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Biomedical subjects

H Hashimoto

Publications and source records attributed to H Hashimoto.

At least 1,441 records · Page 80Linked to original sources
PubMed1974

Round of replication mutant of a drug resistance factor.

A derivative of the R factor NR1 (called R12) has been isolated which undergoes an increased number of rounds of replication each division cycle in Proteus mirabilis, Escherichia coli, and Salmonella typhimurium. The alteration resulting in the increased number of copies (round of replication mutation) is associated with the transfer factor component of the R factor. R12 has the same drug resistance pattern as NR1, is the same size as shown by sedimentation in a sucrose gradient and electron microscopy (63 x 10(6) daltons), and has the same partial denaturation map. The level of the R factor gene product chloramphenicol acetyltransferase has been examined in P. mirabilis and was found to be consistent with gene dosage effects. The plasmid to chromosomal deoxyribonucleic acid ratio of NR1 increases several fold after entry into stationary phase, whereas this ratio for R12 remains approximately constant. Individual copies of R12 are selected at random for replication from a multicopy plasmid pool. A smaller percentage of R12 copies replicate during amino acid starvation than has previously been found for NR1 in similar experiments.

Acyltransferases↗
PubMed1974

R-factor mutant capable of specifying hypersynthesis of penicillinase.

The physical characteristics of a mutant, R(M201-2), capable of conferring high and stable ampicillion resistance was analyzed. The R(M201-2) and its parent R-factor deoxyribonucleic acid (DNA) could be isolated as an extrachromosomal and covalently closed circular form. Their buoyant densities were both 1.712 g/cm(3), and their molecular weights were about 82 x 10(6) and 64 x 10(6), respectively, when measured by CsCl and sucrose density gradient analyses. The contour lengths by electron microscopy were 35.9 +/- 0.6 and 31.0 +/- 0.6 mum, respectively. By using the extracted R-factor DNA, the mutant and parent characters were transformable to another Escherichia coli strain. The mutant R factor showed an increased amount of DNA even after conjugal transfer to Proteus. An increase in the size of R-factor DNA was thus considered to be the cause of the high level of ampicillin resistance.

Ampicillin↗
PubMed1973

Mutation of R factors capable of specifying hypersynthesis of penicillinase.

When strains harboring R factor and showing ampicillin (APC) resistance were inoculated on plates containing various concentrations of APC, mutants carrying various levels of APC resistance occurred at high frequencies. Increases in the level of APC resistance were due to a quantitative increase in the formation of penicillinase. By conjugation experiments and transduction analysis, the mutation was found to affect the gene (amp) governing APC resistance on the R factor. The R-factor mutants carrying high and stable APC resistance were conjugally transferred at the same frequency as their parent R factors, and the level of their resistance to drugs other than APC was not distinct from that conferred by their parents. Such R-factor mutants could easily be obtained from wild-type R factors carrying low APC resistance. The hypersynthesis of penicillinase by such R-factor mutants was considered to be due to the replication of the amp gene on the R factor at hyper-rates and the integration of multiple copies of the amp gene (amp-hyper) in the R-factor genome.

Ampicillin↗
PubMed1973

Some properties of acid protease from the thermophilic fungus, Penicillium duponti K1014.

A purified acid protease from a true thermophilic fungus, Penicillium duponti K1014, was most active at pH 2.5 for milk casein and at pH 3.0 for hemoglobin. The enzyme was stable at a pH range of 2.5 to 6.0 at 30 C for 20 h. The acid protease retained full activity after 1 h at 60 C at a pH range between 3.5 and 5.5. At the most stable pH of 4.5, more than 65% of its activity remained after heat treatment for 1 h at 70 C. These thermal properties show the enzyme as a thermophilic protein. The enzyme activity was strongly inhibited by sodium lauryl sulfate and oxidizing reagents such as potassium permanganate and N-bromosuccinimide. No inhibition was caused by chelating reagents, potato inhibitor, and those reagents which convert sulfhydryl groups to mercaptides. Reducing reagents showed an activating effect. The enzyme showed the trypsinogen-activating property at an acidic pH range; optimal trypsinogen activation was obtained at a pH of approximately 3.0. The isoelectric point of the enzyme was estimated to be pH 3.89 by disk electrofocusing. By using gel filtration, an approximate value of 41,000 was estimated for the molecular weight.

Caseins↗
PubMed1973

Production and purification of acid protease from the thermophilic fungus, Penicillium duponti K1014.

A thermophilic fungus, Penicillium duponti K1014, produced an acid protease in a submerged culture. Maximum enzyme production, in a 30-liter fermentor at a preselected optimum growth temperature of 50 C, occurred after 3 days. The productivity of the enzyme was associated with changes of viscosity and pH of culture broth during the growth. The acid protease was isolated from the culture filtrates and was purified ninefold by alcohol precipitation, column chromatography on O-(diethylaminoethyl)cellulose, batchwise treatment with O-(carboxymethyl)cellulose, and by gel filtration. The purified enzyme was homogeneous on disk electrophoresis and sedimentation analysis. The sedimentation constant s(20.w), calculated at a concentration of 0.64%, was 3.98S.

Chemical Precipitation↗