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.

Neither absence nor excess of λ O initiator‐digesting ClpXP protease affects λ plasmid or phage replication in Escherichia coli

Abstract: Owing to rapid proteolysis of the coliphage lambda-coded initiator protein, lambda O, this protein is considered to carry a rate-limiting step in lambda DNA replication. The discovery of ClpXP protease responsible for lambda O protein turnover allowed an opportunity to verify this hypothesis. However, neither absence nor excess of this protease significantly affected the transformation efficiency and copy number of lambda plasmid, or the kinetics of the lambda phage growth. These results are also incompatible with the hypothesis that the stabilization of lambda O plays a role in the switch from early (circle-to-circle) to late (rolling-circle) lambda phage DNA replication. Transcriptional activation of ori lambda, probably assisted by the Escherichia coli DnaA function, remains as the possible rate-limiting step in lambda DNA replication.

Gene transfer to human cells: transducing phage lambda plac gene expression in GMI-gangliosidosis fibroblasts.

Abstract: Genetic information from the bacterium Escherichia coli was transferred to human cells by means of the specialized transducing phage lambda plac carrying the bacterial z gene for the enzyme beta-galactosidase (geta-D-galactoside galactohydrolase, EC 3.2.1.23). As recipient cells, cultured skin fibroblasts from a patient with generalized gangliosidosis (GMI-gangliosidosis Type I) characterized by a severe deficiency of beta-galactosidase activity were used. The deficient human cells were incubated with the bacteriophage lambda plac or lambda plac DNA and beta-galactosidase activity was measured in order to detect gene transfer and acceptance of the prokaryotic information in the mammalian system for transcription and translation. The expression of the phage genome in the deficient fibroblasts could be demonstrated by detection of higher beta-galactosidase activity after incubation with phage lambda plac in three out of 19 experiments and in four out of 16 experiments after treatment with lambda plac DNA. Lambda plac DNA induced much higher enzyme activities than infective phage particles. Immunochemical and physicochemical assays could not distinguish the induced beta-galactosidase activity from that of the z-gene product of E. coli.

System for efficient isolation of genes using probes

Abstract: Systems are provided for the dual purpose of cloning genes using antibodies as probes and isolating unknown proteins encoded by cloned DNA. The method employs a vector derived from phage which is used in combination with a high frequency lysogenic host. The vector is further characterized by having an inducible promoter regulating expression of a gene into which the foreign DNA may be introduced to produce a fused protein, and controlled induction of the prophage with rapid increase in copy number and high level transcription of foreign DNA. The technique is exemplified with a specific lambda phage construct in conjunction with the β-galactosidase structural gene lacZ.

Molecular analysis of the hsp (groE) operon of Leptospira interrogans serovar copenhageni.

Abstract: A chromosomal gene library of Leptospira interrogans serovar copenhageni strain Wijnberg was constructed in phage lambda gt11. Plaque immunoassay with R alpha P64 antiserum identified one clone expressing a putative groEL homologue. DNA sequence analysis of the 2.4 kb EcoRI-Bam HI cloned fragment from strain Wijnberg revealed two open reading frames encoding polypeptides of 10.5 kDa (Hsp10) and 58 kDa (Hsp58). Sequence comparison of the deduced amino acid sequences of these ORFs confirmed the operon as the groE equivalent of Leptospira. Transcriptional analysis suggested that this operon is primarily under the control of an E sigma 70 promoter element. However, both Hsp10 and Hsp58 were overexpressed under heat-shock conditions as determined by [35S]-methionine pulse labelling experiments. As no functional heat-shock promoter could be identified, a 9bp inverted repeat, located between the transcription and translation start sites, may play a role in the upregulation of this operon under heat-shock conditions, similar to mechanisms described for several Gram-positive organisms.