Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “BACTERIOPHAGE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMed1988

DNA twisting and the affinity of bacteriophage 434 operator for bacteriophage 434 repressor.

The affinity of the Escherichia coli phage 434 operator for phage 434 repressor is affected by changes in the sequence of the noncontacted base pairs near the operator's center. The results presented here show that base composition near the center of the operator affects the operator's affinity for repressor by altering the ease with which the operator can be overtwisted into the proper configuration for complex formation. We show that both DNA flexibility and repressor flexibility influence the strength of the repressor-operator interaction: an operator with a single-strand nick at its center has a higher affinity for repressor than does the intact operator: and a repressor bearing a mutation that results in a relaxed dimer interaction is less sensitive than is wild type to changes in the flexibility of the operator. We show that the effect of noncontacted base pairs on operator affinity is independent of the slight overall bend of the operator seen in the repressor-operator complex. Central sequence effects on affinity for repressor are independent of the identity of adjacent base pairs, suggesting that the structure of the individual base pairs, not interactions between them, are responsible for the different torsional rigidities of different operators.

Base Composition↗
PubMed1991

Bending of synthetic bacteriophage 434 operators by bacteriophage 434 proteins.

The extent of DNA bending induced by 434 repressor, its amino terminal DNA binding domain (R1-69), and 434 Cro was studied by gel shift assay. The results show that 434 repressor and R1-69 bend DNA to the same extent. 434 Cro-induced DNA bends are similar to those seen with the 434 repressor proteins. On approximately 265 base pair fragments, the cyclic AMP receptor protein of Escherichia coli (CRP) produces larger mobility shifts than does 434 repressor. This indicates that the 434 proteins bend DNA to a much smaller extent than does CRP. The effects of central operator sequence on intrinsic and 434 protein-induced DNA bending was also examined by gel shift assay. Two 434 operators having different central sequences and affinities for 434 proteins display no static bending. The amount of gel shift induced by 434 repressor on these operators is identical, showing that the 434 repressor bends operators with different central sequences to the same extent. Hence, mutations in the central region of the operator do not influence the bent structure of the unbound or bound operator.

Base Sequence↗
PubMed1993

Bacteriophage Nf DNA region controlling late transcription: structural and functional homology with bacteriophage phi 29.

The putative region for the control of late transcription of the Bacillus subtilis phage Nf has been identified by DNA sequence homology with the equivalent region of the evolutionary related phage phi 29. A similar arrangement of early and late promoters has been detected in the two phages, suggesting that viral transcription could be regulated in a similar way at late times of the infection. Transcription of late genes requires the presence of a viral early protein, gpF in phage Nf and p4 in phage phi 29, being the latter known to bind to a DNA region located upstream from the phage phi 29 late promoter. We have identified a DNA region located upstream from the putative late promoter of phage Nf that is probably involved in binding protein gpF. Furthermore, we show that the phage phi 29 protein p4 is able to bind to this region and activate transcription from the phage Nf putative late promoter. Sequence alignment has also revealed the existence of significant internal homology between the two early promoters contained in this region of each phage.

Bacillus Phages↗
PubMed1976

Studies on bacteriophage distribution: virulent and temperate bacteriophage content of mammalian feces.

Freshly voided samples of the feces of cows, pigs, and humans were analyzed for the enumeration of cell-free plaque-forming units (PFU) of coliphages and Salmonella phages. Coliphage PFU counts per gram (wet weight) of feces were found to range from less than 10(1) to greater than 10(7). Salmonella phages were found in three out of five porcine samples, but none were found in the four bovine samples analyzed. Virulent coliphages related to the phiX174/S13 serological group showed some "habitat preference" in that the S13 type of phages was found only in pig feces, whereas the phiX174 type of phages was found only in cow dung. Temperate coliphages were detectable in a majority of samples of both human and porcine origin but were infrequently found in bovine samples. About 80% of the temperate coliphages of fecal origin have been found to be serologically related to phage HK022 (Dhillon and Dhillon, 1973), and all are efficiently inducible by ultraviolet light irradiation. However, considerable diversity with the group was found when the prophage immunity pattern of 10 randomly selected isolates was examined.

Animals↗
PubMed1978

Adjacent insertion sequences IS2 and IS5 in bacteriophage Mu mutants and an IS5 in a lambda darg bacteriophage.

Using electron microscopic heteroduplex analysis, we have demonstrated that an insertion found in a Mu prophage and in some infectious. Mu deletion-substitution mutants derived from it consists of bacterial insertion sequence IS2 linked directly to IS5. Other infectious Mu mutants derived from the same lysogen have only IS5 or a portion of IS2. In addition, we have found that an independent insertion in a transducing phage, lambda 13 dargB2, is IS5. The ends of IS5 are short, inverted duplications of each other. These observations support the notion that the DNA insertion previously designated IS5 on the basis of a single example in lambda KH100 is a bona fide bacterial insertion sequence.

Coliphages↗