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1.
The oxidative stress response in Bacillus subtilis 总被引:9,自引:0,他引:9
Barbara C.A. Dowds 《FEMS microbiology letters》1994,124(3):255-263
Abstract Bacillus subtilis undergoes a typical bacterial stress response when exposed to low concentrations (0.1 mM) of hydrogen peroxide. Protection is thereby induced against otherwise lethal, challenge concentrations (10 mM) of this oxidant and a number of proteins are induced including the scavenging enzymes, catalase and alkyl hydroperoxide reductase, and a putative DNA binding and protecting protein. Induced protection against higher concentrations (10–30 mM) of hydrogen peroxide is eliminated in a catalase-deficient mutant. Both RecA and Spo0A influence the basal but not the induced resistance to hydrogen peroxide. A regulatory mutation has been characterized that affects the inducible phenotype and is constitutively resistant to high concentrations of hydrogen peroxide. This mutant constitutively overexpresses the proteins induced by hydrogen peroxide in the wild-type. The resistance of spores to hydrogen peroxide is partly attributable to binding of small acid soluble proteins by the spore DNA and partly to a second step which coincides with the depletion of the NADH pool, which may inhibit the generation of hydroxyl radicals from hydrogen peroxide. 相似文献
2.
Summary Histochemical techniques applied at the ultrastructural level have established the periplasmic space as the site of cell bound alkaline phosphatase activity inAnabaena cylindrica andCoccochloris peniocytis. For localization of activity unfixed cells were reacted with calcium nitrate, which acts as the initial capture reagent. After this deposition, the cells were suspended in 2% lead nitrate to convert the calcium phosphate to more electron dense lead phosphate. The majority of cell bound activity appeared to be associated with layer 3 of the cell wall. InA. cylindrica a secondary site of cell bound activity appeared to be in the sheath. Placement in a phosphate free medium caused a substantial increase in the enzyme activity ofA. cylindrica while the activity present in log phase cells ofC. peniocytis was similar to that found in phosphate starved cells.C. peniocytis also secretes the enzyme into the surrounding medium. 相似文献
3.
Many polluted lakes in Europe are being restored and phosphorus concentrations have dropped dramatically in these lakes. We studied the genetic structure of Daphnia galeata over the past 30 years in Lake Greifensee, Switzerland, a period during which the phosphorus concentration in the lake reduced dramatically. Distinct genotypes of D. galeata were hatched from diapausing eggs extracted from six different time horizons in dated sediments. We compared juvenile growth, size and egg production of D. galeata reared on high-P and low-P algae to investigate whether Daphnia have evolved to grow better on phosphorus-limited algae. Our results indicate that life histories of D. galeata differed significantly between both food types. We also found significant clone effects for size and egg number. But we found no significant interaction between the depth from which the clones were selected and food quality. This means that we found no evidence for adaptive micro-evolution in response to P reduction in the lake. We discuss our results in relation to other studies that found evidence for adaptive micro-evolution in comparable time frames. 相似文献
4.
pp60
c-src
kinase activity can be increased by phosphotyrosine dephosphorylation or growth factor-dependent phosphorylation reactions. Expression of the transmembrane phosphotyrosine phosphatase (PTPase) CD45 has been shown to inhibit growth factor receptor signal transduction (Mooney, RA, Freund, GG, Way, BA and Bordwell, KL (1992) J Biol Chem 267, 23443–23446). Here it is shown that PTPase expression decreased platelet-derived growth factor (PDGF)-dependant activation of pp60
c-src
but failed to increase hormone independent (basal) pp60
c-src
activity. PDGF-dependent tyrosine phosphorylation of its receptor was reduced by approximately 60% in cells expressing the PTPase. In contrast, a change in phosphotyrosine content of pp60
c-src
was not detected in response to PDGF or in PTPase+cells. PDGF increased the intrinsic tyrosine kinase activity of pp60
c-src
in both control and PTPase+cells but the effect was smaller in PTPase+cells. In anin vitro assay, hormone-stimulate pp60
c-src
autophosphorylation from PTPase+ cells was decreased 64±22%, and substrate phosphorylation by pp60
c-src
was reduced 54±16% compared to controls. Hormone-independent pp60
c-src
kinase activity was unchanged by expression of the PTPase. pp60
c-src
was, however, anin vitro substrate for CD45, being dephosphorylated at both the regulatory (Tyr527) and kinase domain (Tyr416) residues. In addition,in vitro dephosphorylation by CD45 increased pp60
c-src
activity. These findings suggest that the PDGF receptor was anin vivo substrate of CD45 but pp60
c-src
was not. The lack of activation of pp60
c-src
in the presence of expressed PTPase may demonstrate the importance of compartmentalization and/or accessory proteins to PTPase-substrate interactions.Abbreviations PTPase
phosphotyrosine phosphatase
- PDGF
platelet-derived growth factor
- PMSF
phenylmethylsulfonyl fluoride
- LCA, CD45
leukocyte common antigen
- PBS
phosphate buffered saline
- SDS
sodium dodecyl sulfate
- PAGE
polyacrylamide gel electrophoresis
- DTT
dithiothreitol
- Na3VO4
sodium orthovanadate
- PV
pervanadate
- -ME
-mercaptoethanol 相似文献
5.
Structures of the O-linked oligosaccharides of a complex glycoconjugate from Pseudallescheria boydii
Nonreducing O-linked oligosaccharides were obtained from the peptidorhamnomannan of mycelia of Pseudallescheria boydii by alkaline beta-elimination under reducing conditions. They were separated by gel filtration chromatography to give three oligosaccharide fractions. The major oligosaccharide from fraction 1 was characterized by a combination of techniques including electrospray ionization quadrupole time-of-flight tandem mass spectrometry (ESI MS/MS), matrix-assisted laser desorption ionization mass spectrometry (MALDI MS), nuclear magnetic resonance (NMR), and methylation gas-liquid chromatography-mass spectrometry (GC-MS) analysis. It was branched, with a principal chain of alpha-Rhap-(1 --> 3)-alpha-Rhap-(1 --> 3)-alpha-Manp-(1 --> 2)-Man-ol substituted at O-6 of mannitol with an alpha-Glcp-(1 --> 4)-beta-Galp group. Species containing one and two additional alpha-Glcp-(1 --> 4) substituents in the rhamnose branch were also present. The major component of fraction 2 was a substructure of oligosaccharide-1, lacking a hexose from the Glc-Gal branch. Fraction 3 contained a mixture of smaller, unbranched, oligosaccharides. In hapten inhibition tests, fractions 1 and 2 blocked the reaction between peptidorhamnomannan (PRM) and rabbit anti-P. boydii mycelium hyperimmune serum by approximately 75%, whereas fraction 3 inhibited by approximately 55%. 相似文献
6.
Tobias Kreibich Reinhard Saborowski Wilhelm Hagen Barbara Niehoff 《Helgoland Marine Research》2008,62(3):241-249
Changes in fatty acid patterns, digestive and metabolic enzyme activities and egg production rates (EPR) were studied in the
small calanoid copepod Temora longicornis. Female copepods were collected in spring 2005 off Helgoland (North Sea). In the laboratory one group of copepods was fed
with the cryptophycean Rhodomonas baltica for a period of 3 days. Another group of copepods was maintained without food. According to the fatty acid patterns, animals
from the field were feeding on a more detrital, animal-based and to a minor extent to a diatom-based diet. Under laboratory
conditions, females rapidly accumulated fatty acids such as 18:4 (n-3), 18:3 (n-3) and 18:2 (n-6) which are specific of R. baltica. Diatom-specific fatty acids such as 16:1 (n-7) were strongly reduced. In fed animals the activities of digestive and metabolic
enzymes remained constant and egg production rates were highest on day 2. Starving animals, in contrast, showed significantly
reduced faecal pellet production and EPR. Proteolytic enzyme activity decreased rapidly within 24 h and remained at a low
level until the end of the experiment. Citrate synthase decreased continuously as well. T. longicornis rapidly reacts to dietary changes and food depletion. It has limited energy stores and, thus, strongly depends on continuous
food supply. 相似文献
7.
Barbara Claas Jeffrey Dean 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2006,192(10):1021-1036
Separately delivered visual and lateral line stimuli elicit similar but not identical orientation and approach by intact, sighted Xenopus. Response frequencies for visual stimuli declined sharply for distant or caudal stimuli while those for lateral line stimuli changed little. Turn angles correlated highly with stimulus angles but were smaller on average, so regression slopes were less than one. Regression slopes were smaller for visual than for lateral line stimuli, but this apparent difference was due to different distributions of stimulus distance interacting with the toad’s rotation center. Errors in final headings, most often under-rotations, did not differ by modality. Frequencies of lunges and arm capture movements were higher for visual stimuli both overall and especially for rostral proximal stimuli. The results demonstrate accurate orientation by sighted Xenopus to visual and lateral line stimuli; they are consistent with expectations based on in-register tectal maps. Orientation to lateral line stimuli is similar to previous results with blinded animals, revealing no heightened acuity in the latter. Modality differences indicate that the lateral line system is better for omnidirectional orientation and approach to distant stimuli whereas the visual system is more attuned to nearby rostral stimuli and more apt to mediate strikes.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at . 相似文献
8.
Barbara Kroczynska Rengang Zhou Clifford Wood Jan A. Miernyk 《Plant molecular biology》1996,31(3):619-629
The nucleotide sequence of a cDNA clone fromArabidopsis thaliana ecotype Columbia was determined, and the corresponding amino sequence deduced. The open reading frame encodes a protein, AtJ1, of 368 residues with a molecular mass of 41 471 Da and an isoelectric point of 9.2. The predicted sequence contains regions homologous to the J- and cysteine-rich domains ofEscherichia coli DnaJ, but the glycine/phenylalanine-rich region is not present. Based upon Southern analysis,Arabidopsis appears to have a singleatJ1 structural gene. A single species of mRNA, of 1.5 kb, was detected whenArabidopsis poly(A)+ RNA was hybridized with theatJ1 cDNA. The function ofatJ1 was tested by complementation of adnaJ deletion mutant ofE. coli, allowing growth in minimal medium at 44°C. The AtJ1 protein was expressed inE. coli as a fusion with the maltose binding protein. This fusion protein was purified by amylose affinity chromatography, then cleaved by digestion with the activated factor X protease. The recombinant AtJ1 protein was purified to electrophoretic homogeneity.In vitro, recombinant AtJ1 stimulated the ATPase activity of bothE. coli DnaK and maize endosperm cytoplasmic Stress70. The deduced amino acid sequence of AtJ1 contains a potential mitochondrial targeting sequence at the N-terminus. Radioactive recombinant AtJ1 was synthesized inE. coli and purified. When the labeled protein was incubated with intact pea cotyledon mitochondria, it was imported and proteolytically processed in a reaction that depended upon an energized mitochondrial membrane.Abbreviations MBP
maltose binding protein
- PCR
polymerase chain reaction
- Stress70c
the cytosolic member of the 70 kDA family of stress-related proteins 相似文献
9.
Berent-Spillson A Robinson AM Golovoy D Slusher B Rojas C Russell JW 《Journal of neurochemistry》2004,89(1):90-99
Glutamate carboxypeptidase II (GCP II) inhibition has previously been shown to be protective against long-term neuropathy in diabetic animals. In the current study, we have determined that the GCP II inhibitor 2-(phosphonomethyl) pentanedioic acid (2-PMPA) is protective against glucose-induced programmed cell death (PCD) and neurite degeneration in dorsal root ganglion (DRG) neurons in a cell culture model of diabetic neuropathy. In this model, inhibition of caspase activation is mediated through the group II metabotropic glutamate receptor, mGluR3. 2-PMPA neuroprotection is completely reversed by the mGluR3 antagonist (S)-alpha-ethylglutamic acid (EGLU). In contrast, group I and III mGluR inhibitors have no effect on 2-PMPA neuroprotection. Furthermore, we show that two mGluR3 agonists, the direct agonist (2R,4R)-4-aminopyrrolidine-2, 4-dicarboxylate (APDC) and N-acetyl-aspartyl-glutamate (NAAG) provide protection to neurons exposed to high glucose conditions, consistent with the concept that 2-PMPA neuroprotection is mediated by increased NAAG activity. Inhibition of GCP II or mGluR3 may represent a novel mechanism to treat neuronal degeneration under high-glucose conditions. 相似文献
10.