutations which mapped to the DNA-binding domain of the cI gene were subjected to DNA-sequence analysis The most frequent events were single-base substitutions at G:C base pairs, nearly all of which occurred at cytosines in the sequence Py-G-C Cytosines in the third position of the sequence C-G-C-C were particularly susceptible to mutation At A:T base pairs, mutations were less frequent and were a mixture of single-base substitutions and -1 frameshifts, occurring primarily at G-T and A-T sequences Thus, the overall specificity of bleomycin-induced mutations matches that of bleomycin-induced DNA lesions (strand breaks and apyrimidinic sites), which are formed at G-C (particularly Py-G-C), G-T and, to a lesser extent, A-T sequences Furthermore, the frequency of various types of substitutions was consistent with selective incorporation of A and T residues opposite apyrimidinic sites at these sequences The highly selective nature of bleomycin-induced mutations may explain the lack of mutagenesis by this compound in a number of reversion assays

Protein Components of Bacteriophages λ and λ Virulent

Abstract: Parallel studies have been made of the protein coats of the temperate bacteriophage lambda and of a deletion mutant, lambda virulent. A new method for preparing ghosts of both phages by the action of Cu(++) is described. Protein ghosts of both phages can be dissolved in citrate at pH values below 3, more rapidly in the presence of 8 m urea. Both phages yielded three apparently identical protein components which can be separated by thin-layer gel filtration and thin-layer gel electrophoresis. The protein of molecular weight 47,000 +/- 1,500 represents about 55% of the protein of the ghosts and is therefore likely to be the subunit of the head. The other proteins of molecular weight 30,000 +/- 1,500 and 16,000 +/- 1,500 represent approximately 25% and 20% of the protein, respectively. Amino acid analyses of the ghosts from the two phages have been carried out and show no significant differences. The buoyant density of phage lambda virulent is 0.016 g/ml less than that of lambda. Since no differences have been found in the protein components of the two phages, this indicates that the virulent mutant contains approximately 16% less deoxyribonucleic acid than the temperate phage.