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S Hiraga

Publications and source records attributed to S Hiraga.

234 records · Page 13Linked to original sources
PubMed1969

Temperature-sensitive repression of the tryptophan operon in Escherichia coli.

Mutants of Escherichia coli exhibiting temperature-sensitive repression of the tryptophan operon have been isolated among the revertants of a tryptophan auxotroph, trpS5, that produces an altered tryptophanyl transfer ribonucleic acid (tRNA) synthetase. Unlike the parental strain, these mutants grew in the absence of tryptophan at high but not at low temperature. When grown at 43.5 C with excess tryptophan (repression conditions), they produced 10 times more anthranilate synthetase than when grown at 36 C or lower temperatures. Similar, though less striking, temperature-sensitivity was observed with respect to the formation of tryptophan synthetase. Transduction mapping by phage P1 revealed that these mutants carry a mutation cotransducible with thr at 60 to 80%, in addition to trpS5, and that the former mutation is primarily responsible for the temperature-sensitive repression. These results suggest that the present mutants represent a novel type of mutation of the classical regulatory gene trpR, which probably determines the structure of a protein involved in repression of the tryptophan operon. In agreement with this conclusion, tRNA of several trpR mutants was found to be normal with respect to its tryptophan acceptability. It was also shown that the trpS5 allele, whether present in trpR or trpR(+) strains, produced appreciably higher amounts of anthranilate synthetase than the corresponding trpS(+) strains under repression conditions. This was particularly true at higher temperatures. These results provide further evidence for our previous conclusion that tryptophanyl-tRNA synthetase is somehow involved in repression of this operon.

Chromosome Mapping↗
PubMed1966

Regulation of synthesis of alkaline phosphatase by deoxyribonucleic acid synthesis in a constitutive mutant of Bacillus subtilis.

Hiraga, Sota (Osaka University, Osaka, Japan). Regulation of synthesis of alkaline phosphatase by deoxyribonucleic acid synthesis in a constitutive mutant of Bacillus subtilis. J. Bacteriol. 91:2192-2199. 1966.-It was found that synthesis of alkaline phosphatase (APase) correlated with deoxyribonucleic acid (DNA) synthesis in a partially constitutive mutant of Bacillus subtilis. When cultures of the mutant were made to undergo synchronous growth by germination of spores in an excess-phosphate medium, synthesis of APase was repressed at the beginning of DNA synthesis. If the initiation of DNA synthesis was inhibited by thymine starvation, the repression of APase was not observed. When DNA synthesis, previously initiated, was inhibited by thymine or uracil starvation, or by addition of mitomycin C, the repression was partially released at a later stage. In contrast, this correlation between repression and DNA synthesis was not observed in a repressible strain.

Alkaline Phosphatase↗
PubMedDate not supplied

Mutants defective in chromosome partitioning in E. coli.

Recent experimental results suggest that replicated daughter chromosomes (nucleoids) in Escherichia coli move non-progressively and abruptly at an early stage of the D (division) period from midcell toward the cell quarter positions, which will become the centres of the daughter cells. The chromosome positioning at the quarter positions was found to be controlled by the muk gene products. In muk mutants, normal size anucleate cells are spontaneously produced during cell division. The mukA gene is identical to the tolC gene encoding an outer membrane protein. The mukB gene codes for a 177-kDa protein. The amino acid sequence of the MukB protein deduced for the nucleotide sequence suggests that the MukB protein has five characteristic secondary structure domains: an amino-terminal globular domain containing a consensus sequence binding with ATP or another nucleotide. The central region of the protein consists of two alpha-helical coiled-coil domains and one globular domain. A carboxyl-terminal globular domain is rich in cysteine and positively charged residues arginine and lysine. Two MukB protein molecules might form a homodimer in the coiled-coil regions. The predicted secondary structure of the MukB protein suggests that the protein provides the force required for the positioning of nucleoids from midcell toward the cell quarters. The mukC and mukD genes are located at 88 and 41 min of the chromosome map, respectively.

Amino Acid Sequence↗
PubMedDate not supplied

Structure and function of the ftsH gene in Escherichia coli.

The ftsH mutant Y16 shows thermosensitive filamentation with reduced amounts of penicillin-binding protein 3 (PBP3) (Ferreira et al., 1987). Genetic analysis, however, showed that the lethality of the ftsH mutation was not due to a lack of PBP3 activity alone. The ftsH gene was cloned and sequenced and the FtsH protein was deduced to be a membrane protein of 70.7 kDa which has an ATP-binding domain. Highly significant homology of amino acid sequence was observed between FtsH protein and two eukaryotic proteins, yeast Saccharomyces cerevisiae Sec 18p and its mammalian homologue NSF, which are involved in protein transport pathways. This suggests that FtsH protein may act for translocation of specific proteins including PBP3 and at least one other additional protein essential for cell growth. Suppressor mutants of Y16, which were able to grow at 42 degrees C, were isolated, and the suppressor mutations (sfh) were mapped to 16 min. A wild type chromosomal fragment able to complement the sfh mutations was cloned. We also identified another gene (ftsJ) affecting cell division in the region upstream of the ftsH gene.

Bacterial Proteins↗
PubMedDate not supplied

Leptomeningeal dissemination of malignant glioma: immunohistochemical analysis of tenascin and glial fibrillary acidic protein.

Immunohistochemical expression of tenascin (TN) and glial fibrillary acidic protein (GFAP) was investigated in 9 human malignant gliomas with leptomeningeal dissemination. In these patients intracerebral glioma tissues obtained at operation and/or autopsy displayed localized expression of TN in tumor vessels and stroma. In contrast, TN was expressed in the tumor vessels, tumor stroma, and the cytoplasm of tumor cells to a high degree throughout all the leptomeningeal tumor tissues obtained at autopsy, whereas there was much less expression of GFAP in these tissues than at the primary site. These findings suggest that TN expression and decrease of GFAP expression in glioma tissue may be involved in the development of leptomeningeal dissemination.

Adolescent↗