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Biomedical subjects

K Matsubara

Publications and source records attributed to K Matsubara.

At least 559 records · Page 31Linked to original sources
PubMed1977

Purification and properties of a lambda operator-binding protein which is expected to be autorepressor (tof protein) from E. coli carrying lambdadv plasmid.

In order to study the mode of action of the tof gene product, which is an "autorepressor" of the bacteriophage lambda and plasmid lambdadv, we have purified a DNA-binding protein which is specifically produced in bacteria carrying lambdadv. This protein possesses characteristics expected for the product of the tof gene, since it is produced under conditions where cI-repressor is not made, and since it binds to oL and oR operators on the lambda phage genome. The molecular weight of the native protein is 16,000-17,000 daltons, and the monomeric molecular weight as measured by gel electrophoresis in the presence of sodium dodecyl sulfate is about 10,000 daltons. Denaturation and renaturation experiments demonstrated that the native protein is a dimer of 10,000-dalton monomers. The lambdaDNA-specific binding protein is not produced in cells carrying i21dv or ø80dv.

Bacterial Proteins↗
PubMed1975

Role of the tof gene in the production and perpetuation of the lambdadv plasmid.

A series of lambda derivatives carrying tof mutations were tested for their ability to give rise to plasmid lambda dv. Phages carrying tof mutations that distorted expression of the pRoR-tof-OP operon, were unable to produce lambda dv. Phages carrying an altered tof gene, having only a moderate effect on the same operon, produced unstable lambdadv's. On the other hand, those tof mutants were only the expression of the pLoL-N-exo operon, but not that of the pRoR-tof-OP operon was affected, produced stable lambdadv's.

Coliphages↗
PubMed1975

Isolation and properties of a conditionally lethal bacteriophage lambda mutated in the chi region.

A thermosensitive lambda phage mutant was isolated which can grow at high temperature only in the presence of the lambda chi gene product supplied in trans. This mutation tn was mapped within the chi region, and lambda tn phage expressed the pRoR-OP operon only poorly at high temperature. Effects of the tn mutation on expression of other operons were also examined and compared with those observed with cro27 or some tof mutations.

Chromosome Mapping↗
PubMed1975

Mode of replication of plasmid lambda-dv-1.

About 20 copies of plasmid lambda-dv are perpetuated per host chromosome in Escherichia coli K12 cells. The mode of DNA replication of this plasmid lambda-dv was studied, using the density-labelling technique followed by banding in DsCl. It was shown that all the copies of plasmid lambda-dv are potentially capable of replicating roughly once a cell generation. Their replication occurs by random, that is a copy of the plasmid is taken out at random for replication from a pool, to which the two replicas resulting from replication are returned. Chloramphenicol did not inhibit the initiation of a new round of replication of the plasmid molecules, indicating that selection from the replication pool does not require concomitant protein synthesis.

Cell Division↗
PubMed1975

Characterization of defective simian virus 40 DNA: comparison between large-plaque and small-plaque types.

We characterized defective DNA molecules of large-plaque and small-plaque SV40 produced and accumulated during serial undiluted passages. The electron microscope heteroduplex method revealed that defective SV40 DNA contains deletions, insertions and substitutions. The majority of the large-plaque defective molecules had a simple deletion. The deletions were heterogeneous in size, and the sites of deletion appeared to be mostly overlapping. The majority of the small-plaque defective molecules had a deletion, and more than half of the deletion molecules also had an insertion at a separate site. The small-plaque SV40 genome appeared to have more sites for deletion to occur than large-plaque SV40, and the deletions have occurred at more than two sites. The change of a local nucleo tide sequence resulting from mutation may be related to the difference between the two plaque types.

Cell Transformation, Neoplastic↗
PubMed1975

Mutants of Escherichia coli which block head formation of lambda.

Five mutants of Escherichia coli K12 (lam 24, lam 25, lam 26, lam 27 and lam 646) that block head formation of lambda are described. In vitro complementation tests and electron microscopy demonstrated that in these bacteria phage tails were produced normally, whereas head formation was abnormal, aberrant head-related structures being produced. In lysates prepared from lam 24, lam 25 and lam 26, monsters and empty heads without tail were the predominant structures, whereas in lysates from lam 27 and lam 646, petit lambda and empty heads were the most common structures. The five lam mutations were located in two regions on the bacterial chromosome; lam 24, lam 25 and lam 26 were near the dnaB gene and lam 27 and lam 27 and lam 646 near the lac gene. It was suggested that the former three mutants are new isolates that belong to GroE mutants, whereas the latter two comprise a new group of mutants. Analyses of phage mutants (ov mutants) that overcome the interference by the lam 646 mutation revealed that this mutation blocks normal expression of the gene E of lambda.

Chromosome Mapping↗