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Biomedical subjects

M Tokunaga

Publications and source records attributed to M Tokunaga.

At least 253 records · Page 14Linked to original sources
PubMed1985

Location of the SH group of the alkali light chain on the myosin head as revealed by electron microscopy.

The location of the single cysteinyl residue of the alkali light chain on the myosin head was determined by electron microscopy. The cysteinyl residue of isolated alkali light chain 2 was biotinylated and the light chain was exchanged with that of heavy meromyosin in 4.7 M-NH4Cl. Avidin was attached to the biotin in the heavy meromyosin and the complex was rotary shadowed and observed in the electron microscope. The distance from the head-rod junction to the centre of avidin was 8(+/- 3) nm (mean value +/- standard deviation: n = 105).

Animals↗
PubMed1985

Identification of prolipoprotein signal peptidase and genomic organization of the lsp gene in Escherichia coli.

The product of the lsp gene of Escherichia coli, i.e. the prolipoprotein signal peptidase, was identified by both in vivo pulse labeling experiments using a high expression lambda PL promoter vector and by an in vitro transcription/translation coupled system. The molecular weight of prolipoprotein signal peptidase was estimated to be approximately 18,000 by its mobility on polyacrylamide gel electrophoresis and was found to be the same as that of SPase II purified from the wild-type cells. Analysis of SPase II activities in strains containing various subclones, deletion derivatives generated from plasmid pMT521, and analysis of protein products in a strain harboring an ileS-lsp-fused gene indicated that ileS and lsp genes are transcribed on the same mRNA. This was further supported by the observation that Tn5 insertions in the ileS gene resulted in a reduced expression of the lsp gene. In addition to an upstream promoter shared by the ileS and lsp genes, these analyses also revealed the presence of an internal promoter for the lsp gene within the coding region of the ileS gene.

Bacterial Outer Membrane Proteins↗
PubMed1985

Germ tube-forming cells of Candida albicans are more susceptible to clotrimazole-induced killing than yeast cells.

Yeast and germ tube-forming cells of Candida albicans were compared with respect to their susceptibility to killing induced by the imidazole antifungal clotrimazole. Cultures consisting largely of germ tube-forming cells or exclusively yeast cells were prepared by incubating cells of a germ tube-proficient strain in a proline-containing phosphate buffer at 37 degrees C or 25 degrees C, respectively. When treated with clotrimazole at 37 degrees C, the cultures of germ tube cells lost colony-forming ability much more rapidly than those of yeast cells. However, this difference was diminished in the cells preincubated at 37 degrees C but prevented from forming germ tubes by 5 mM cysteine, a suppressor of germ tube formation. In another C. albicans isolate showing a very poor capacity to form germ tubes at 37 degrees C, such a difference in killing rate was much smaller than that for the germ tube-proficient strain. Furthermore, when an isogenic pair of strains, one proficient and the other deficient in germ tube formation, were compared with each other, germ tube-forming cultures of the former were found to be more sensitive than yeast cell cultures of the latter. It is inferred from these results that the germ tube-forming cell of C. albicans is more sensitive to clotrimazole-induced killing than the yeast cell.

Candida albicans↗
PubMed1985

Juvenile secretory carcinoma and juvenile papillomatosis.

Two cases of juvenile secretory carcinoma associated with juvenile papillomatosis are reported. One patient's disease was initially diagnosed at the age of 13 and she died 12 years later with extensive metastases. The contralateral breast at autopsy showed findings indicative of juvenile papillomatosis. The second case is that of an 18-year-old girl who had multiple juvenile secretory carcinomas in the left breast associated with juvenile papillomatosis.

Adolescent↗
PubMed1984

Histologic review of breast cancer cases in survivors of atomic bombs in Hiroshima and Nagasaki, Japan.

A panel of Japanese and American pathologists reviewed existing histologic material used to study breast cancer risk among the A-bomb survivors in Hiroshima and Nagasaki, a population in which incidence studies have found a strong relationship between breast cancer risk and radiation dose. The primary charge to the panel was to define a body of confirmed cases in the Life Span Study sample of the Radiation Effects Research Foundation that would require little or no review for inclusion in future studies of breast cancer incidence. Broad agreement on histologic type was reached for 298 of 300 confirmed cases. The distribution of histologic types was, overall, similar to that seen in other studies of breast cancer in Japanese women, and did not appear to depend on dose; thus radiation-induced breast cancer appeared to be no different histologically from other breast cancer. Also, no evidence was found of variation in histologic type by city, age at exposure, age at diagnosis, or calendar time.

Adolescent↗
PubMed1984

Prolipoprotein modification and processing enzymes in Escherichia coli.

Prolipoprotein signal peptidase, a unique endopeptidase which recognizes glycyl glyceride cysteine as a cleavage site, was characterized in an in vitro assay system using purified prolipoprotein as the substrate. This enzyme did not require phospholipids for its catalytic activity and was found to be localized in the inner cytoplasmic membrane of the Escherichia coli cell envelope. Globomycin inhibited this enzyme activity in vitro with a half-maximal inhibiting concentration of 0.76 nM. Nonionic detergent, such as Nikkol or Triton X-100, was required for the in vitro activity. The optimum pH and reaction temperature of prolipoprotein signal peptidase were pH 7.9 and 37-45 degrees C, respectively. Phosphatidylglycerol:prolipoprotein glyceryl transferase (glyceryl transferase) activity was measured using [2-3H]glycerol-labeled JE5505 cell envelope and [35S]cysteine-labeled MM18 cell envelope as the donor and acceptor of glyceryl moiety, respectively. 3H and 35S dual-labeled glyceryl cysteine was identified in the product of this enzymatic reaction. The optimal pH and reaction temperature for glyceryl transferase were pH 7.8 and 37 degrees C, respectively.

Anti-Bacterial Agents↗
PubMed1984

A distinct signal peptidase for prolipoprotein in Escherichia coli.

We have previously demonstrated the modification and processing of Escherichia coli prolipoprotein (Braun's) in vitro ( Tokunaga M, Tokunaga H, Wu HC: Proc Natl Acad Sci USA 79:2255, 1982). Using this in vitro assay of prolipoprotein signal peptidase and globomycin selection, we have isolated and partially characterized an E coli mutant which contained a higher level of prolipoprotein signal peptidase activity. In contrast, the procoat protein signal peptidase activity was not increased in this mutant as compared to the wild-type strain. Furthermore, E coli strains containing cloned procoat protein signal peptidase gene were found to contain elevated levels of procoat protein signal peptidase, but normal levels of prolipoprotein signal peptidase. These two signal peptidase activities were also found to exhibit different stabilities during storage at 4 degrees C. Thus biochemical, immunological, and genetic evidence clearly indicate that prolipoprotein signal peptidase is distinct from procoat protein signal peptidase in E coli.

Anti-Bacterial Agents↗
PubMed1984

Nucleotide sequence of the Escherichia coli prolipoprotein signal peptidase (lsp) gene.

The nucleotide sequence of the prolipoprotein signal peptidase (lsp) gene has been determined. The lsp gene was found to be adjacent to the isoleucyl-tRNA synthetase ( ileS ) gene, such that the termination codon of the ileS gene overlaps with the initiation codon of lsp. These two genes are transcribed in the same direction and the major promotor for the lsp gene appears to be upstream of ileS . Identification of the lsp gene was established by amplification of prolipoprotein signal peptidase activity in strains carrying a subcloned 1.1-kilobase Stu I-Acc I fragment and was further confirmed by introducing mutational alterations in the COOH terminus of the protein that caused a decrease in prolipoprotein signal peptidase activity. The deduced amino acid sequence indicates that prolipoprotein signal peptidase contains 164 residues. Unlike most exported proteins, there is no apparent signal peptide sequence for the lsp protein. Computer-assisted secondary structure analysis of the deduced amino acid sequence identified four hydrophobic regions that share features common to transmembrane segments in integral membrane proteins.

Bacterial Outer Membrane Proteins↗
PubMed1984

Mapping of the lipoprotein signal peptidase gene (lsp).

A pBR322 plasmid which contains a fragment of Escherichia coli DNA encoding the lipoprotein signal peptidase gene was used to transform Hfr polA1 strains. Ampr transformants were used as donors in conjugation experiments, and the location of the plasmid amp gene adjacent to the chromosomal lsp gene was determined to be near the thr ara loci of the E. coli chromosome. P1 transduction experiments established that the location of the lsp gene is closely linked to that of dapB , at 0.5 to 0.6 min on the E. coli genetic map. The position of the lsp gene was further determined to be between ileS and dapB by complementation analysis of an E. coli mutant showing temperature-sensitive prolipoprotein signal peptidase activity.

Chromosome Mapping↗
PubMed1983

Isolation and characterization of an Escherichia coli clone overproducing prolipoprotein signal peptidase.

Based on the rationale that Escherichia coli cells containing increased levels of prolipoprotein signal peptidase would be highly resistant to globomycin, a specific inhibitor of the prolipoprotein signal peptidase, we have isolated a clone from the Carbon-Clarke collection, plasmid pLC3-13, which is globomycin-resistant and contains an increased level of prolipoprotein signal peptidase activity. The plasmid pMT521, a subclone of pLC3-13 in pBR322, conferred on its host cells approximately 20 times overproduction of prolipoprotein signal peptidase and an extremely high level of resistance against globomycin. The overproduced prolipoprotein signal peptidase was completely inhibited by the presence of globomycin in the in vitro assay, and the overproduced activity was found in the cell envelope fraction. Several lines of biochemical and genetic evidence suggest that the gene contained in pLC3-13 and its derivative clones is most likely the structure gene (lsp) for prolipoprotein signal peptidase.

Anti-Bacterial Agents↗