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181.
Morán-Barrio J González JM Lisa MN Costello AL Peraro MD Carloni P Bennett B Tierney DL Limansky AS Viale AM Vila AJ 《The Journal of biological chemistry》2007,282(25):18286-18293
Metallo-beta-lactamases (MbetaLs) are zinc-dependent enzymes able to hydrolyze and inactivate most beta-lactam antibiotics. The large diversity of active site structures and metal content among MbetaLs from different sources has limited the design of a pan-MbetaL inhibitor. Here we report the biochemical and biophysical characterization of a novel MbetaL, GOB-18, from a clinical isolate of a Gram-negative opportunistic pathogen, Elizabethkingia meningoseptica. Different spectroscopic techniques, three-dimensional modeling, and mutagenesis experiments, reveal that the Zn(II) ion is bound to Asp120, His121, His263, and a solvent molecule, i.e. in the canonical Zn2 site of dinuclear MbetaLs. Contrasting all other related MbetaLs, GOB-18 is fully active against a broad range of beta-lactam substrates using a single Zn(II) ion in this site. These data further enlarge the structural diversity of MbetaLs. 相似文献
182.
Rostyslav R. Panchuk Natalia M. Boiko Maxim D. Lootsik Rostyslav S. Stoika 《Central European Journal of Biology》2007,2(1):71-86
The main goal of this study was to evaluate if specific cytokine expression in the NK/Ly lymphoma cells might be involved
in development of intoxication in the tumor-bearing animals. RT-PCR analysis was used to study an expression of mRNA coding
for IL-1α, IL-6, TNF-α, TNF-β and VEGF. ELISA was used to evaluate IL-6 and IFN-γ concentration in the ascitic fluid. Cytomorphological investigation of tumor cells was done after standard Romanovsky-Giemsa
staining, and chromatin staining was performed with hematoxyline and neutral red. Lactate dehydrogenase and acid phosphatase
release from tumor cells was estimated. It was revealed that the level of mRNA coding for VEGF and IL-6 was significant in
the lymphoma cells. The level of VEGF mRNA was initially high and did not change during tumor progression, while the level
of expression of IL6 mRNA was low at the initial stages of tumor growth and markedly increased (up to 5-fold) at the terminal
stages. The obtained data on IL-6 mRNA expression were confirmed by ELISA, which showed more than 6-fold increase (from 90
to 570 pg/ml) in the IL-6 concentration in the ascitic fluid at late stages of NK/Ly tumor development. On the contrary to
IL-6, concentration of IFN-γ in the ascitic fluid was very high at early stages of tumor development (1,000 pg/ml) and it markedly decreased (up to 30-fold,
30 pg/ml) at the terminal stages of tumor development. The high levels of IL-6 mRNA in tumor cells and IL-6 content in extracellular
medium correlated with cell deterioration, as revealed by cytomorphologic study and the release of intracellular enzymes into
extracellular medium. We suggest that an enhanced production and release of IL-6 by lymphoma cells can cause intoxication
and exhaustion of the organism observed at terminal stages of tumor growth. 相似文献
183.
184.
Acid-sensing ion channels (ASIC) are ligand-gated cation channels that are highly expressed in peripheral sensory and central neurons. ASIC are transiently activated by decreases in extracellular pH and are thought to play important roles in sensory perception, neuronal transmission, and excitability, and in the pathology of neurological conditions, such as brain ischemia. We demonstrate here that the heavy metals Ni(2+) and Cd(2+) dose-dependently inhibit ASIC currents in hippocampus CA1 neurons and in Chinese hamster ovary (CHO) cells heterologously expressing these channels. The effects of both Ni(2+) and Cd(2+) were voltage-independent, fast, and reversible. Neither metal affected activation and desensitization kinetics but rather decreased pH-sensitivity. Moreover, distinct ASIC isoforms were differentially inhibited by Ni(2+) and Cd(2+). External application of 1 mM Ni(2+) rapidly inhibited homomeric ASIC1a and heteromeric ASIC1a/2a channels without affecting ASIC1b, 2a, and ASIC3 homomeric channels and ASIC1a/3 and 2a/3 heteromeric channels. In contrast, external Cd(+) (1 mM) inhibited ASIC2a and ASIC3 homomeric channels and ASIC1a/2a, 1a/3, and 2a/3 heteromeric channels but not ASIC1a homomeric channels. The acid-sensing current in isolated rat hippocampus CA1 neurons, thought to be carried primarily by ASIC1a and 1a/2a, was inhibited by 1 mM Ni(2+). The current study identifies ASIC as a novel target for the neurotoxic heavy metals Cd(2+) and Ni(2+). 相似文献
185.
shRNA knockdown of Bmi-1 reveals a critical role for p21-Rb pathway in NSC self-renewal during development 总被引:7,自引:0,他引:7
Knockout studies have shown that the polycomb gene Bmi-1 is important for postnatal, but not embryonic, neural stem cell (NSC) self-renewal and have identified the cell-cycle inhibitors p16/p19 as molecular targets. Here, using lentiviral-delivered shRNAs in vitro and in vivo, we determined that Bmi-1 is also important for NSC self-renewal in the embryo. We found that neural progenitors depend increasingly on Bmi-1 for proliferation as development proceeds from embryonic through adult stages. Acute shRNA-mediated Bmi-1 reduction causes defects in embryonic and adult NSC proliferation and self-renewal that, unexpectedly, are mediated by a different cell-cycle inhibitor, p21. Gene array analyses revealed developmental differences in Bmi-1-controlled expression of genes in the p21-Rb cell cycle regulatory pathway. Our data therefore implicate p21 as an important Bmi-1 target in NSCs, potentially with stage-related differences. Understanding stage-related mechanisms underlying NSC self-renewal has important implications for development of stem cell-based therapies. 相似文献
186.
Biodeterioration of crude oil and oil derived products: a review 总被引:2,自引:0,他引:2
Natalia A. Yemashova Valentina P. Murygina Dmitry V. Zhukov Arpenik A. Zakharyantz Marina A. Gladchenko Vasu Appanna Sergey V. Kalyuzhnyi 《Reviews in Environmental Science and Biotechnology》2007,6(4):315-337
Biodeterioration of crude oil and oil fuels is a serious economic and an environmental problem all over the world. It is impossible
to prevent penetration of microorganisms in oil and fuels both stored in tanks or in oilfields after drilling. Both aerobic
and anaerobic microorganisms tend to colonise oil pipelines and oil and fuel storage installations. Complex microbial communities
consisting of both hydrocarbon oxidizing microorganisms and bacteria using the metabolites of the former form an ecological
niche where they thrive. The accumulation of water at the bottom of storage tanks and in oil pipelines is a primary prerequisite
for development of microorganisms in fuels and oil and their subsequent biological fouling. Ability of microorganisms to grow
both in a water phase and on inter-phase of water/hydrocarbon as well as the generation of products of their metabolism worsen
the physical and chemical properties of oils and fuels. This activity also increases the amount of suspended solids, leads
to the formation of slimes and creates a variety of operational problems. Nowadays various test-systems are utilized for microbial
monitoring in crude oils and fuels; thus allowing an express determination of both the species and the quantities of microorganisms
present. To suppress microbial growth in oils and fuels, both physico-mechanical and chemical methods are applied. Among chemical
methods, the preference is given to substances such as biocides, additives, the anti-freezing agents etc that do not deteriorate
the quality of oil and fuels and are environmentally friendly. This review is devoted to the analysis of the present knowledge
in the field of microbial fouling of crude oils and oil products. The methods utilized for monitoring of microbial contamination
and prevention of their undesirable activities are also evaluated. The special focus is given to Russian scientific literature
devoted to crude oil and oil products biodeterioration. 相似文献
187.
Margison GP Butt A Pearson SJ Wharton S Watson AJ Marriott A Caetano CM Hollins JJ Rukazenkova N Begum G Santibáñez-Koref MF 《DNA Repair》2007,6(8):1222-1228
Recent in silico analysis has revealed the presence of a group of proteins in pro and lower eukaryotes, but not in Man, that show extensive amino acid sequence similarity to known O(6)-alkylguanine-DNA alkyltransferases, but where the cysteine at the putative active site is replaced by another residue, usually tryptophan. Here we review recent work on these proteins, which we designate as alkyltransferase-like (ATL) proteins, and consider their mechanism of action and role in protecting the host organisms against the biological effects of O(6)-alkylating agents, and their evolution. ATL proteins from Escherichia coli (eAtl, transcribed from the ybaz open reading frame) and Schizosaccharomyces pombe (Atl1) are able to bind to a range of O(6)-alkylguanine residues in DNA and to reversibly inhibit the action of the human alkyltransferase (MGMT) upon these substrates. Isolated proteins were not able to remove the methyl group in O(6)-methylguanine-containing DNA or oligonucleotides, neither did they display glycosylase or endonuclease activity. S. pombe does not contain a functional alkyltransferase and atl1 inactivation sensitises this organism to a variety of alkylating agents, suggesting that Atl1 acts by binding to O(6)-alkylguanine lesions and signalling them for processing by other DNA repair pathways. Currently we cannot exclude the possibility that ATL proteins arose through independent mutation of the alkyltransferase gene in different organisms. However, analyses of the proteins from E. coli and S. pombe, are consistent with a common function. 相似文献
188.
The function of terpene natural products in the natural world 总被引:5,自引:0,他引:5
As the largest class of natural products, terpenes have a variety of roles in mediating antagonistic and beneficial interactions among organisms. They defend many species of plants, animals and microorganisms against predators, pathogens and competitors, and they are involved in conveying messages to conspecifics and mutualists regarding the presence of food, mates and enemies. Despite the diversity of terpenes known, it is striking how phylogenetically distant organisms have come to use similar structures for common purposes. New natural roles undoubtedly remain to be discovered for this large class of compounds, given that such a small percentage of terpenes has been investigated so far. 相似文献
189.
This article summarizes the current understanding of known variant forms of the MGMT gene that encode an altered protein. Epidemiological studies have been carried out to test whether these alterations are associated with altered cancer risk. Laboratory studies using recombinant proteins and cells expressing the known variants have investigated the possible effects of these sequence alterations on the ability of the encoded O(6)-alkylguanine-DNA alkyltransferase protein to protect cells from alkylation damage and to respond to therapeutic inactivators currently undergoing trials for cancer chemotherapy. 相似文献
190.