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: This phage has many advantages for studying the properties and mechanism of formation of duplication mutants, and the dependence of phage buoyant density on DNA length provides a nonspecific selection method for mutants which have longer DNA molecules.
Abstract: Gene duplication followed by independent evolution of the duplicated genes appears to be a basic feature of the genetics of higher organisms (see Bryson and Vogel, 1965). Such duplications are rare in Escherichia coli as judged by measurements of repeating DNA sequences (Britten and Kohne, 1968), although there are multiple copies of the ribosomal RNA genes in E. coli (Yankofsky and Spiegelman, 1962; Moore and McCarthy, 1967). There have been few studies of tandem duplications in phages. Duplications in the T4 r II region have been obtained by a strong selection technique (Weil et al., 1965; Parma and Ingraham, 1970). We have found that many of the spontaneous “revertants” of the deletion mutant t del 33 (Franklin, 1967) are duplication mutants, with changes at different locations on the phage chromosome. This phage has many advantages for studying the properties and mechanism of formation of duplication mutants. Some advantages which we have exploited in the present work are as follows. (1) Since the base sequence in 80- λ hy 1 DNA is nonpermuted and the phage chromosome can be extracted as a DNA molecule of definite length, a duplication mutant can be identified as such and the end points of the duplicated segment can be located by electron microscopy of DNA heteroduplexes. (2) The dependence of phage buoyant density on DNA length provides a nonspecific selection method for mutants which have longer DNA molecules. (Selection by plaque morphology is also possible in many cases.) (3) An independent method of identifying duplication mutants is based...
49 citations
TL;DR: Characterization of the cross-linked peptide disclosed that amino acids required for DNA-binding specificity resided within a 20-kDa peptide at the N-terminal end, providing a basis for further understanding of the structure and function of beta protein.
49 citations
TL;DR: It is shown that the E. coli p40mos binds ATP analog p-fluorosulfonylbenzoyladenosine and exhibits ATPase activity.
Abstract: The nucleotide sequence of the Moloney murine sarcoma virus strain HT-1 (HT1MSV) mos gene differs from that of the cellular mos gene in three positions, but these are silent changes, and the amino acid sequence of the v-mos and c-mos open reading frames are identical. We have overproduced the mos HT1MSV (equivalent to c-mos) in Escherichia coli under the control of phage lambda promoter (pL). The E. coli p40mos protein thus obtained was partially purified and examined for several biochemical activities. We show that the p40mos binds ATP analog p-fluorosulfonylbenzoyladenosine and exhibits ATPase activity.
49 citations
TL;DR: The prediction from sedimentation properties that one intracellular form of lambda DNA is a twisted, closed-circular molecule has been confirmed by observation in the electron microscope, and a new consequence of DNA circularity is evident from these studies.
49 citations
TL;DR: It is proposed that the disappearance of the S fraction reflects a rpoH‐dependent processing, the membrane destruction explains the lethality of the rPoH mutation at elevated temperatures, and the protection of the inner membrane integrity is an important physiological function of the heat‐shock response.
Abstract: Heat shock induces protein aggregation in Escherichia coli and E. coli (lambda cl857). The aggregates (S fraction) appear 15 min post-induction and are separable from membranes by sucrose density-gradient centrifugation. The S fraction quickly disappears in wild type strains but persists in rpoH mutant with concomitant quick inner membrane destruction. We propose that: (1) the disappearance of the S fraction reflects a rpoH-dependent processing, (2) the membrane destruction explains the lethality of the rpoH mutation at elevated temperatures; and (3) the protection of the inner membrane integrity is an important physiological function of the heat-shock response. We assume that the S fraction of aggregated proteins represents the signal inducing the heat-shock response. The prophage thermo-induction results in an increase (35 min post-induction) in the A fraction resembling that of the adhesion zones of the membranes. This fraction is greater than the corresponding fraction from uninduced cells. The increase is mediated by the lambda late genes, since it is absent in the induced E. coli (lambda cl857 Qam21). Since heat shock is widely used for induction of the lambda promoters in expression vectors it is possible that the formation of the protein aggregates (though transient in WT strains) and/or the fragility of membranes in rpoH mutants may be the cause of poor expression of cloned genes or may lead to mistaken localization of their expression products.
49 citations