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101.
102.
The accumulation of pre-PhoS under conditions of PhoS overproduction has been previously described. It is now demonstrated that during the induction of PhoS, a delay in the completion of polypeptide chain elongation can be detected. This delay is related to the extent of jamming of export sites by pre-PhoS or by other exported proteins. These results suggest that a component required for completion of pre-PhoS polypeptide becomes limiting, being titrated by the excess of nascent chains bearing signal peptides. This component thus probably acts at an early step in the export pathway. 相似文献
103.
Precise localization of an overproduced periplasmic protein in Escherichia coli: use of double immuno-gold labelling 总被引:2,自引:0,他引:2
A Bernadac J M Bolla C Lazdunski M Inouye J M Pages 《Biology of the cell / under the auspices of the European Cell Biology Organization》1987,61(3):141-147
The subcellular localization of beta-lactamase produced by a secretion-cloning vector pIN-III was studied by immunolabelling of frozen thin sections of Escherichia coli. Using double immuno-gold detections and internal reference proteins, it is shown here that beta-lactamase encoded by this vector can be exported and that its overproduction leads to aggregation within the periplasm. This aggregation induces the appearance of electron-dense areas immunolabelled by the antiserum directed against the beta-lactamase at the external side of the cytoplasmic membrane. The overproduced enzyme is also secreted to the medium in vesicles budding from the outer membrane of lpp strains. 相似文献
104.
105.
Noujeim E Khater C Pages S Ogier JC Tailliez P Hamze M Thaler O 《Journal of invertebrate pathology》2011,107(1):82-85
A survey of entomopathogenic nematodes in Lebanon was conducted for the first time during 2008-2009. Samples were collected on the coastal strip and in nine vegetation types extending from the coastal line to 3088 m above sea level. Wooded and herbaceous ecosystems were considered for sampling purposes. A total of 570 samples were taken, out of which 1% were positive for entomopathogenic nematodes. Approximately, 15.8% out of the 19 sites sampled revealed entomopathogenic nematodes presence (representing three samples). Two entomopathogenic nematodes species Heterorhabditis bacteriophora and Steinernema feltiae were recovered, and identification of their symbiotic bacteria revealed the presence of a Xenorhabdus bovienii, Photorhabdus temperata subsp. thracensis, Photorhabdus luminescens subsp. kayaii and Photorhabdus luminescens subsp. Laumondii. 相似文献
106.
Stéphanie Dupuy Marion Lambert David Zucman Siméon-Pierre Choukem Sara Tognarelli Cécile Pages Céleste Lebbé Sophie Caillat-Zucman 《PLoS pathogens》2012,8(1)
The contribution of innate immunity to immunosurveillance of the oncogenic Human Herpes Virus 8 (HHV8) has not been studied in depth. We investigated NK cell phenotype and function in 70 HHV8-infected subjects, either asymptomatic carriers or having developed Kaposi''s sarcoma (KS). Our results revealed substantial alterations of the NK cell receptor repertoire in healthy HHV8 carriers, with reduced expression of NKp30, NKp46 and CD161 receptors. In addition, down-modulation of the activating NKG2D receptor, associated with impaired NK-cell lytic capacity, was observed in patients with active KS. Resolution of KS after treatment was accompanied with restoration of NKG2D levels and NK cell activity. HHV8-latently infected endothelial cells overexpressed ligands of several NK cell receptors, including NKG2D ligands. The strong expression of NKG2D ligands by tumor cells was confirmed in situ by immunohistochemical staining of KS biopsies. However, no tumor-infiltrating NK cells were detected, suggesting a defect in NK cell homing or survival in the KS microenvironment. Among the known KS-derived immunoregulatory factors, we identified prostaglandin E2 (PGE2) as a critical element responsible for the down-modulation of NKG2D expression on resting NK cells. Moreover, PGE2 prevented up-regulation of the NKG2D and NKp30 receptors on IL-15-activated NK cells, and inhibited the IL-15-induced proliferation and survival of NK cells. Altogether, our observations are consistent with distinct immunoevasion mechanisms that allow HHV8 to escape NK cell responses stepwise, first at early stages of infection to facilitate the maintenance of viral latency, and later to promote tumor cell growth through suppression of NKG2D-mediated functions. Importantly, our results provide additional support to the use of PGE2 inhibitors as an attractive approach to treat aggressive KS, as they could restore activation and survival of tumoricidal NK cells. 相似文献
107.
A single specimen of the Antarctic anthomedusan Russellia mirabilisKramp 1957 has recently been collected in the AlboránSea. This is the first record for an Antarctic epipelagic organismin the Mediterranean Sea. Transport in the ballast water ofa cargo ship seems the most plausible mechanism for explainingthis rare occurrence. However, an alternative hypothesis isexplored involving a possibly complex medusan life cycle togetherwith the role of Antarctic (Intermediate and Bottom) water asdispersal mechanisms. 相似文献
108.
Cytoplasmic and periplasmic expression of a synthetic gene for ferredoxin in Escherichia coli 总被引:1,自引:0,他引:1
J P Bourdineaud S P Howard J M Pages A Bernadac G Leroy M Bruschi C Lazdunski 《Biochimie》1990,72(6-7):407-415
A synthetic gene coding for a modified ferredoxin II of Desulfovibrio desulfuricans Norway strain was assembled from 10 oligonucleotides. This gene was cloned into various expression vectors allowing either cytoplasmic expression or export to the periplasmic space. In the latter case, two different constructs were made, each of which contained the OmpA signal peptide: one of these constructs contained 3 additional N-terminal amino acids as compared to the wild-type ferredoxin (56 amino acid residues). The expression of proteins encoded by the 3 constructs was assayed in E coli and the proteins were localized by cell fractionation and immunogold labelling. A low percentage of the periplasmic ferredoxin (approximately 5%) was secreted to the medium in the absence of cell lysis. The recombinant ferredoxin was purified and found to be correctly processed by the leader peptidase. However, due to the high cysteine content intramolecular and intermolecular disulfide bonds were formed and prevented binding of [4Fe-4S] clusters. Reconstitution experiments using these recombinant proteins are in progress. 相似文献
109.
Guilhem Pages Allan M. Torres Pengchu Ju Paramjit S. Bansal Paul F. Alewood Philip W. Kuchel Jamie I. Vandenberg 《European biophysics journal : EBJ》2009,39(1):111-120
The hERG K+ channel undergoes rapid inactivation that is mediated by ‘collapse’ of the selectivity filter, thereby preventing ion conduction.
Previous studies have suggested that the pore-helix of hERG may be up to seven residues longer than that predicted by homology
with channels with known crystal structures. In the present work, we determined structural features of a peptide from the
pore loop region of hERG (residues 600–642) in both sodium dodecyl sulfate (SDS) and dodecyl phosphocholine (DPC) micelles
using NMR spectroscopy. A complete structure calculation was done for the peptide in DPC, and the localization of residues
inside the micelles were analysed by using a water-soluble paramagnetic reagent with both DPC and SDS micelles. The pore-helix
in the hERG peptide was only two–four residues longer at the N-terminus, compared with the pore helices seen in the crystal
structures of other K+ channels, rather than the seven residues suggested from previous NMR studies. The helix in the peptide spanned the same residues
in both micellar environments despite a difference in the localization inside the respective micelles. To determine if the
extension of the length of the helix was affected by the hydrophobic environment in the two types of micelles, we compared
NMR and X-ray crystallography results from a homologous peptide from the voltage gated potassium channel, KcsA. 相似文献
110.
A Allardet-Servent G Bourg M Ramuz M Pages M Bellis G Roizes 《Journal of bacteriology》1988,170(10):4603-4607
Preparations of DNA from 23 Brucella strains including 19 reference strains were compared by restriction endonuclease analysis. Pulsed-field gel electrophoresis resulted in optimal resolution of fragments generated by digestion with low-cleavage-frequency restriction enzymes such as XbaI. By this technique, five electrophoretypes were distinguished in five reference strains of the different species, i.e., B. abortus, B. melitensis, B. suis, B. canis, and B. ovis. Minor profile differences allowed us to discriminate between most biovars within a species. However, the differences in the DNA patterns of different field strains of biovar 2 of B. melitensis were not sufficient to serve as markers for epidemiological studies. From the XbaI fragments, we were able to estimate the size of the genomes of B. abortus 544T and B. melitensis 16 MT. This method revealed a relationship between DNA fingerprints, species, and pathovars which could shed light on problems concerning the classification and evolution of members of the genus Brucella. 相似文献