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21.
Competence pheromone, oligopeptide permease, and induction of competence in Streptococcus pneumoniae 总被引:5,自引:4,他引:1
Geneviève Alioing Chantal Granadel Donald A. Morrison Jean-Pierre Claverys 《Molecular microbiology》1996,21(3):471-478
An unmodified heptadecapeptide pheromone capable of eliciting competence for genetic transformation in Streptococcus pneumoniae has recently been identified and characterized. In considering possible signaltransduction mechanisms for the peptide, the previously characterized Ami oligopeptide permease and the three highly homologous oligopeptide-binding lipoproteins, AmiA. AliA, and AliB, appeared to be good candidates for receptors. We therefore compared the spontaneous transformability of Ami, AliA and AliB mutants to that of an isogenic wild-type strain and we investigated the response of the various mutants to treatment with synthetic competence-stimulating peptide (CSP). Our results clearly demonstrate that neither Ami nor any of the three highly homologous oligopeptide-binding lipoproteins identified so far in S. pneumoniae are required for competence induction following treatment with synthetic CSP. Although the existence of a fourth unidentified oligopeptide-binding lipoprotein and/or a second oligopeptide permease operon could not be completely ruled out, we favour the hypothesis that CSP signal transmission rather involves a two-component regulatory system. Although none of the single or double Ami and Ali mutants tested appeared severely affected for competence, an exceptional aliB plasmid-insertion mutation abolished competence completely. In addition, the triple AmiA-AliA-AliB mutant differed from wild type in showing no sharp peak of competence but exhibiting transformability throughout the exponential phase of growth. These and previous observations are discussed and a general hypothesis is proposed to account for the modulation of competence by peptide permease mutants in S. pneumoniae. 相似文献
22.
Lorenz Schmid Michel Bottlaender Chantal Fuseau Denis Fournier Emmanuel Brouillet Mariannick Mazire 《Journal of neurochemistry》1995,65(4):1880-1886
Abstract: The distinctive pharmacological activity of zolpidem in rats compared with classical benzodiazepines has been related to its differential affinity for benzodiazepine receptor (BZR) subtypes. By contrast, in nonhuman primates the pharmacological activity of zolpidem was found to be quite similar to that of classical BZR agonists. In an attempt to explain this discrepancy, we examined the ability of zolpidem to differentiate BZR subtypes in vivo in primate brain using positron emission tomography. The BZRs were specifically labeled with [11C]flumazenil. Radiotracer displacement by zolpidem was monophasic in cerebellum and neocortex, with in vivo Hill coefficients close to 1. Conversely, displacement of [11C]flumazenil was biphasic in hippocampus, amygdala, septum, insula, striatum, and pons, with Hill coefficients significantly smaller than 1, suggesting two different binding sites for zolpidem. In these cerebral regions, the half-maximal inhibitory doses for the high-affinity binding site were similar to those found in cerebellum and neocortex and ~100-fold higher for the low-affinity binding site. The low-affinity binding site accounted for <32% of the specific [11C]-flumazenil binding. Such zolpidem binding characteristics contrast with those reported for rodents, where three different binding sites were found. Species differences in binding characteristics may explain why zolpidem has a distinctive pharmacological activity in rodents, whereas its pharmacological activity in primates is quite similar to that of classical BZR agonists, except for the absence of severe effects on memory functions, which may be due to the lack of substantial zolpidem affinity for a distinct BZR subtype in cerebral structures belonging to the limbic system. 相似文献
23.
H. de Verneuil B. Grandchamp Chantal Foubert Dominique Weil Cong Van N'Guyen Marie-Sylvie Gross Shigeru Sassa Y. Nordmann 《Human genetics》1984,66(2-3):202-205
Summary A specific enzyme immunoassay of uroporphyrinogen decarboxylase was developed and applied to the detection of the human enzyme in man-rodent somatic cell hybrids. This method allowed to assign the gene for uroporphyrinogen decarboxylase to human chromosome 1. 相似文献
24.
Dominique Weil Nguyen Van-Cong Catherine Finaz R. Rebourcet Chantal Cochet J. de Grouchy J. Frézal 《Human genetics》1977,36(2):205-211
Summary 22 independent man-hamster (HGPRT–) hybrids using male human cells with balanced reciprocal translocation t(X;2)(p22;q32) were analysed for human genes localized on chromosome 2 (IDHS, MDHS), on chromosome X (PGK, GAL, G6PD) and for the different chromosomes in relation with the balanced reciprocal translocation (chr.2, chr.2q–, chr.Xp+).The following results were obtained:The chromosomes 2 and 2q– are absent in the 22 hybrids.In 9 hybrids, the absence of MDHS in spite of the presence of the chromosome Xp+ indicates that the gene for MDHS is not localized on this chromosome (or that the gene for MDHS is not on the segment 2q32-2qter translocated on X).In 14 hybrids, the three markers of X (PGK, GAL, G6PD) and IDHS are expressed in the presence of the chromosome Xp+. This result indicates that the genes for these markers are on Xp+ or that the genes PGK, GAL, G6PD are on X without the Xp22-Xter segment, translocated on the chr.2, and that the gene for IDHS is on the 2q32-2qter segment translocated on X.In 8 hybrids, in the absence of the intact chromosome Xp+, the higher percentage of the presence of G6PD (7 hybrids) and the lower percentage of the presence of IDHS (3 hybrids) are explained by the fact that these hybrids selected in HAT medium had to retain a segment of Xp+ bearing the human gene HGPRT. G6PD appeared very close to HGPRT and IDHS very distant from HGPRT.The study of the different correlations between the presence and the absence of these four markers on Xp+ in the different hybrids indicates the following order on the chromosome Xp+ from p to q: IDHs — PGK — GAL — G6PD.
Groupe INSERM: Directeur J. Frézal
Groupe CNRS, ER, 149: Directeur J. de Grouchy 相似文献
Groupe INSERM: Directeur J. Frézal
Groupe CNRS, ER, 149: Directeur J. de Grouchy 相似文献
25.
Abstract— Cortical monoamine changes during ischemic episodes of varied duration and their sequence of changes following cerebral reperfusion were studied in the gerbil. Forty-one percent of 280 animals exhibited signs of cerebral hemispheric ischemia (stroke) after unilateral common carotid artery occlusion. Norepinephrine (NE) levels decreased after 60 min in the occluded hemisphere of stroked animals but dopamine (DA) levels were unaltered. S-Hydroxytryptamine (5-HT) levels became bilaterally reduced in both stroked and non-stroked animals as soon as S min after occlusion. Upon reperfusion after periods of 30 or 60 min of occlusion there was a bilateral rebound increase of cortical NE and DA levels to well above control values in stroked and non-stroked animals. 5-HT levels remained reduced in both groups. Results suggest disorder of monoamine metabolism in ischemic brain which persists during the early reperfusion period, perhaps contributing to deficits in neurological function. Monoamine changes in contralateral non-ischemic hemispheres both during the occlusion and reperfusion periods are thought further evidence of diaschisis. 相似文献
26.
Characterization of exoglucanase and synergistic hydrolysis of cellulose in Clostridium stercorarium
Abstract A cellobiohydrolase component was isolated from an anaerobic thermophilic cellulolytic bacterium, Clostridium stercorarium . When acting alone, the enzyme showed minimal activity towards ordered substrates such as cellulose and filter paper but it has been shown to attack phosphoric-acid swollen cellulose giving cellobiose as principal product. When recombined with endoglucanase it did allow an extensive hydrolysis demonstrating a marked synergism in the action of those two components; the addition of β-glucosidase resulted in a further increase in activity. 相似文献
27.
Pierre Abad Chantal Quiles Sophie Tares Christine Piotte Philippe Castagnose-Sereno Monique Abadon Antoine Dalmasso 《Journal of molecular evolution》1991,33(3):251-258
Summary To have a better understanding of the evolutionary history of mobile elements within the nematodes, we examined the distribution and the conservation of homologues to transposable elements fromCaenorhabditis elegans (Tc1, Tc2, Tc3, Tc4, Tc5, and FB1) in 19 nematode species belonging to the class Secernentea. Our results show that Tc1 elements display a distribution restricted to the family Rhabditidae with poor conservation. The Tc2 and FB1 homologous elements have the same patchy distribution within the Rhabditidae. They were only found inCaenorhabditis and inTeratorhabditis. The Tc3 element is widely distributed among nematode species. Tc3 homologous elements are present in the majority of the Rhabditidae but also in two genera within the family Panagrolaimidae, and inBursaphelenchus, which belongs to the order Aphelenchida. Tc4 and Tc5 homologues show the most limited distribution of all tested elements, being strictly limited toC. elegans. These data indicate that in some cases, the distribution of transposable elements in the nematode cannot be explained by strict vertical transmission. The distribution of Tc3, Tc4, and Tc5 suggests that horizontal transmission may have occurred between reproductively isolated species during their evolutionary history. 相似文献
28.
Damian Labuda Daniel Sinnett Chantal Richer Jean-Marc Deragon George Striker 《Journal of molecular evolution》1991,32(5):405-414
Summary In a recent report mouse B1 genomic repeats were divided into six families representing different waves of fixation of B1 variants, consistent with the retroposition model of human Alu elements. These data are used to examine the distribution of nucleotide substitutions in individual genomic repeats with respect to family consensus sequences and to compare the minimal energy structures of the corresponding B1 RNAs. By an enzymatic approach the predicted structure of B1 RNAs is experimentally confirmed using as a model sequence an RNA of a young B1 family member transcribed in vitro by T7 RNA polymerase. B1 RNA preserves folding domains of the Alu fragment of 7SL RNA, its progenitor molecule. Our results reveal similarities among 7SL-like retroposons, human Alu, and rodent B1 repeats, and relate the evolutionary conservation of B1 family consensus sequences to selection at the RNA level. 相似文献
29.
This study presents data of in situ measurements of inorganic carbon assimilation by phytoplankton communities of the St Lawrence estuary during the end of summer 1982. We used carboxylase activity measurements (ribulose-1,5-bisphosphate carboxylase, carboxylases) and the 13C/12C ratio of phytoplankton organic carbon, expressed as 13C, to study patterns of assimilation. Upper estuary phytoplankton communities showed a smaller turn-over rate in carbon assimilation than lower estuary phytoplankton communities. Carbon assimilation was limited by light intensity in the upper estuary and by CO2 availability in the lower estuary. In the St Lawrence estuary, stable carbon isotope ratios of phytoplankton organic carbon seemed to be controlled by inorganic carbon availability rather than by phytoplankton metabolism. 相似文献
30.
Chantal Jeanne Beauchamp William Scott Chilton Patrice Dion Hani Antoun 《Applied microbiology》1990,56(1):150-155
This study was conducted to determine the capacities of 37 fungi to utilize various crown gall opines as their sole carbon and nitrogen source. One strain of Fusarium solani, two of Cylindrocarpon destructans, and six of Cylindrocarpon heteronema catabolized octopine, mannopine, octopinic acid, succinamopine, or a combination of these opines. One C. heteronema and one Fusarium dimerum strain grew only on succinamopine. None of the fungal isolates had the ability to grow on nopaline. The catabolism of opines by fungi was confirmed by the disappearance of the opine from the growth medium and by an increase in final mycelial dry weight with rising initial concentration of test substrate. This study thus shows that the catabolism of opines is not restricted to bacteria. 相似文献