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排序方式: 共有434条查询结果,搜索用时 31 毫秒
31.
The current mechanistic model of chaperonin-assisted protein folding assumes that the substrate protein in the cage, formed by GroEL central cavity capped with GroES, is isolated from outside and exists as a free polypeptide. However, using ATPase-deficient GroEL mutants that keep GroES bound, we found that, in the rate-limiting intermediate of a chaperonin reaction, the unfolded polypeptide in the cage partly protrudes through a narrow space near the GroEL/GroES interface. Then, the entire polypeptide is released either into the cage or to the outside medium. The former adopts a native structure very rapidly and the latter undergoes spontaneous folding. Partition of the in-cage folding and the escape varies among substrate proteins and is affected by hydrophobic interaction between the polypeptide and GroEL cavity wall. The ATPase-active GroEL with decreased in-cage folding produced less of a native model substrate protein in Escherichia coli cells. Thus, the polypeptide in the critical GroEL-GroES complex is neither free nor completely confined in the cage, but it is interacting with GroEL's apical region, partly protruding to outside. 相似文献
32.
Mariko Ishibashi Takaji Wakita 《Biochemical and biophysical research communications》2010,392(3):397-402
We found the 2′,5′-oligoadenylate synthetase-like (OASL) gene to be significantly elevated by high virus loads in human liver infected with hepatitis C virus (HCV). Here, we determined whether OASL inhibited HCV replication using an in vitro system. We constructed three expression vectors of OASL to produce isoform a (OASLa), isoform b (OASLb), and the C-terminal ubiquitin-like domain of isoform a (Ub). When Huh7 JFH-1 HCV replicon cells were separately transfected with these three vectors, colony formation of HCV-replicating cells was inhibited by 95%, 94%, and 65%, respectively. Both OASLa and OASLb were also inhibitory for cells as well as the virus because colony formation of OASL-producing cells was reduced to 41% and 8%, respectively. Stable Huh7 clones producing each of the three OASLs were established and assessed for their inhibition of HCV replication using luciferase reporter gene-containing JFH-1 replicon RNA. HCV replication was inhibited by 50-90% in several stable OASL clones. Association analysis in six Ub clones expressing different levels of Ub mRNA showed that the degree of inhibition of HCV replication was significantly associated with the amount of Ub present. In conclusion, OASL possesses two domains with HCV inhibitory activity. The N-terminal OAS-homology domain without OAS activity is inhibitory for cell growth as well as HCV replication, whereas C-terminal Ub is inhibitory only for HCV replication. Therefore, OASLa, a major isoform of this molecule induced in human liver, may mediate anti-HCV activity through two different domains. 相似文献
33.
Ismiarni Komala Takuya Ito Fumihiro Nagashima Yasuyuki Yagi Masatoshi Kawahata Kentaro Yamaguchi Yoshinori Asakawa 《Phytochemistry》2010,71(11-12):1387-1394
Cembrane-type diterpenoids, 13,18,20-epi-iso-chandonanthone (1) and (8E)-4α-acetoxy-12α,13α-epoxycembra-1(15),8-diene (2), two fusicoccane-type diterpenoids, fusicoauritone 6α-methyl ether (3) and 6β,10β-epoxy-5β-hydroxyfusicocc-2-ene (4) and a zierane sesquiterpene γ-lactone, chandolide (5) were isolated from the Tahitian liverwort Chandonanthus hirtellus (Web.) Mitt., together with eight known diterpenoids, chandonanthine (6), fusicogigantone A (7), fusicogigantone B (8), fusicogigantepoxide (9), anadensin (10), fusicoauritone (11), ent-verticillol (12) and ent-epi-verticillol (13). Their structures were established by a combination of extensive NMR spectroscopy and/or X-ray crystallographic analyses. Compounds 1, 5 and 10 showed weak cytotoxic activity against HL-60. Compound 3 also indicated weak cytotoxic activity against KB cell lines. 相似文献
34.
Sakane I Hongo K Motojima F Murayama S Mizobata T Kawata Y 《Journal of molecular biology》2007,367(4):1171-1185
In order to understand how inter-subunit association stabilizes oligomeric proteins, a single polypeptide chain variant of heptameric co-chaperonin GroES (tandem GroES) was constructed from Escherichia coli heptameric GroES by linking consecutively the C-terminal of one subunit to the N-terminal of the adjacent subunit with a small linker peptide. The tandem GroES (ESC7) showed properties similar to wild-type GroES in structural aspects and co-chaperonin activity. In unfolding and refolding equilibrium experiments using guanidine hydrochloride (Gdn-HCl) as a denaturant at a low protein concentration (50 microg ml(-1)), ESC7 showed a two-state transition with a greater resistance toward Gdn-HCl denaturation (Cm=1.95 M) compared to wild-type GroES (Cm=1.1 M). ESC7 was found to be about 10 kcal mol(-1) more stable than the wild-type GroES heptamer at 50 microg ml(-1). Kinetic unfolding and refolding experiments of ESC7 revealed that the increased stability was mainly attributed to a slower unfolding rate. Also a transient intermediate was detected in the refolding reaction. Interestingly, at the physiological GroES concentration (>1 mg ml(-1)), the free energy of unfolding for GroES heptamer exceeded that for ESC7. These results showed that at low protein concentrations (<1 mg ml(-1)), the covalent linking of subunits contributes to the stability but also complicates the refolding kinetics. At physiological concentrations of GroES, however, the oligomeric state is energetically preferred and the advantages of covalent linkage are lost. This finding highlights a possible advantage in transitioning from multi-domain proteins to oligomeric proteins with small subunits in order to improve structural and kinetic stabilities. 相似文献
35.
Amino acid substitutions in the s2 region enhance severe acute respiratory syndrome coronavirus infectivity in rat angiotensin-converting enzyme 2-expressing cells
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Fukushi S Mizutani T Sakai K Saijo M Taguchi F Yokoyama M Kurane I Morikawa S 《Journal of virology》2007,81(19):10831-10834
To clarify the molecular basis of severe acute respiratory syndrome coronavirus (SARS-CoV) adaptation to different host species, we serially passaged SARS-CoV in rat angiotensin-converting enzyme 2 (ACE2)-expressing cells. After 15 passages, the virus (Rat-P15) came to replicate effectively in rat ACE2-expressing cells. Two amino acid substitutions in the S2 region were found on the Rat-P15 S gene. Analyses of the infectivity of the pseudotype-bearing S protein indicated that the two substitutions in the S2 region, especially the S950F substitution, were responsible for efficient infection. Therefore, virus adaptation to different host species can be induced by amino acid substitutions in the S2 region. 相似文献
36.
37.
Characterization of a broadly reactive monoclonal antibody against norovirus genogroups I and II: recognition of a novel conformational epitope
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Shiota T Okame M Takanashi S Khamrin P Takagi M Satou K Masuoka Y Yagyu F Shimizu Y Kohno H Mizuguchi M Okitsu S Ushijima H 《Journal of virology》2007,81(22):12298-12306
Norovirus, which belongs to the family Caliciviridae, is one of the major causes of nonbacterial acute gastroenteritis in the world. The main human noroviruses are of genogroup I (GI) and genogroup II (GII), which were subdivided further into at least 15 and 18 genotypes (GI/1 to GI/15 and GII/1 to GII/18), respectively. The development of immunological diagnosis for norovirus had been hindered by the antigen specificity of the polyclonal antibody. Therefore, several laboratories have produced broadly reactive monoclonal antibodies, which recognize the linear GI and GII cross-reactive epitopes or the conformational GI-specific epitope. In this study, we characterized the novel monoclonal antibody 14-1 (MAb14-1) for further development of the rapid immunochromatography test. Our results demonstrated that MAb14-1 could recognize 15 recombinant virus-like particles (GI/1, 4, 8, and 11 and GII/1 to 7 and 12 to 15) and showed weak affinity to the virus-like particle of GI/3. This recognition range is the broadest of the existing monoclonal antibodies. The epitope for MAb14-1 was identified by fragment, sequence, structural, and mutational analyses. Both terminal antigenic regions (amino acid positions 418 to 426 and 526 to 534) on the C-terminal P1 domain formed the conformational epitope and were in the proximity of the insertion region (positions 427 to 525). These regions contained six amino acids responsible for antigenicity that were conserved among genogroup(s), genus, and Caliciviridae. This epitope mapping explained the broad reactivity and different titers among GI and GII. To our knowledge, we are the first group to identify the GI and GII cross-reactive monoclonal antibody, which recognizes the novel conformational epitope. From these data, MAb14-1 could be used further to develop immunochromatography. 相似文献
38.
Upregulation of indoleamine 2,3-dioxygenase in hepatitis C virus infection 总被引:1,自引:0,他引:1
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Larrea E Riezu-Boj JI Gil-Guerrero L Casares N Aldabe R Sarobe P Civeira MP Heeney JL Rollier C Verstrepen B Wakita T Borrás-Cuesta F Lasarte JJ Prieto J 《Journal of virology》2007,81(7):3662-3666
Indoleamine 2,3-dioxygenase (IDO) is induced by proinflammatory cytokines and by CTLA-4-expressing T cells and constitutes an important mediator of peripheral immune tolerance. In chronic hepatitis C, we found upregulation of IDO expression in the liver and an increased serum kynurenine/tryptophan ratio (a reflection of IDO activity). Huh7 cells supporting hepatitis C virus (HCV) replication expressed higher levels of IDO mRNA than noninfected cells when stimulated with gamma interferon or when cocultured with activated T cells. In infected chimpanzees, hepatic IDO expression decreased in animals that cured the infection, while it remained high in those that progressed to chronicity. For both patients and chimpanzees, hepatic expression of IDO and CTLA-4 correlated directly. Induction of IDO may dampen T-cell reactivity to viral antigens in chronic HCV infection. 相似文献
39.
Mineralization process during acellular cementogenesis in rat molars: a histochemical and immunohistochemical study using fresh-frozen sections 总被引:2,自引:2,他引:0
Yamamoto T Domon T Takahashi S Anjuman KA Fukushima C Wakita M 《Histochemistry and cell biology》2007,127(3):303-311
This study was designed to detect tissue non-specific alkaline phosphatase (TNSALP) by Azo-dye staining, calcium by glyoxal
bis (2-hydroxyanil) (GBHA) staining, bone sialoprotein (BSP) and osteopontin (OPN) by immunoperoxidase staining in developing
rat molars, and also to discuss the mineralization process during acellular cementogenesis. To restrain a reduction in histochemical
and immunohistochemical reactions, fresh-frozen undemineralized sections were prepared. Where the epithelial sheath was intact,
TNSALP reaction was observed in the dental follicle, but not in the epithelial sheath. With the onset of dentin mineralization,
the BSP- and OPN-immunoreactive, initial cementum layer appeared. At this point, cementoblasts had shown intense TNSALP reaction
and GBHA reactive particles (=calcium-GBHA complex) appeared on the root surface. With further development, the reaction of
TNSALP and GBHA became weak on the root surface. Previous studies have shown that the initial cementum is fibril-poor and
that matrix vesicles and calciferous spherules appear on the root surface only during the initial cementogenesis. The findings
mentioned above suggest that: during the initial cementogenesis, cementoblasts release matrix vesicles which result in calciferous
spherules, corresponding to the GBHA reactive particles. The calciferous spherules trigger the mineralization of the initial
cementum. After principal fiber attachment, mineralization advances along collagen fibrils without matrix vesicles. 相似文献
40.