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Biomedical subjects

K Isono

Publications and source records attributed to K Isono.

At least 523 records · Page 29Linked to original sources
PubMed1976

Isolation and characterization of temperature-sensitive mutants of Escherichia coli with altered ribosomal proteins.

The ribosomal proteins of temperature-sensitive mutants of Escherichia coli isolated independently after mutagenesis with nitrosoguanidine were analyzed by two-dimensional gel electrophoresis. Out of 400 mutants analyzed, 60 mutants (15%) showed alterations in a total of 22 different ribosomal proteins. The proteins altered in these mutants are S2, S4, S6, S7, S8, S10, S15, S16, S18, L1, L3, L6, L10, L11, L14, L15, L17, L18, L19, L22, L23 and L24. A large number of them (25 mutants) have mutations in protein S4 of the small subunit, while four mutants showed alterations in protein L6 of the large subunit. The importance of these mutants for structural and functional analyses of ribosomes is discussed.

Electrophoresis, Polyacrylamide Gel↗
PubMed1976

Lack of ribosomal protein S1 in Bacillus stearothermophilus.

The 30S ribosomal subunit of Bacillus stearothermophilus migrated as a single band when electrophoresed on agarose-acrylamide composite gels. The addition of the ribosomal protein S1 purified from Escherichia coli resulted in the appearance of an additional band migrating more slowly; 14C-labeled S1 of E. coli was shown to be associated only with this form. Antibody against E. coli protein S1 did not crossreact with either the total 30S ribosomal proteins or the postribosomal supernatant from B. stearothermophilus. These results indicate that B. stearothermophilus lacks a protein equivalent to E. coli S1 and may explain our previous finding [Eur. J. Biochem. 56, 15-22 (1975) that E. coli S1 greatly stimulated the translation by B. stearothermophilus ribosomes of f2 phage RNA.

Bacterial Proteins↗
PubMed1975

Biosynthesis of the polyoxins, nucleoside peptide antibiotics: glutamate as an origin of 2-amino-2-deoxy-L-xylonic acid (polyoxamic acid).

The biosynthetic origin of the carbon skeleton of 2-amino-2-deoxy-L-xylonic acid (polyoxamic acid) is described. This aminoaldonic acid is the N terminus of the nucleoside peptide antibiotics, the polyoxins, produced by Streptomyces cacaoi var. asoensis. In vivo experiments concerning incorporation and distribution of radioactivity from a number of 14C-labeled compounds have clearly shown that the carbon skeleton of glutamate is a precursor for this aminoaldonic acid and sugars are incorporated only after their conversion into gluamate through the glycolytic and the tricarboxylic acid cycle pathways. Experiments utilizing [14C]-acetate and succinate have also indicated multiple passages through the Krebs cycle are operating before their incorporation into polyoxamic acid via glutamate. The distribution of 14C between C-1 and C-5 of polyoxamic acid from [5-14C]glutamate experiment has indicated that 40% of glutamate incorporated only after the reversible conversion into alpha-ketoglutarate followed by the passage through the Krebs cycle. Lack of incorporation of 3H in the [1-14C;2-3H]- and [5-14C;2-3H]glutamate experiments is discussed in terms of a reaction(s) between glutamate and polyoxamic acid.

Acetates↗
PubMed1975

Role of ribosomal protein S1 in portein synthesis: effects of its addition to Bacillus stearothermophilus cell-free system.

Products of the f2 phage RNA-directed protein synthesizing systems in vitro, derived from Escherichia coli and Bacillus stearothermophilus, were analyzed. In contrast to other reports, it was found that B. stearothermophilus ribosomes synthesized phage coat protein when the high-speed (100 000 X g) supernatant (S100) and ribosomal wash (crude initiation factors) of homologous origin were used. Furthermore, a marked stimulation of coat protein synthesis was observed with B. stearothermophilus ribosomes when either S100 or ribosomal wash or both from E. coli cells were used instead of the respective homologous components. The principle responsible for this stimulation was identified as the 30-S ribosomal protein S1 present in S100 and ribosomal wash. Purified S1 from E. coli at roughly one-to-one molar ratio to ribosomes resulted in about 10-fold stimulation of the incorporation of [14C]valine when added to the B. stearothermophilus system. This stimulation was observed mainly in the synthesis of coat protein and replicase.

Amino Acids↗
PubMed1975

Purification and characterization of 30-S ribosomal proteins from Bacillus stearothermophilus.

Twenty-three proteins were identified by two-dimensional eletrophoresis on polyacrylamide-gel slabs in the 30-S ribosomal subunit of Bacillus stearothermophilus strain 799. They were designated as B-S1 through B-S21, B-Sa and B-Sb and purified on carboxymethyl-cellulose and Sephadex G100 in the presence of 6 M urea. Their molecular weight was estimated by dodecyl-sulfate-gel electrophoresis and their amino acid composition was determined after acid hydrolysis. Results obtained for the individual proteins were essentially similar to those for Escherichia coli 30-S proteins with some characteristic differences.

Amino Acids↗
PubMed1975

Histological characteristics and postoperative course of gastric carcinoma.

The histological features of gastric carcinoma in patients survived more than 5 years after the resection were reviewed. In general prognosis and length of survival were related clearly to the degree of malignancy of cancer. Duration of the remission was also reciprocaly related. Certain type of carcinoma simplex or undifferentiated carcinoma was associated with unexpectedly more favorable prognosis. Paradoxical relation was also demonstrated between degree of atypism in adenocarcinoma papillare with introversive pseudopapillary pattern and its prognosis.

Adenocarcinoma, Papillary↗
PubMed1975

Biosynthesis of the polyoxins, nucleoside peptide antibiotics: a new metabolic role for L-isoleucine as a precursor for 3-ethylidene-L-azetidine-2-carboxylic acid (polyoximic acid).

The biosynthetic origin of the carbon skeleton of 3-ethylidene-L-azetidine-2-carboxylic acid (polyoximic acid) is described. This unique cyclic amino acid is the C terminus of the nucleoside peptide antibiotics, the polyoxins, elaborated by Streptomyces cacaoi var, asoensis. In vivo experiments show that 14-C from [1-14-C]isoleucine, [U-14-C]isoleucine, [1-14-C]methionine, [U-14-C]methionine, [U-14-C]threonine, and [1-14-C]glutamate is incorporated into polyoximic acid; however, 14-C from [5-14-C]glutamate and [methyl-14-C]methionine is not incorporated. The distribution of 14-C in polyoximic acid clearly shows that the intact carbon skeleton of L-isoleucine is utilized directly. The incorporation of 14-C from [U-14-C]methionine, [U-14-C]threonine, and [1-14-CA1glutamate into polyoximic acid occurred only after their conversion to isoleucine via 2-ketobutyrate. A scheme is presented in which either of the two beta-unsaturated amino acids isolated from Bankera fuligineoalba, L-2-amino-3-hydroxymethyl-3-pentenoic acid or L-2-amino-3-formyl-3-penetenoic acid, is regarded as a possible intermediate amino acid between isoleucine and polyoximic acid.

Antifungal Agents↗
PubMed1974

Chemical carcinogens as frameshift mutagens: Salmonella DNA sequence sensitive to mutagenesis by polycyclic carcinogens.

Other investigators have shown that several polycyclic carcinogens are frameshift mutagens in Salmonella. Mutagenic potency of these compounds is assessed by ability to induce reversion of histidine-requiring frameshift mutants to prototrophy. One frameshift mutation in the histidinol dehydrogenase gene, hisD3052, is unusually sensitive to mutagenesis by certain polycyclic carcinogens. We find that the 3052 mutation is a - 1 deletion, probably loss of a G.C pair from a DNA repeat of [unk]. The polycyclic carcinogens tested (e.g., 2-nitroso-fluorene) revert 3052 by deleting a [unk] doublet from the DNA sequence [unk], which is close to the 3052 site. This rare mispairing-prone sequence represents the carcinogen-sensitive "hotspot" in 3052. The ICR compounds, noncarcinogenic intercalating agents, show a broader specificity of mutagenesis. Reversion with these mutagens occurs predominantly by two mechanisms: one identical to that of the polycyclic carcinogens, and the other by +1 additions in a third DNA tract narrowly separated from the 3052 site. The alkylating carcinogen N-methyl-N'-nitro-N-nitrosoguanidine appears to have a similar dual specificity. DNA base changes in 3052 revertants have been correlated with properties of histidinol dehydrogenase in crude extracts. This correlation of DNA base sequence with electrophoretic and other properties of the mutant proteins allows one to analyze easily the specificity of new mutagens that mutate this strain.

Acridines↗