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951.
Keizo Uzu Yujiro Harada Shigetoshi Wakaki Yasuhiro Yamada 《Bioscience, biotechnology, and biochemistry》2013,77(6):388-402
Mitomycin A (C16H19O6N3) and mitomycin C (C15H18O5N4) are pigments which have the quinoid structure. When treated with aqueous ammonia, mitomycin A is converted to mitomycin C. Acid hydrolysis of mitomycin C gave three degradation products, namely, C14H15O5N4, C14H15O6N3 and C13H14O5N2. Acetylation with acetic anhydride and pyridine and methylation with methyl iodide gave monoacetyl and monomethyl derivatives of mitomycin C respectively, though diacetate of demethyl derivatives were obtained when boiled with acetic anhydride. 相似文献
952.
Haruhisa Kikuchi Yuzuru Kubohara Van Hai Nguyen Yasuhiro Katou Yoshiteru Oshima 《Bioorganic & medicinal chemistry》2013,21(15):4628-4633
Cellular slime molds are expected to have the huge potential for producing secondary metabolites including polyketides, and we have studied the diversity of secondary metabolites of cellular slime molds for their potential utilization as new biological resources for natural product chemistry. From the methanol extract of fruiting bodies of Polysphondylium filamentosum, we obtained new chlorinated benzofurans Pf-1 (4) and Pf-2 (5) which display multiple biological activities; these include stalk cell differentiation-inducing activity in the well-studied cellular slime mold, Dictyostelium discoideum, and inhibitory activities on cell proliferation in mammalian cells and gene expression in Drosophila melanogaster. 相似文献
953.
954.
Fujimoto T Tomitaka Y Abe H Tsuda S Futai K Mizukubo T 《Journal of plant physiology》2011,168(10):1084-1097
We investigated what gene(s) in the plant roots have the positive role against repressing root-knot nematode (RKN) infection. We investigated the interaction between RKN infection and gene expression in the plant roots induced by methyl jasmonate (MeJA). We focused on the induced resistance response and the duration after foliar treatment with MeJA of 0.1, 0.5, 1.0, and 5.0mM at 1, 24, 48, and 72h prior to the inoculation of RKN. As a result, the foliar treatment with MeJA at 0.5mM or higher concentrations significantly reduced the infection of RKN in plants and the effect lasted for about 1 week. The repressing effect on RKN population declined to the lowest level in two weeks after MeJA treatment. The expression of proteinase inhibitors (PIs) and multicystatin (MC) were induced while the repressing effect on RKN was valid and a negative correlation was found between the expression of PIs or MC and RKN infection. In addition, when tomato plants no longer expressing MC and PIs were treated again with MeJA, the repressing effect revived. These phenomena appeared to be regardless of the existence of Mi-genes or isolate of RKN. Our results indicate that the expression level of MC and PIs may be effective as marker genes for estimating the induced resistance response against RKN infection. 相似文献
955.
Yasuhiro Kubota Toshihide Hirao Shin‐jiro Fujii Masashi Murakami 《Journal of Biogeography》2011,38(5):1006-1008
Quantifying the roles of historical versus contemporary constraints in determining species diversity is a central issue in island biogeography, and the phylogenetic beta diversity between islands is an essential measure specifying the influence of historical barriers on insular assemblages. In this study, using phylogenetic information for 513 tree species on 26 islands in the subtropical Ryukyu Archipelago, phylogenetic beta diversity between islands was calculated, and effects of historical factors (gaps as surrogate measures of historical barriers) and current ones (distance, area and elevation) on the phylogenetic structure of tree assemblages were examined. The pattern of phylogenetic beta diversity demonstrated that the Tokara Gap and geographical distance were consistently important for characterizing tree assemblages in the Ryukyus relative to other historical and current factors, which suggests that the Tokara Gap and distance‐limited dispersal from the two adjacent source islands have left a deep imprint on the phylogenetic structure of the current tree flora of the islands. 相似文献
956.
Asamizu S Shiro Y Igarashi Y Nagano S Onaka H 《Bioscience, biotechnology, and biochemistry》2011,75(11):2184-2193
The diversity of indolocarbazole natural products results from the differences in oxidation states of the pyrroline ring moiety. In the biosynthetic pathways for staurosporine and rebeccamycin, two homologous enzymes having 64% identity, StaC and RebC, are responsible for the selective production of K252c, which has one oxo group at the pyrroline ring, and arcyriaflavin A, which has two. Although StaC has a FAD-binding motif, most StaC molecules do not contain FAD, and the protein cannot be reconstituted with FAD in vitro. In this study, we mutated Ala-118 in StaC by replacing a glutamine that is conserved in FAD monooxygenases, resulting in increased FAD content as well as catalytic activity. In addition, mutations around the substrate-binding sites of StaC and RebC can change the product selectivity. Specifically, StaC-N244R-V246T and RebC-F216V-R239N mutants produced substantial amounts of arcyriaflavin A and K252c, respectively. 相似文献
957.
Hiramatsu Y Hosono A Konno T Nakanishi Y Muto M Suyama A Hachimura S Sato R Takahashi K Kaminogawa S 《Cytotechnology》2011,63(3):307-317
We have investigated the immunomodulatory mechanisms of Bifidobacterium pseudocatenulatum JCM7041 (Bp) as model of probiotics following oral administration to mice. This study was conducted with the aim of clarifying
the mechanism of immunomodulation induced by oral administration of probiotic bacteria through elucidation of the detailed
mechanism of transfer of orally administered bacterial cells within the body and the interaction between bacterial cells and
cells of the immune tissues. We observed the localization of Bp in mice following oral administration, showing that Bp was
surrounded by CD11c+ cells in Peyer’s patches (PP) and cecal patches (CP). These results indicated that Bp might induce CD11c+ cell-mediated immune responses directly. Furthermore, IL-10 and IL-12p40 production by Thy1.2− cells, including CD11c+ cells, increased significantly. Production of IL-10 and IL-12p40 by bone marrow-derived dendritic cells (BMDC) was significantly
increased by Bp stimulation. These results suggest that oral administration of Bp induces immune responses directly following
capture by CD11c+ dendritic cells (DCs). Subsequently, we observed oral administration of Bp for 1 week induced IgA and IgA-associated cytokine
production by CP and PP cells, suggesting that Bp induced DC-mediated immune responses on CP as well as PP. 相似文献
958.
Hoshino Y Chiba K Ishino K Fukai T Igarashi Y Yazawa K Mikami Y Ishikawa J 《Journal of bacteriology》2011,193(2):441-448
We identified the biosynthetic gene clusters of the siderophore nocobactin NA. The nbt clusters, which were discovered as genes highly homologous to the mycobactin biosynthesis genes by the genomic sequencing of Nocardia farcinica IFM 10152, consist of 10 genes separately located at two genomic regions. The gene organization of the nbt clusters and the predicted functions of the nbt genes, particularly the cyclization and epimerization domains, were in good agreement with the chemical structure of nocobactin NA. Disruptions of the nbtA and nbtE genes, respectively, reduced and abolished the productivity of nocobactin NA. The heterologous expression of the nbtS gene revealed that this gene encoded a salicylate synthase. These results indicate that the nbt clusters are responsible for the biosynthesis of nocobactin NA. We also found putative IdeR-binding sequences upstream of the nbtA, -G, -H, -S, and -T genes, whose expression was more than 10-fold higher in the low-iron condition than in the high-iron condition. These results suggest that nbt genes are regulated coordinately by IdeR protein in an iron-dependent manner. The ΔnbtE mutant was found to be impaired in cytotoxicity against J774A.1 cells, suggesting that nocobactin NA production is required for virulence of N. farcinica. 相似文献
959.
960.
Imamura J Suzuki Y Gonda K Roy CN Gatanaga H Ohuchi N Higuchi H 《The Journal of biological chemistry》2011,286(12):10581-10592
The mechanism by which HIV-1-Tat protein transduction domain (TatP) enters the cell remains unclear because of an insufficient understanding of the initial kinetics of peptide entry. Here, we report the successful visualization and tracking of TatP molecular kinetics on the cell surface with 7-nm spatial precision using quantum dots. Strong cell binding was only observed with a TatP valence of ≥8, whereas monovalent TatP binding was negligible. The requirement of the cell-surface heparan sulfate (HS) chains of HS proteoglycans (HSPGs) for TatP binding and intracellular transport was demonstrated by the enzymatic removal of HS and simultaneous observation of two individual particles. Multivalent TatP induces HSPG cross-linking, recruiting activated Rac1 to adjacent lipid rafts and thereby enhancing the recruitment of TatP/HSPG to actin-associated microdomains and its internalization by macropinocytosis. These findings clarify the initial binding mechanism of TatP to the cell surface and demonstrate the importance of TatP valence for strong surface binding and signal transduction. Our data also shed light on the ability of TatP to exploit the machinery of living cells, using HSPG signaling to activate Rac1 and alter TatP mobility and internalization. This work should guide the future design of TatP-based peptides as therapeutic nanocarriers with efficient transduction. 相似文献