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At least 343 records · Page 19Linked to original sources
PubMed1995

DNA sequence of tail fiber genes of coliphage 186 and evidence for a common ancestor shared by dsDNA phage fiber genes.

We present here the nucleotide sequence of the tail fiber genes of phage 186. Marker rescue was used to associate an open reading frame (ORF) of 462 codons with the previously known tail gene K. A downstream ORF, encoding a 166-amino-acid product, was designated orf 45. Comparative studies suggested that K encodes the tail fiber protein and that orf 45 encodes an assembly protein. K protein contains a succession of short amino acid sequences (motifs) that are homologous with sequences from the tail fiber proteins of unrelated bacteriophages. The fact that these sequence motifs are variously present in the tail fiber proteins of unrelated bacteriophages has been advanced as evidence for horizontal transfer in the evolution of the associated tail fiber genes. However, the fact that the order of the various motifs in the proteins is invariant emphasizes the probability that independent divergence from a common ancestor also played a major role in the evolution of the tail fiber genes.

Amino Acid Sequence↗
PubMed1995

Tail sheath and tail tube genes of the temperate coliphage 186.

The nucleotide sequence of the phage 186 genome from 46.3-52.5% was determined and was found to contain two open reading frames highly similar to the tail sheath gene FI and tail tube gene FII of phage P2. The reading frames were identified as genes J and I by marker rescue experiments. A late promoter pJ was identified by galK reporter and primer extension studies. Northern analysis suggested that the pJ transcript predominantly terminated immediately after gene I, although some transcripts could extend to the terminator tB at 67.3%.

Amino Acid Sequence↗
PubMed1998

The late-expressed region of the temperate coliphage 186 genome.

The late-lytic region of the genome of bacteriophage 186 encodes the phage proteins that synthesize the complex viral particle and lyse the bacterial host. We report the completion of the DNA sequence of the late region and the assignment of 18 previously identified genes to open reading frames in the sequence. The 186 late region is similar to the late region of phage P2, sharing 26 genes of known function: the single gene for activation of late gene transcription, 6 genes for construction of DNA-containing heads, 16 for tail morphogenesis, and 3 for cell lysis. We identified two 186 late genes with unknown function; one is homologous to previously unrecognised genes in P2, HP1, and phiCTX, and the other may modulate DNA packaging. The 186 late region, like the rest of the genome, lacks the lysogenic conversion genes that are carried by P2, allowing the 186 late region to be transcribed from only three late promoters rather than four. The relative absence of lysogenic conversion genes in 186 suggests that the two phages have evolved to use the lytic and lysogenic reproductive modes to different extents.

Amino Acid Sequence↗
PubMed1975

The starting point and direction of rolling-circle replicative intermediates of coliphage lambda DNA.

Intermediates of lambda DNA replication in the second half of the latent period after phage lambda infection were isolated and investigated in the electron microscope by denaturation mapping. The isolated replicative forms (RF) are predominantly single branched circular DNA. The starting points of replication in these lariat molecules located at the same region as the first round lambda DNA replication. About 60% of the RF replicate from left to right and the other 40% replicate in the reverse direction. The free ends of the tails are located at many sites on the lambda genome. Replicating circles with a linear DNA tail longer than one unit length of lambda genome represent about 30% of the replicating molecules. These long linear tails (concatemers) produced by the rolling-circle (Gilbert and Dressler, 1968; Eisen et al., 1968; Skalka et al., 1972; Takahashi, 1974) are one of the best candidates for a precursor DNA of progeny phage.

Chromosome Mapping↗
PubMed1975

Host factor for coliphage Qbeta RNA replication is present in Pseudomonas putida.

Host Factor (HF)1, is a 12000 molecular weight polypeptide that is found in uninfected Escherichia coli and is required as a hexamer along with Qbeta replicase for in vitro replication of Qbeta phage RNA. It has recently been found to be associated with ribosomes and to bind tightly to poly(A). We report here the identification and purification of HF from Pseudomonas putida. HF can be detected in crude extracts by both functional activity in the Qbeta RNA replication assay and by immunodiffusion with antibody made against E. coli HF. HF from E. coli and P. putida chromatograph similarly on DEAE-cellulose and phosphocellulose. They have similar but not identical molecular weights as judged by SES-polyacrylamide gel electrophoresis. Like E. coli HF, P. putida HF was found to be associated with ribosomes and to bind tightly to poly(A). Furthermore, the pure protein from P. putida has full funcitonal activity in the in vitro Qbeta RNA replication assay. The findings that HF has been conserved during evolution, is associated with ribosomes, and binds poly(A), suggest that HF may be an important translational element in uninfected cells and that its role involves an interaction with RNA.

Coliphages↗