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K Ikehara

Publications and source records attributed to K Ikehara.

17 recordsLinked to original sources
PubMed1993

[A case of cervico-mediastinal tuberculous lymphadenitis].

A 27-year-old female presented to our hospital because of anterior chest pain and left cervical tumor. Her chest X-ray film showed bilateral swelling of the superior mediastinum, which was composed of multiple mediastinal masses with obliteration of adjacent mediastinal fat on chest CT film. A specimen obtained from a left cervical lymph node histologically showed granuloma formation with central caseous necrosis, and the diagnosis of cervicomediastinal tuberculous lymphadenitis was therefore made. Both cervical tumor and mediastinal masses decreased in size following antituberculous chemotherapy. Mediastinal tuberculous lymphadenitis in young adults is rare. It is difficult to differentiate this condition from other mediastinal tumors, although its CT findings are characteristic.

Adult↗
PubMed1991

Residual guanosine 3',5'-bispyrophosphate synthetic activity of relA null mutants can be eliminated by spoT null mutations.

It was known previously that 1) the relA gene of Escherichia coli encodes an enzyme capable of guanosine 3',5'-bispyrophosphate (ppGpp) synthesis, 2) an uncharacterized source of ppGpp synthesis exists in relA null strains, and 3) cellular degradation of ppGpp is mainly due to a manganese-dependent ppGpp 3'-pyrophosphohydrolase encoded by the spoT gene. Here, the effects of spoT gene insertions and deletions are compared with analogous alterations in neighboring genes in the spo operon and found to be lethal in relA+ strains as well as slower growing in relAl backgrounds than delta relA hosts. Cells with null alleles in both the relA and spoT genes are found no longer to accumulate ppGpp after glucose exhaustion or after chelation of manganese ions by picolinic acid addition; the inability to form ppGpp is reversed by a minimal spoT gene on a multicopy plasmid. Strains apparently lacking ppGpp show a complex phenotype including auxotrophy for several amino acids and morphological alterations. We propose that the SpoT protein can either catalyze or control the alternative pathway of ppGpp synthesis in addition to its known role as a (p)ppGpp 3'-pyrophosphohydrolase. We favor the possibility that the SpoT protein is a bifunctional enzyme capable of catalyzing either ppGpp synthesis or degradation.

Alleles↗
PubMed1989

Characterization of the spoT gene of Escherichia coli.

The Escherichia coli spoT gene encodes a guanosine-3',5'-bispyrophosphate (ppGpp) 3'-pyrophosphohydrolase known to be responsible for cellular (ppGpp) degradation. The DNA sequence of the spoT region is presented. The spoT gene is deduced to be 702 codons long, with a probable UUG initiation codon, and a deduced mass of 79,342 daltons. Two spoT mutations (spoT202 and spoT203) have been localized to an open reading frame by complementation of function as well as by genetic marker rescue. The ability to overexpress the spoT gene is limited, but enough ppGppase activity can be made to reverse ppGpp accumulation during the stringent response to amino acid starvation. The spoT gene is located within a larger spo operon and is flanked by two smaller genes. The first gene in the operon encodes omega, a protein that copurifies with RNA polymerase (Gentry, D. R., and Burgess, R. R. (1986) Gene (Amst.) 48, 33-40). The spoT gene is the second gene in the operon; it is followed by a third open reading frame deduced to encode a protein with a mass of 25,343 daltons. Insertion of a kanamycin resistance gene in the omega gene reduces spoT gene expression as judged by lowered ppGppase activity, relA-dependent reduction of growth rate, and abolition of spoT mutant complementation activity. These effects are reversed by expression of the spoT gene, but not the omega gene, in trans. Transcription of the spo operon occurs in a clockwise direction on the E. coli chromosome and is probably directed by at least two promoters.

Alleles↗
PubMed1985

Induction of stringent response by streptomycin in Bacillus subtilis cells.

A stringent response was induced in Bacillus subtilis vegetative cells by streptomycin. This was confirmed as follows: In B. subtilis stringent cells (BR16S), stable RNA synthesis was repressed, and pppGpp and ppGpp were transiently synthesized in the presence of required amino acids and streptomycin. However, these phenomena were not observed in the isogenic relaxed strain (BR16R) under the same conditions. On the other hand, tetracyclines did not induce the response, and, moreover, the stringent response to streptomycin upon pretreatment of the stringent cells with the antibiotics was released.

Amino Acids↗
PubMed1982

Induction of Bacillus subtilis sporulation by decoyinine and the concomitant disappearance of ppGpp in vegetative cells.

Sporulation of Bacillus subtilis, growing exponentially in the presence of rapidly metabolizable nutrients, was induced by addition of decoyinine (an antibiotic inhibitor of GMP synthesis), and intracellular amounts of ppGpp were determined after 2 M formic acid extraction by polyethyleneimine (PEI)-cellulose thin-layer chromatography. Consequently, it was found that the ppGpp in vegetative cells abruptly disappeared after the addition of decoyinine. This indicates that the disappearance of ppGpp is closely correlated to the initiation of B. subtilis sporulation.

Adenosine↗
PubMed1981

Presence of guanosine 5'-diphosphate 3'-diphosphate in Bacillus subtilis vegetative cells.

Extracts of Bacillus subtilis vegetative cells with 2 M formic acid contained a large amount of a hyperphosphorylated nucleotide ("spot 4" nucleotide). The compound always comigrated with authentic guanosine 5'-diphosphate 3'-diphosphate (ppGpp) on two-dimensional polyethyleneimine (PEI)-cellulose thin-layer chromatography performed with three different solvent systems. Furthermore, all dephosphorylated 32P-labeled derivatives from the "spot 4" nucleotide comigrated on a one-dimensional PEI-cellulose plate with those from authentic ppGpp present in the same reaction mixture, when the compounds were hydrolyzed with snake venom phosphodiesterase or alkali. The level of the "spot 4" nucleotide (ppGpp) in the cell extracts was 0.14 nmol P/A660, corresponding to about one-third of the guanosine 5'-triphosphate (GTP) level and about 10% of the adenosine 5'-triphosphate (ATP) level. These results indicate that a "magic spot" nucleotide, ppGpp, is present at a high level in B. subtilis cells vegetatively growing in mNSMP.

Bacillus subtilis↗
PubMed1981

Disappearance of guanosine 5'-diphosphate 3'-diphosphate in Bacillus subtilis vegetative cells upon carbon source deprivation.

Bacillus subtilis was grown in a nutrient medium, mNSMP, and a synthetic medium, mS6(C), in which spore formation was initiated after vegetative growth and exhaustion of carbon source or glucose. The amounts of intracellular phosphorylated compounds were analyzed at intervals by 2 M formic acid extraction and polyethyleneimine (PEI)-cellulose thin-layer chromatography followed by autoradiography. A hyperphosphorylated nucleotide, guanosine 5'-diphosphate 3'-diphosphate (ppGpp), was accumulated in cells during vegetative growth in both mNSMP and mS6(C), and then the nucleotide was degraded upon initiation of sporulation in both cases. Furthermore, after the nucleotide had disappeared in cells cultivated in mS6(C) upon exhaustion of the carbon source, it could be reformed in the sporulating cells by addition of glucose to the medium. These results suggest that the ppGpp in vegetative cells may function in the regulation of B. subtilis sporulation.

Bacillus subtilis↗
PubMed1979

Properties of unprimed poly(A)-poly(U) synthesis by Caulobacter crescentus RNA polymerase.

Some properties of unprimed poly(A)-poly(U) synthesis by DNA-dependent RNA polymerase from Caulobacter crescentus were examined. The reaction required ATP and UTP as substrates and manganese as a divalent cation. Rifampicin completely inhibited the reaction at a concentration of 1 micron/ml, and the enzyme catalyzed the polymer synthesis well regardless of the presence of GTP, CTP or both. The chain length of the poly(A)-poly(U) synthesized was about one hundred base pairs, as estimated from a sedimentation velocity and the molar ratio of [3H]AMP to [gamma-32P]ATP incorporated into the poly(A)-poly(U). The reaction was dependent on the square of the enzyme concentration and the enzyme dimers formed complexes with poly(A)-poly(U) during the reaction.

Adenosine Monophosphate↗
PubMed1975

Isolation and chemcial properties of A-protein from filamentous phage Fd.

A-Protein was isolated from a purified male-specific filamentous phage fd particle. A-Protein has a molecular weight of approximately 60,000 daltons, as estimated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The amino-terminal residue was glycine as determined by the dansylation technique. Amino acid analysis showed that histidine, arginine, and cysteine, which are not contained in B-protein, are present in A-protein.

Amino Acids↗