Phage Mu

Harshey, Rasika M.

doi:10.1007/978-1-4684-5424-6_6

Cited by 30 publications

(11 citation statements)

References 212 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our results lead us to propose an essential function for the bacterial DNA covalently attached to both ends of Mu virion DNA (35). These sequences (50-150 bp at the left end and 500-3000 bp at the right end) are acquired as a result of headful packaging of Mu DNA integrated into the bacterial genome.…”

Section: Discussionmentioning

confidence: 81%

Crucial role for DNA supercoiling in Mu transposition: a kinetic study.

Wang

Harshey

1994

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

DNA supercoiling plays an indispensable role in an early step of bacteriophage Mu transposition. This step involves formation of a nudeoprotein complex in which the Mu ends synapse and undergo two concerted single-strand cleavages. We describe a kinetic analysis of the role of supercoiling in the Mu-end synapsis reaction as measured by the cleavage assay. We observe a dependence of the reaction rate on superhelical density as well as on the length of Mu donor plasmid DNA. The reaction has a high activation enthalpy (-67 kcal/mol). These results imply that the free energy of supercoiling is used direcly to lower the activation barrier of the rate-limiting step of the reaction. Only the free energy of supercoiling associated with DNA outside the Mu ends appears to be utilized, implying that the Mu ends come together before the supercoiling energy is used. Our results suggest an essential function for the bacterial sequences attached to the ends of Mu virion DNA. Fig. 1). The Mu A protein exists in solution as a monomer (6) and binds to several specific sites at the left (attL) and right (attR) ends of Mu (9-11). This protein also binds to internal enhancer sites (12)(13)(14). In the presence of Mg2+, a stable synaptic complex can be isolated in which the Mu ends have undergone cleavage (2, 3) and the Mu A protein has tetramerized (7). In the presence of Ca2e, a precleavage synaptic complex accumulates ( Fig. 1; ref. 4).DNA supercoiling influences nearly all DNA-protein transactions by its effect on the energetics, hydrodynamic behavior, and physical structure of DNA (15-18). Supercoiling is required in the transposition step that leads to Mu-end cleavage (2). However, the superhelical density required can be reduced by the E. coli IHF (integration host factor) protein, which binds in the enhancer region (ref. i.e., the activation energy-dictates the overall reaction rate (21):where k is the rate constant, Z is a frequency factor, and AG* is the free energy of activation.Acceleration of reactions can be achieved either by reducing the energy level of the transition state, as most enzymes do, or by lifting the energy level of the substrates. In the Mu-end cleavage reaction, we propose to test whether the supercoiling energy of DNA directly contributes to reducing the free energy of activation of the rate-limiting step. Assuming that there is a single rate-limiting step in the cleavage reaction and that the supercoiling energy is used directly to lower the activation barrier, we have AG* -AG*O -iiAGS, [2] where AGt°is the activation free energy in the absence of supercoils and AGs is the free energy of supercoiling. 21 is a factor we have introduced to represent the fraction of the utilizable supercoil energy.Abbreviations: IHF, integration host factor; EtdBr, ethidium bromide. 699F

show abstract

Section: Discussionmentioning

confidence: 81%

Crucial role for DNA supercoiling in Mu transposition: a kinetic study.

Wang

Harshey

1994

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…Several bacteriophages are capable of altering their host range via a sitespecific recombination system that inverts the sequence that determines the host range (30). For example, bacteriophage Mu is a broad-host-range phage capable of forming plaques on several bacterial species (11). The Mu genome contains tail fiber gene S, which encodes a site recognized by a Mu-encoded invertase, with a second site beyond the gene in inverted orientation.…”

Section: Discussionmentioning

confidence: 99%

Morphological, Host Range, and Genetic Characterization of Two Coliphages

Goodridge

Gallaccio

Griffiths

2003

Appl Environ Microbiol

View full text Add to dashboard Cite

Two coliphages, AR1 and LG1, were characterized based on their morphological, host range, and genetic properties. Transmission electron microscopy showed that both phages belonged to the Myoviridae; phage particles of LG1 were smaller than those of AR1 and had an isometric head 68 nm in diameter and a complex contractile tail 111 nm in length. Transmission electron micrographs of AR1 showed phage particles consisting of an elongated isometric head of 103 by 74 nm and a complex contractile tail 116 nm in length. Both phages were extensively tested on many strains of Escherichia coli and other enterobacteria. The results showed that both phages could infect many serotypes of E. coli. Among the enterobacteria, Proteus mirabilis, Shigella dysenteriae, and two Salmonella strains were lysed by the phages. The genetic material of AR1 and LG1 was characterized. Phage LG1 had a genome size of 49.5 kb compared to 150 kb for AR1. Restriction endonuclease analysis showed that several restriction enzymes could degrade DNA from both phages. The morphological, genome size, and restriction endonuclease similarities between AR1 and phage T4 were striking. Southern hybridizations showed that AR1 and T4 are genetically related. The wide host ranges of phages AR1 and LG1 suggest that they may be useful as biocontrol, therapeutic, or diagnostic agents to control and detect the prevalence of E. coli in animals and food.

show abstract

“…Neisseria meningitidis cognate prophages Pnm2 in strain Z2491 and NeisMu1 in strain MC58 (Parkhill et al ., 2000; Tettelin et al ., 2000) are mosaic relatives of the Mu‐like group of phages [ E. coli phage Mu and three largely intact prophages, FluMu, Sp18 and Pnm1, present in H. influenzae Rd, E. coli Sakai and N. meningitidis Z2491, respectively, have been completely sequenced (Fleischmann et al ., 1995; Parkhill et al ., 2000; Hayashi et al ., 2001a; Morgan et al ., 2002); ‘NeisMu1’ is a provisional name used here as the original annotators did not name this element]. This type of phage integrates essentially randomly by a transposition mechanism (reviewed by Harshey, 1988). Thus, as the number of potential integration targets in any genome is huge, natural prophages of this type that are found at identical positions in the genomes of two independently isolated bacteria are extremely likely to be descendants of the same past phage integration event.…”

Section: Prophage Evolution and Genetic Exchange Between Prophagesmentioning

confidence: 99%

Prophages and bacterial genomics: what have we learned so far?

Casjens

2003

Molecular Microbiology

780

815

View full text Add to dashboard Cite

EpigraphThere is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact. Mark Twain 1883 Life on the Mississippi SummaryBacterial genome nucleotide sequences are being completed at a rapid and increasing rate. Integrated virus genomes (prophages) are common in such genomes. Fifty-one of the 82 such genomes published to date carry prophages, and these contain 230 recognizable putative prophages. Prophages can constitute as much as 10-20% of a bacterium's genome and are major contributors to differences between individuals within species. Many of these prophages appear to be defective and are in a state of mutational decay. Prophages, including defective ones, can contribute important biological properties to their bacterial hosts. Therefore, if we are to comprehend bacterial genomes fully, it is essential that we are able to recognize accurately and understand their prophages from nucleotide sequence analysis. Analysis of the evolution of prophages can shed light on the evolution of both bacteriophages and their hosts. Comparison of the Rac prophages in the sequenced genomes of three Escherichia coli strains and the Pnm prophages in two Neisseria meningitidis strains suggests that some prophages can lie in residence for very long times, perhaps millions of years, and that recombination events have occurred between related prophages that reside at different locations in a bacterium's genome. In addition, many genes in defective prophages remain functional, so a significant portion of the temperate bacteriophage gene pool resides in prophages.Prophage biology

show abstract

Phage Mu

Cited by 30 publications

References 212 publications

Crucial role for DNA supercoiling in Mu transposition: a kinetic study.

Crucial role for DNA supercoiling in Mu transposition: a kinetic study.

Morphological, Host Range, and Genetic Characterization of Two Coliphages

Prophages and bacterial genomics: what have we learned so far?

Contact Info

Product

Resources

About