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排序方式: 共有903条查询结果,搜索用时 187 毫秒
1.
A theory of the double layer interaction regulated by the Donnan potential between two ion-penetrable membranes in an electrolyte solution developed previously by Ohshima and Kondo is extended to the case in which the membranes consist of many layers having different thickness and densities of membrane-fixed charges. The interaction force is found to be determined mainly by the contributions from layers located within the depth of 1/kappa (kappa, Debye-Hückel parameter) from the membrane surface. It is also predicted that the interaction force may alter its sign with changing electrolyte concentration. 相似文献
2.
U6 small nuclear RNA (U6 snRNA) is one of the spliceosomal RNAs essential for pre-mRNA splicing. Highly conserved region of U6 snRNA shows a structural similarity with the catalytic center of the negative strand of the satellite RNA of tobacco ring spot virus [(-)sTRSV], supporting the hypothesis that U6 snRNA has a catalytic role in pre-mRNA splicing. To test this hypothesis, we examined in vitro whether synthetic RNAs consisting of the sequence of the highly conserved region of U6 snRNA or various chimeric RNAs between the U6 region and the catalytic center of (-)sTRSV could cleave a substrate RNA that can partially base-pair with them and has a GU sequence between the pairing regions. Chimeric RNAs with 70 to 83% sequence identity with the conserved region of S. pombe U6 snRNA cleaved the substrate RNA at the 5' side of the GU sequence. In addition, we found that the highly conserved region of U6 snRNA is similar in structure to the catalytic core region of the group I self-splicing intron in cyanobacteria. These results support the hypothesis that U6 snRNA catalyzes the pre-mRNA splicing reaction and U6 snRNA may originate from the catalytic domain of an ancient self-splicing intron. 相似文献
3.
Thermostable phenylalanine dehydrogenase of Thermoactinomyces intermedius: cloning, expression, and sequencing of its gene 总被引:4,自引:0,他引:4
The gene encoding the thermostable phenylalanine dehydrogenase [EC 1.4.1.-] of a thermophile, Thermoactinomyces intermedius, was cloned and its complete DNA sequence was determined. The phenylalanine dehydrogenase gene (pdh) consists of 1,098 nucleotides and encodes 366 amino acid residues corresponding to the subunit (Mr 41,000) of the hexameric enzyme. The amino acid sequence deduced from the nucleotide sequence of the pdh gene of T. intermedius was 56.0 and 42.1% homologous to those of the phenylalanine dehydrogenases of Bacillus sphaericus and Sporosarcina ureae, respectively. It shows 47.5% homology to that of the thermostable leucine dehydrogenase from B. stearothermophilus. The pdh gene was highly expressed in E. coli JM109, the amount of phenylalanine dehydrogenase produced amounting up to about 8.3% of that of the total soluble protein. We purified the enzyme to homogeneity from transformant cells in a day, with a 58% recovery. 相似文献
4.
Acrosomal ATPase in starfish and bivalve mollusk spermatozoa 总被引:1,自引:0,他引:1
ATPase activity was found in acrosomes of starfish and bivalve mollusk spermatozoa, using a cytochemical method with electron microscopy. The activity was located in central material of the starfish acrosome and in material lining the acrosomal membrane of the Mytilus acrosome, as well as in the basal part of the starfish acrosome. The ATPase activity in the former material was preferably activated by Ca2+, while that in the starfish basal material was preferably activated by Mg2+. Both types of activity persisted during and after the acrosome reaction. ATPase activity was also observed in the region of the axial filament complex of the flagella, in centrioles and in a basal matrix. ATPase in the acrosome also hydrolysed other nucleoside triphosphates. However, there was no detectable phosphatase activity, and little pyrophosphatase or 5′-nucleotidase activity. Evidence was obtained that adenylate kinase may be included in the acrosome. A possible role of the ATPase activity in the acrosome reaction is discussed. 相似文献
5.
Kenichi Ikeda Toshiaki Nakajima Yumiko Yamamoto Nami Takano Tomofumi Tanaka Hironobu Kikuchi Gaku Oguri Toshihiro Morita Fumitaka Nakamura Issei Komuro 《Cell calcium》2013
Expression of transient receptor potential canonical channels (TRPC) and the effects of transforming growth factor-β1 (TGF-β1) on Ca2+ signals and fibroblast proliferation were investigated in human cardiac fibroblasts. The conventional and quantitative real-time RT-PCR, western blot, immunocytochemical analysis, and intracellular Ca2+ concentration [Ca2+]i measurement were applied. Cell proliferation and cell cycle progression were assessed using MTT assays and fluorescence activated cell sorting. Human cardiac fibroblasts have the expression of TRPC1,3,4,6 mRNA and proteins. 1-oleoyl-2-acetyl-sn-glycerol (OAG) and thapsigargin induced extracellular Ca2+-mediated [Ca2+]i rise. siRNA for knock down of TRPC6 reduced OAG-induced Ca2+ entry. Hyperforin as well as angiotensin II (Ang II) induced Ca2+ entry. KB-R7943, a reverse-mode Na+/Ca2+ exchanger (NCX) inhibitor, and/or replacement of Na+ with NMDG+ inhibited thapsigargin-, OAG- and Ang II-induced Ca2+ entry. Treatment with TGF-β1 increased thapsigargin-, OAG- and Ang II-induced Ca2+ entry with an enhancement of TRPC1,6 protein expression, suppressed by KB-R7943. TGF-β1 and AngII promoted cell cycle progression from G0/G1 to S/G2/M and cell proliferation. A decrease of the extracellular Ca2+ and KB-R7943 suppressed it. Human cardiac fibroblasts contain several TRPC-mediated Ca2+ influx pathways, which activate the reverse-mode NCX. TGF-β1 enhances the Ca2+ influx pathways requiring Ca2+ signals for its effect on fibroblast proliferation. 相似文献
6.
Induced penetration resistance is triggered by failed penetration attempts of nonpathogenic fungi. The resistance mechanism is an important nonhost reaction in plants that can block the invasion of filamentous pathogens such as fungi and oomycetes. However, it remains unclear whether the mechanical stimuli accompanying fungal penetration play a role in induced penetration resistance, whereas the perforation of the cell wall may provide significant stimuli to plant cells. Here, we used microneedles or biolistic bombardment to mimic fungal penetration pegs and a micromanipulation transfer technique of the bio-probe, a germling of Blumeria graminis hordei, to the wounded cells to demonstrate that microwounds derived from fungal penetration attempts may trigger induced penetration resistance in plant cells. When preinoculated with the nonpathogenic fungi Erysiphe pisi and Colletotrichum orbiculare, which were unable to penetrate a barley cell, the penetration of a bio-probe that was transferred by micromanipulation onto the same cell was completely blocked. Fungal penetration was essential to the triggering of induced penetration resistance because a penetration-peg-defective mutant of C. orbiculare completely lacked the ability to trigger resistance. The artificial microwounds significantly, but not completely, blocked the penetration of the bio-probe. Treatment with the actin polymerization inhibitor cytochalasin A or expression of the actin depolymerizing protein HvPro1 caused complete ablation of the induced penetration resistance triggered by either failed fungal penetration or artificial microwounds. These results strongly suggest that microwounding may trigger actin-dependent induced penetration resistance. Manipulation of induced penetration resistance may be a promising target to improve basic disease resistance in plants. 相似文献
7.
Akio Kobayashi Kyohei Yamashita Kohei Ohshima Izuru Yamamoto 《Bioscience, biotechnology, and biochemistry》2013,77(12):1961-1965
Allethrin-(E)-Ol (IV), allethrin-(E)-al (V) and allethrin-(E)-acid (VI), the metabolites of allethrin (III) in the insect body, were synthesized. Their low toxicities to houseflies seem to support the hypothesis that they are products of the detoxication process of allethrin. 相似文献
8.
Ryushi Kawakami Haruhiko Sakuraba Toshihisa Ohshima 《Bioscience, biotechnology, and biochemistry》2013,77(12):2045-2050
We previously found a very large NAD-dependent glutamate dehydrogenase with approximately 170?kDa subunit from Janthinobacterium lividum (Jl-GDH) and predicted that GDH reaction occurred in the central domain of the subunit. To gain further insights into the role of the central domain, several single point mutations were introduced. The enzyme activity was completely lost in all single mutants of R784A, K810A, K820A, D885A, and S1142A. Because, in sequence alignment analysis, these residues corresponded to the residues responsible for glutamate binding in well-known small GDH with approximately 50?kDa subunit, very large GDH and well-known small GDH may share the same catalytic mechanism. In addition, we demonstrated that C1141, one of the three cysteine residues in the central domain, was responsible for the inhibition of enzyme activity by HgCl2, and HgCl2 functioned as an activating compound for a C1141T mutant. At low concentrations, moreover, HgCl2 was found to function as an activating compound for a wild-type Jl-GDH. This suggests that the mechanism for the activation is entirely different from that for the inhibition. 相似文献
9.
Takahito Tamai Osamu Yamaguchi Shungo Hikoso Toshihiro Takeda Manabu Taneike Takafumi Oka Jota Oyabu Tomokazu Murakawa Hiroyuki Nakayama Yoshihiro Uno Kyoji Horie Kazuhiko Nishida Nahum Sonenberg Ajay M. Shah Junji Takeda Issei Komuro Kinya Otsu 《The Journal of biological chemistry》2013,288(14):10176-10187
Cardiomyocytes proliferate during fetal life but lose their ability to proliferate soon after birth and further increases in cardiac mass are achieved through an increase in cell size or hypertrophy. Mammalian target of rapamycin complex 1 (mTORC1) is critical for cell growth and proliferation. Rheb (Ras homologue enriched in brain) is one of the most important upstream regulators of mTORC1. Here, we attempted to clarify the role of Rheb in the heart using cardiac-specific Rheb-deficient mice (Rheb−/−). Rheb−/− mice died from postnatal day 8 to 10. The heart-to-body weight ratio, an index of cardiomyocyte hypertrophy, in Rheb−/− was lower than that in the control (Rheb+/+) at postnatal day 8. The cell surface area of cardiomyocytes isolated from the mouse hearts increased from postnatal days 5 to 8 in Rheb+/+ mice but not in Rheb−/− mice. Ultrastructural analysis indicated that sarcomere maturation was impaired in Rheb−/− hearts during the neonatal period. Rheb−/− hearts exhibited no difference in the phosphorylation level of S6 or 4E-BP1, downstream of mTORC1 at postnatal day 3 but showed attenuation at postnatal day 5 or 8 compared with the control. Polysome analysis revealed that the mRNA translation activity decreased in Rheb−/− hearts at postnatal day 8. Furthermore, ablation of eukaryotic initiation factor 4E-binding protein 1 in Rheb−/− mice improved mRNA translation, cardiac hypertrophic growth, sarcomere maturation, and survival. Thus, Rheb-dependent mTORC1 activation becomes essential for cardiomyocyte hypertrophic growth after early postnatal period. 相似文献
10.
Kiyoshi Migita Toru Arai Naoki Ishizuka Yuka Jiuchi Yasuharu Sasaki Yasumori Izumi Tetsuyuki Kiyokawa Eiichi Suematsu Tomoya Miyamura Hiroshi Tsutani Yojiro Kawabe Ryutaro Matsumura Shunsuke Mori Shiro Ohshima Shigeru Yoshizawa Kenji Kawakami Yasuo Suenaga Hideo Nishimura Toyohiko Sugimoto Hiroaki Iwase Hideyuki Sawada Haruhiro Yamashita Shigeyuki Kuratsu Fumitaka Ogushi Masaharu Kawabata Toshihiro Matsui Hiroshi Furukawa Seiji Bito Shigeto Tohma 《PloS one》2013,8(11)