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11.
Spa32 regulates a switch in substrate specificity of the type III secreton of Shigella flexneri from needle components to Ipa proteins 下载免费PDF全文
Magdalena J Hachani A Chamekh M Jouihri N Gounon P Blocker A Allaoui A 《Journal of bacteriology》2002,184(13):3433-3441
Type III secretion systems (TTSS) are essential virulence determinants of many gram-negative bacteria and serve, upon physical contact with target cells, to translocate bacterial proteins directly across eukaryotic cell membranes. The Shigella TTSS is encoded by the mxi/spa loci located on its virulence plasmid. By electron microscopy secretons are visualized as tripartite with an external needle, a transmembrane domain, and a cytoplasmic bulb. In the present study, we generated a Shigella spa32 mutant and studied its phenotype. The spa32 gene shows low sequence homology to Salmonella TTSS1 invJ/spaN and to flagellar fliK. The spa32 mutant, like the wild-type strain, secreted the Ipas and IpgD, which are normally secreted via the TTSS, at low levels into the growth medium. However, unlike the wild-type strain, the spa32 mutant could neither be induced to secrete the Ipas and IpgD instantaneously upon addition of Congo red nor penetrate HeLa cells in vitro. Additionally, the Spa32 protein is secreted in large amounts by the TTSS during exponential growth but not upon Congo red induction. Interestingly, electron microscopy analysis of the spa32 mutant revealed that the needle of its secretons were up to 10 times longer than those of the wild type. In addition, in the absence of induction, the spa32 mutant secreted normal levels of MxiI but a large excess of MxiH. Taken together, our data indicate that the spa32 mutant presents a novel phenotype and that the primary defect of the mutant may be its inability to regulate or control secretion of MxiH. 相似文献
12.
Brakch N Lazar N Panchal M Allemandou F Boileau G Cohen P Rholam M 《Biochemistry》2002,41(5):1630-1639
Proline residues, known to have special structural properties, induce particular conformations which participate in some biological functions. Two prolines (Pro(-9), Pro(-5)) located near the processing sites (Arg(-15) and Arg(-2)Lys(-)(1)) of human prosomatostatin were previously shown to be important for cleavage of the precursor into somatostatin-28 (S-28) and somatostatin-14 (S-14) [Gomez et al. (1989) EMBO J. 8, 2911-2916]. In this study, the importance of the pentapeptide P-A-M-A-P sequence (P-(X)(3)-P pattern), located in the S-28(1-12) segment connecting the mono- and dibasic cleavage sites, was investigated by using site-directed mutagenesis. Analysis of prosomatostatin-derived peptides produced by expression of mutated cDNA species in Neuro2A cells indicated that (i) deletion of PAMAP decreased S-14 production, (ii) deletion of the two Pro residues almost abolished the cleavage at the dibasic site, and (iii) Pro displacement generating the AMAPP motif resulted in a decrease of S-28 production. Moreover, both theoretical and spectroscopic studies of synthetic peptides reproducing the S-28(1-12) sequence bearing critical mutations showed that this sequence can organize as an alpha helical structure. These observations demonstrate that NPAMAP constitutes an accurate alpha-helix nucleation motif allowing for the generation of equal amounts of S-28 and S-14 from their common precursor in Neuro2A cells. Moreover, they emphasize the importance of the S-28(1-12) segment joining Arg(-15) and Arg(-2)Lys(-1) cleavage sites whose conformational organization is essential for controlling their accessibility to the appropriate processing proteases. 相似文献
13.
Berrada W Naya A Ouafik L Bourhim N 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》2000,125(4):117-449
Tissue distribution of the cytosolic and mitochondrial glycerol-3-phosphate dehydrogenase (cGPDH and mGPDH) activities in jerboa (Jaculus orientalis), a hibernator, shows the highest level of enzyme activity in skeletal muscle and brown adipose tissue, respectively. The effect of hibernation on cGPDH indicates an increase of activity in all tissues examined. In contrast, hibernation decreases mGPDH activity in all tissues, except skeletal muscle. The effect of thyroid hormones on GPDH activity was tissue specific: in kidneys, cGPDH activity doubled in euthermic jerboas treated with T4. In contrast, 6-n-propyl-2-thiouracil treatment provokes an increase of enzyme activity in brown adipose tissue, liver and brain. T4 treatment leads to a 2.7-fold increase in liver mGPDH activity. 6-n-propyl-2-thiouracil treatment decreases mGPDH activity in the skeletal muscle whereas the opposite effect was observed in brain. Dexamethasone stimulates cGPDH in all tissues examined, except skeletal muscle and kidneys. In the case of mGPDH activity, this increase was observed only for brown adipose tissue and brain. Our results suggest that hibernation, thyroid hormones and dexamethasone probably play a role in the regulation of cGPDH and mGPDH activities in jerboa. Our findings confirm that these enzymes are involved in metabolic adaptation to thermal stress in Jaculus orientalis. 相似文献
14.
Maria Virgínia Alves Martins Noureddine Zaaboub Lotfi Aleya Fabrizio Frontalini Egberto Pereira Paulo Miranda Miguel Mane Fernando Rocha Lazaro Laut Monia El Bour 《PloS one》2015,10(9)
This study investigated the environmental quality of the Bizerte Lagoon (Tunisia) through an integrated approach that combined environmental, biogeochemical, and living benthic foraminiferal analyses. Specifically, we analyzed the physicochemical parameters of the water and sediment. The textural, mineralogical, and geochemical characteristics of the sediment, including total organic carbon, total nitrogen, simultaneously extracted metals (SEM), acid volatile sulfides (AVS), chlorophyll a, CaCO3, and changes in bacterial populations and carbon isotopes were measured. The SEM/AVS values indicated the presence of relatively high concentrations of toxic metals in only some areas. Foraminiferal assemblages were dominated by species such as A. parkinsoniana (20–91%), Bolivina striatula (<40%), Hopkinsina atlantica (<17%), and Bolivina ordinaria (<15%) that cannot be considered typical of impacted coastal lagoons both in Mediterranean and northeast Atlantic regions. The results of this work suggest that Bizerte Lagoon is a unique setting. This lagoon is populated by typical marine species that invaded this ecosystem, attracted not only by the prevailing favorable environmental conditions but also by the abundance and quality of food. The results indicate that the metal pollution found in some areas have a negative impact on the assemblages of foraminifera. At present, however, this negative impact is not highly alarming. 相似文献
15.
Atika Meklat Noureddine Bouras Amar Riba Abdelghani Zitouni Florence Mathieu Manfred Rohde Peter Schumann Cathrin Spröer Hans-Peter Klenk Nasserdine Sabaou 《Antonie van Leeuwenhoek》2014,106(2):287-292
A halophilic actinomycete strain, designated H27T, was isolated from a soil sample collected from a hypersaline habitat in Djelfa Province (North-Central Algeria), and then investigated using a polyphasic taxonomic approach. The strain was observed to produce poor aerial mycelium, which formed short chains of oval to cylindrical-shaped spores at maturity, and non fragmented substrate mycelium. The optimum NaCl concentration for growth was found to be 10–15 % (w/v) and the optimum growth temperature and pH were found to be 28–37 °C and 6–7, respectively. The diagnostic diamino acid in the cell-wall peptidoglycan was identified as meso-diaminopimelic acid. The predominant menaquinones of strain H27T were identified as MK-11 (H4) and MK-10 (H6). The major fatty acids were found to be iso-C16:0, anteiso-C17:0, 10 methyl C17:0 and 10 methyl C16:0. The diagnostic phospholipids detected were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine and phosphatidylinositol. The chemotaxonomic properties of strain H27T are consistent with those shared by members of the genus Streptomonospora. 16S rRNA gene sequence analysis indicated that strain H27T is most closely related to Streptomonospora alba DSM 44588T (98.8 %) and Streptomonospora flavalba DSM 45155T (98.7 %) whereas the DNA–DNA relatedness values between strain H27T and the two type strains were 17.1 and 57.9 %, respectively. Based on the combined genotypic and phenotypic evidence, it is proposed that strain H27T should be classified as representative of a novel species, for which the name Streptomonospora algeriensis sp. nov. is proposed. The type strain is H27T (=DSM 45604T =CCUG 63369T =MTCC 11563T). 相似文献
16.
Rafika Saker Noureddine Bouras Abdelghani Zitouni Mostefa Ghoul Manfred Rohde Peter Schumann Cathrin Spröer Nasserdine Sabaou Hans-Peter Klenk 《Antonie van Leeuwenhoek》2014,106(5):1021-1030
Three halophilic mycelium-forming actinobacteria, strains H195T, H150 and H151, were isolated from a Saharan soil sample collected from Béni-isguen in the Mzab region (Ghardaïa, South of Algeria) and subjected to a polyphasic taxonomic characterisation. These strains were observed to show an aerial mycelium differentiated into coccoid spore chains and fragmented substrate mycelium. Comparative analysis of the 16S rRNA gene sequences revealed that the highest sequence similarities were to Saccharopolyspora qijiaojingensis YIM 91168T (92.02 % to H195T). Phylogenetic analyses showed that the strains H195T, H150 and H151 represent a distinct phylogenetic lineage. The cell-wall hydrolysate was found to contain meso-diaminopimelic acid, and the diagnostic whole-cell sugars were identified as arabinose and galactose. The major cellular fatty acids were identified as iso-C15:0, iso-C16:0, iso-C17:0 and anteiso-C17:0. The diagnostic phospholipid detected was phosphatidylcholine and MK-9 (H4) was found to be the predominant menaquinone. The genomic DNA G+C content of strain H195T was 68.2 mol%. On the basis of its phenotypic features and phylogenetic position, we propose that strain H195T represents a novel genus and species, Mzabimyces algeriensis gen. nov., sp. nov., within a new family, Mzabimycetaceae fam. nov. The type strain of M. algeriensis is strain H195T (=DSM 46680T = MTCC 12101T). 相似文献
17.
Elham Hassen Ghandri Nahla Noureddine Bouaouina Lotfi Chouchane 《Molecular biology reports》2010,37(1):119-126
Nasopharyngeal carcinoma (NPC) is a virally associated cancer which is highly prevalent in Southeast Asia and North Africa.
Several linkage analysis studies suggested the association of susceptibility HLA (Human Leukocyte Antigen) alleles and haplotypes
with NPC development. The HLA system is very polymorphic and according to the ethnic group studied, it has been found to have
the capacity to confer susceptibility or resistance to NPC. Our aim was to review the most important described genetic associations
of HLA class I in NPC and to comment on the inconsistent associations found in the different NPC incidence areas. We believe
that the mechanisms of these associations may involve HLA genes through the differential capacity of each allele to present
antigens. However, because HLA genes contain various linked candidate genes, HLA-NPC associations should be carefully interpreted. 相似文献
18.
Samia Dabbou Imed Rjiba Adel Echbili Noureddine Gazzah Beligh Mechri Mohamed Hammami 《化学与生物多样性》2010,7(7):1801-1813
Our study reports the triglyceride (triacylglycerol, TAG) composition of five new Tunisian virgin olive oil cultivars obtained through controlled crossings of the cultivar (cv.) Chemlali Sfax. These cultivars have been selected among a progeny of 500 olive descendants, based on an evaluation of the fatty‐acid (FA) composition of their oils. Among these samples, two were derived from the crossing with the cv. Sigoise as pollinator (SM634) or pollen acceptor (SM1110) and the others from the crossing with the cv. Meski as pollen acceptor (SM513, SM514, and SM517). The five descendants were characterized by a good fat value, a balanced FA composition, and a high content of triolein, varying between 26.9 (SM514) and 45.46% (SM1110). They had an improved FA composition as compared to that of the cv. Chemlali Sfax and their fruits were slightly bigger. The principal component analysis suggested that the TAG variables were more suitable than the total FAs for an optimum classification of the cultivar samples analyzed. The cultivars obtained through the crossing with the cv. Sigoise (as pollen acceptor or pollinator) had a more favorable composition of FAs and TAG than those obtained through the crossing with the cv. Meski, which indicated that genetic factors had the most important influence on the quality of the virgin olive oils. 相似文献
19.
Besma Sghaier-Hammami Jesús V. Jorrín-Novo Radhia Gargouri-Bouzid Noureddine Drira 《Phytochemistry》2010,71(11-12):1223-1236
Various supplements (abscisic acid (ABA) or sucrose) were added to the initial embryo culture medium (M3) with the aim of improving the vigour of vitroplants deriving from date palm somatic embryogenesis. ABA (20 and 40 μM) and sucrose (90 g/l) applied for 4 and 2 weeks respectively increased embryo thickness, with no apparent difference in length. ABA (5–40 μM) increased embryo proliferation rate. Somatic embryos maintained in modified M3 (M3 supplemented with ABA and an increased sucrose concentration) contained a higher amount of protein than those maintained in initial M3 (no ABA, 30 g/l of sucrose), with a 1.5–1.7-fold increase depending on the compound and concentration assayed. The 1-D and 2-DE protein profiles showed qualitative and quantitative differences between the somatic embryos cultured in initial M3 (control) and in modified M3. Statistical analysis of spot intensity was performed by principal component analysis, yielding two accurate groups of samples and determining the most discriminating spots. Samples were also clustered using Euclidean distance with an average linkage algorithm. Thirty-four variable spots were identified using mass spectrometry analysis. Identified proteins were classified into the following functional categories: energy metabolism (five proteins); protein translation, folding and degradation (9); redox maintenance (5); cytoskeleton (3); storage protein (2); and with no assigned function as (10). While “up-regulation” of stress-related proteins and “down-regulation” of energy metabolism proteins were observed in somatic embryos matured in M3 supplemented with ABA, storage proteins (legumin) were “up-regulated” in somatic embryos matured in M3 supplemented with increased sucrose. 相似文献
20.
Driss Mountassif Mostafa Kabine Rachid Manar Noureddine Bourhim Zaina Zaroual Norbert Latruffe MHammed Saïd El Kebbaj 《Ecological Indicators》2007,7(4):882-894
The individual cytotoxicity of cadmium chloride, iron sulphate and chromium nitrate has been investigated by using the freshwater ciliate Tetrahymena pyriformis. The metabolic enzymes and antioxidant defense biomarkers were assessed. The results obtained reveal that their metal salts have perturbed the physiology and morphology of T. pyriformis. Also, the biomarkers assessed were sensitive to the presence of metal salts and this sensitivity was metal salt and dose dependant. To estimate the impact of their metal salts on mitochondria, we studied their effects in vivo and in vitro on the d-β-hydroxybutyrate dehydrogenase (BDH) (EC 1.1.1.30) inner mitochondrial membrane enzyme. The results showed a high inhibition of BDH in terms of activity, protein expression and kinetic parameters. 相似文献