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891.
By using an oligonucleotide mixture corresponding to a region highly conserved among alternative sigma factors we identified
a new σ factor gene (rpoH) from Rhodobacter capsulatus. This gene encodes a protein of 34 kDa with strong similarity to the RpoH (σ
32) factors from other bacterial species. It was not possible to inactivate the R. capsulatusrpoH gene by introducing a resistance cassette, implying that it is essential for growth. The 5′ ends of the mRNAs were mapped
to two sequences with similarity to an rpoH- and an rpoD-dependent promoter, respectively. The amounts of both these mRNAs increased after heat shock, but were unaffected by a decrease
in oxygen tension. Western analysis using a σ factor-specific antibody revealed the accumulation of a protein of about 34 kDa after heat shock, and an increase in the
amounts of a protein with the same size after reduction of oxygen tension in R. capsulatus cultures.
Received: 16 March 1998 / Accepted: 28 July 1998 相似文献
892.
Structural-Thermodynamic Relationships of Interactions in the N-Terminal ATP-Binding Domain of Hsp90
Sanjay Nilapwar Eleanor Williams Christosmos Prodromou Mark A. Williams 《Journal of molecular biology》2009,392(4):923-9317
Despite its importance as a target in anti-cancer therapeutics and the numerous rational-based inhibitor design efforts aimed at it, there are only limited data available on structural-thermodynamic relationships of interactions of the N-terminal ATP-binding domain of Hsp90 (N-Hsp90). Here, we redress this by presenting an investigation of binding of nucleotides and ansamycin compounds to this domain. Interactions of nucleotides with N-Hsp90 are relatively weak (> 10 μM) and are strongly enthalpy driven over the temperature range 10-25 °C. Geldanamycin (GA) and its analogues 17-AAG [17-(allylamino)-17-demethoxy-GA] and 17-DMAG (17-N,N-dimethylaminoethylamino-17-demethoxy-GA) bind more strongly and have a dominant favourable enthalpic contribution over the temperature range investigated. We investigated the temperature dependence of the enthalpic contribution to binding. We found that while the ansamycin compounds have the commonly observed negative value, the nucleotides show a negligible or even a positive ΔCp of binding. These data represent the first observation of a single binding site for which interactions with different ligands result in both negative and positive ΔCp values. By addressing the likely impact of the potential contributions from protein-ligand interactions, we are able to attribute the anomalous ΔCp for the nucleotides largely to a change in the conformation of the domain structure and local motion in the lid region of N-Hsp90 with the concomitant exposure of hydrophobic amino acid side chains. 相似文献
893.
Multitargeting involves the application of molecules that are deliberately intended to bind to two or more unrelated cellular targets with high affinity. In epigenetic chemical biology and drug discovery, the rational design of multitargeting agents has evolved to a sophisticated level, and there are now five examples that have reached clinical trials. This review covers recent developments in the field and future prospects. 相似文献
894.
Ribonuclease (EC 2.7.7.17) activity in the obligate halophyte Suaeda maritima (L.) Dum. var. macrocarpa Moq. was studied in relation to salinity (increasing concentrations of NaCl) of incubation and growth media. In vitro, the addition of 50 to 400 m M NaCl did not affect ribonuclease activity. This result, which was also found for Phaseolus vulgaris , indicates that the hydrolase is insensitive to high saline concentrations. The subcellular distribution of RNase activity did not change significantly with the salinity of the medium or with the age of the plant. The microsomal ribonuclease activity expressed on a fresh weight basis represented in every case less than 6% of the total activity. After 23 days of culture, the absence of salt stimulated the activity of soluble ribonuclease in aerial parts of Suaeda ; inversely, the capacity of the enzyme was lower under optimal saline conditions (130 m M NaCl). This was also evidenced by transfer of whole plants from a non-saline to a saline medium. Such a saline shock caused a decrease followed by a stabilization of the capacity of ribonuclease from Suaeda . The influx of NaCl in the tissues lowered the activity of the hydrolase. 相似文献
895.
《Bioscience, biotechnology, and biochemistry》2013,77(11):2482-2485
We examined whether starvation affected the amount of EF-2 protein as well as the level of its mRNA in the liver and skeletal muscle of mice, to understand the molecular mechanism for nutritional adaptation of protein-turnover. Although the amount of EF-2 was diminished by starvation in each of the tissues examined, the amount of EF-2 mRNA did not decrease in parallel with the protein. 相似文献
896.
Abstract The amounts of mRNA and protein of plasma membrane proton-ATPase were measured in the salt-tolerant yeast Zygosaccharomyces rouxii by Northern and Western blot analyses. Although their amounts were independent of growth phase, their synthesis were induced when yeast cells were grown in the presence of NaCl or were subjected to NaCl shock. This finding was consistent with our previous result that plasma membrane proton-ATPase activity was elevated in Z. rouxii cells grown in medium containing high concentrations of NaCl. 相似文献
897.
Marta Menga Rosa Trotta Rosella Scrima Consiglia Pacelli Veronica Silvestri Claudia Piccoli Nazzareno Capitanio Arcangelo Liso 《生物化学与生物物理学报:疾病的分子基础》2018,1864(3):685-699
Fever-like hyperthermia is known to stimulate innate and adaptive immune responses. Hyperthermia-induced immune stimulation is also accompanied with, and likely conditioned by, changes in the cell metabolism and, in particular, mitochondrial metabolism is now recognized to play a pivotal role in this context, both as energy supplier and as signaling platform. In this study we asked if challenging human monocyte-derived dendritic cells with a relatively short-time thermal shock in the fever-range, typically observed in humans, caused alterations in the mitochondrial oxidative metabolism. We found that following hyperthermic stress (3 h exposure at 39 °C) TNF-α-releasing dendritic cells undergo rewiring of the oxidative metabolism hallmarked by decrease of the mitochondrial respiratory activity and of the oxidative phosphorylation and increase of lactate production. Moreover, enhanced production of reactive oxygen and nitrogen species and accumulation of mitochondrial Ca2+ was consistently observed in hyperthermia-conditioned dendritic cells and exhibited a reciprocal interplay. The hyperthermia-induced impairment of the mitochondrial respiratory activity was (i) irreversible following re-conditioning of cells to normothermia, (ii) mimicked by exposing normothermic cells to the conditioned medium of the hyperthermia-challenged cells, (iii) largely prevented by antioxidant and inhibitors of the nitric oxide synthase and of the mitochondrial calcium porter, which also inhibited release of TNF-α. These observations combined with gene expression analysis support a model based on a thermally induced autocrine signaling, which rewires and sets a metabolism checkpoint linked to immune activation of dendritic cells. 相似文献
898.
Liquid-liquid phase separation of RBGD2/4 is required for heat stress resistance in Arabidopsis 总被引:1,自引:0,他引:1
《Developmental cell》2022,57(5):583-597.e6
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899.
P. G. Petronini A. E. Caccamo R. R. Alfieri M. A. Bonelli A. F. Borghetti 《Amino acids》2001,20(4):363-380
Summary. In 3T3 cells temperatures higher than physiological stimulated amino acid transport activity in a dose-dependent manner up
to 44°C. However, the temperature increase did not induce widespread transport increase of all other nutrients tested. The
activities of both amino acid transport systems A and ASC were enhanced within a few minutes following cell exposure to increased
temperature. The maintenance of this effect required continuous exposure of the cells to hyperthermia. Kinetic analysis indicated
that the stimulation of the activity of transport System A occurred through a mechanism affecting Vmax rather than Km. The
continuous presence of cycloheximide did not prevent the transport changes induced by hyperthermia. These results suggest
that the increased amino acid uptake reflects an activation or relocation of existing amino acid transport proteins. During
the hyperthermic treatment, the content of ninhydrin-positive substances (NPS), mostly amino acids, increased within the cells
and the accumulation of these compatible osmolytes was parallelled by an increase in cell volume. The withdrawal of amino
acids from the culture medium immediately before and during the shock phase counteracted the increase and reduced the NPS
content but did not prevent the increase in amino acid transport, the cell swelling and the induction of the heat shock response.
Received June 30, 1999 Accepted July 27, 2000 相似文献
900.