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981.
Vince JE Wong WW Khan N Feltham R Chau D Ahmed AU Benetatos CA Chunduru SK Condon SM McKinlay M Brink R Leverkus M Tergaonkar V Schneider P Callus BA Koentgen F Vaux DL Silke J 《Cell》2007,131(4):682-693
XIAP prevents apoptosis by binding to and inhibiting caspases, and this inhibition can be relieved by IAP antagonists, such as Smac/DIABLO. IAP antagonist compounds (IACs) have therefore been designed to inhibit XIAP to kill tumor cells. Because XIAP inhibits postmitochondrial caspases, caspase 8 inhibitors should not block killing by IACs. Instead, we show that apoptosis caused by an IAC is blocked by the caspase 8 inhibitor crmA and that IAP antagonists activate NF-kappaB signaling via inhibtion of cIAP1. In sensitive tumor lines, IAP antagonist induced NF-kappaB-stimulated production of TNFalpha that killed cells in an autocrine fashion. Inhibition of NF-kappaB reduced TNFalpha production, and blocking NF-kappaB activation or TNFalpha allowed tumor cells to survive IAC-induced apoptosis. Cells treated with an IAC, or those in which cIAP1 was deleted, became sensitive to apoptosis induced by exogenous TNFalpha, suggesting novel uses of these compounds in treating cancer. 相似文献
982.
Rink R Wierenga J Kuipers A Kluskens LD Driessen AJ Kuipers OP Moll GN 《Applied and environmental microbiology》2007,73(6):1792-1796
Nisin is a pentacyclic peptide antibiotic produced by some Lactococcus lactis strains. Nisin contains dehydroresidues and thioether rings that are posttranslationally introduced by a membrane-associated enzyme complex, composed of a serine and threonine dehydratase NisB and the cyclase NisC. In addition, the transporter NisT is necessary for export of the modified peptide. We studied the potential of L. lactis expressing NisB and NisT to produce peptides whose serines and threonines are dehydrated. L. lactis containing the nisBT genes and a plasmid coding for a specific leader peptide fusion construct efficiently produced peptides with a series of non-naturally occurring multiple flanking dehydrobutyrines. We demonstrated NisB-mediated dehydration of serines and threonines in a C-terminal nisin(1-14) extension of nisin, which implies that also residues more distant from the leader peptide than those occurring in prenisin or any other lantibiotic can be modified. Furthermore, the feasibility and efficiency of generating a library of peptides containing dehydroresidues were demonstrated. In view of the particular shape and reactivity of dehydroamino acids, such a library provides a novel source for screening for peptides with desired biological and physicochemical properties. 相似文献
983.
984.
Biosurfactant production and surface translocation are regulated by PlcR in Bacillus cereus ATCC 14579 under low-nutrient conditions 总被引:1,自引:0,他引:1
Hsueh YH Somers EB Lereclus D Ghelardi E Wong AC 《Applied and environmental microbiology》2007,73(22):7225-7231
Bacillus cereus ATCC 14579 can respond to nutrient changes by adopting different forms of surface translocation. The B. cereus ATCC 14579 DeltaplcR mutant, but not the wild type, formed dendritic (branched) patterns on EPS [a low-nutrient medium that contains 7.0 g K(2)HPO(4), 3.0 g KH(2)PO(4), 0.1 g MgSO(4).7H(2)O, 0.1 g (NH(4))(2)SO(4), 0.01 g CaCl(2), 0.001 g FeSO(4), 0.1 g NaCl, 1.0 g glucose, and 125 mg yeast extract per liter] containing 0.7% agar. The dendritic patterns formed by sliding translocation of nonflagellated cells are enhanced under low-nutrient conditions and require sufficient production of a biosurfactant, which appears to be repressed by PlcR. The wild-type and complemented strains failed to slide on the surface of EPS agar because of the production of low levels of biosurfactant. Precoating EPS agar surfaces with surfactin (a biosurfactant produced by Bacillus subtilis) or biosurfactant purified from the DeltaplcR mutant rescued the ability of the wild-type and complemented strains to slide. When grown on a nutrient-rich medium like Luria-Bertani agar, both the wild-type and DeltaplcR mutant strains produced flagella. The wild type was hyperflagellated and elongated and exhibited swarming behavior, while the DeltaplcR mutant was multiflagellated and the cells often formed long chains but did not swarm. Thin-layer chromatography and mass spectrometry analyses suggested that the biosurfactant purified from the DeltaplcR mutant was a lipopeptide and had a mass of 1,278.1722 (m/z). This biosurfactant has hemolytic activity and inhibited the growth of several gram-positive bacteria. 相似文献
985.
Arsenic trioxide and neuroblastoma cytotoxicity 总被引:2,自引:0,他引:2
Pettersson HM Karlsson J Pietras A Øra I Påhlman S 《Journal of bioenergetics and biomembranes》2007,39(1):35-41
The majority of aggressive forms of the childhood tumor neuroblastoma can with current treatment protocols not be cured and
possess a major challenge in pediatric oncology. After initial rounds of chemotherapy, surgery and irradiation, which in most
cases result in tumor regression, these aggressive neuroblastomas relapse and frequently develop drug resistance. As approximately
50% of the children with neuroblastoma have an aggressive form, there is a compelling demand for new treatment strategies.
Arsenic trioxide has the capacity to kill multidrug-resistant neuro-blastoma cells in vitro and in vivo and the drug is currently being evaluated in clinical trials. In this report we discuss the background to the use of arsenic
trioxide in cancer therapy and the currently known mechanisms by which arsenic trioxide kills human neuroblastoma cells. 相似文献
986.
To elucidate the role of low molecular weight chelators in long-distance root-to-shoot transport of heavy metals in Indian
mustard, an “off-line” size exclusion high-performance liquid chromatography–graphite furnace atomic absorption spectrometry
was developed to investigate heavy metals associated with low molecular weight chelators in xylem saps of Indian mustard (Brassica juncea). The size exclusion chromatogram presented only the peaks with molecular weight for all xylem saps and directly indicated
the long-distance transport of phytochelatins (PCs) of Indian mustard under Cd stress. In the absence of Cd stress, only organic
acids and inorganic anions participated in the long-distance transport of Cd, but organic acids, inorganic anions, glutathione
(GSH), and cysteine might relate to the long-distance transport of Cu or Zn. In the presence of Cd stress, PCs were induced,
and Cd ions in xylem saps were associated with the induced PCs. As the Cd levels in nutrient solution increased, more Cd in
xylem saps adopted the form of PC–Cd. Although PCs might participate in the long-distance transport of Cd under Cd stress,
the majority of Cd was still transported by organic acids and inorganic anions in xylem vessels. Moreover, results indicated
the existence of complexation competition for GSH and cysteine between Cd and Cu (or Zn) and complexation competition for
Cd between PCs and GSH (or cysteine) in xylem vessels. Our work might be very useful for understanding the mechanism of long-distance
transport of heavy metals in hyperaccumulator. 相似文献
987.
Jeffrey Tze-Fei Wong 《Origins of life and evolution of the biosphere》2007,37(4-5):403-408
The coevolution theory proposes that primordial proteins consisted only of those amino acids readily obtainable from the prebiotic
environment, representing about half the twenty encoded amino acids of today, and the missing amino acids entered the system
as the code expanded along with pathways of amino acid biosynthesis. The isolation of genetic code mutants, and the antiquity
of pretran synthesis revealed by the comparative genomics of tRNAs and aminoacyl-tRNA synthetases, have combined to provide
a rigorous proof of the four fundamental tenets of the theory, thus solving the riddle of the structure of the universal genetic
code.
Presented at: International School of Complexity – 4th Course: Basic Questions on the Origins of Life; “Ettore Majorana” Foundation and Centre for Scientific Culture, Erice, Italy, 1–6 October 2006. 相似文献
988.
Although Pteris vittata L. and Sedum alfredii Hance have been identified as an As hyperaccumulator and a Zn/Cd hyperaccumulator, respectively, for a few years, variations
in metal accumulation among populations and their arbuscular mycorrhizal (AM) status have not been fully explored. Six populations
of P. vittata and four populations of S. alfredii from southeast China were investigated. Up to 1,373 As, 680 Pb, 376 Zn, 4.8 Cd, 169 Cu mg kg−1 in fronds of P. vittata and 358 As, 2,290 Pb, 23,403 Zn, 708 Cd, 342 Cu mg kg−1 in shoots of S. alfredii were detected. Constitutive properties of As and Zn hyperaccumulation in metallicolous populations of P. vittata and S. alfredii, respectively, were confirmed. However, Cd hyperaccumulation in S. alfredii varied among populations. The two hyperaccumulators varied in efficiency in taking up other heavy metals. Different metal
tolerance strategies adopted by the two hyperaccumulators varied among plant species and metal species. Low to moderate levels
of AM colonization in P. vittata (4.2–12.8%) and S. alfredii (8.5–45.8%) were observed at uncontaminated and metal-contaminated sites. The relationship between metal concentrations and
AM colonization in the two hyperacumulators was also examined. The abundance of AM fungal spores ranged from 16 to 190 spores
per 25 g soil. Glomus microaggregatum, Glomus mosseae, Glomus brohultii and Glomus geosporum were the most common species associated with both P. vittata and S. alfredii. To our knowledge, this is the first report of AM fungal status in rhizosphere of P. vittata and S. alfredii. 相似文献
989.
990.
Cardenas JC Carvajal J Ruiz A 《Plastic and reconstructive surgery》2007,120(6):1741-2; author reply 1743