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101.
Tian Y Cuneo MJ Changela A Höcker B Beese LS Hellinga HW 《Protein science : a publication of the Protein Society》2007,16(10):2240-2250
We report the design and engineering of a robust, reagentless fluorescent glucose biosensor based on the periplasmic glucose-binding protein obtained from Thermotoga maritima (tmGBP). The gene for this protein was cloned from genomic DNA and overexpressed in Escherichia coli, the identity of its cognate sugar was confirmed, ligand binding was studied, and the structure of its glucose complex was solved to 1.7 Angstrom resolution by X-ray crystallography. TmGBP is specific for glucose and exhibits high thermostability (midpoint of thermal denaturation is 119 +/- 1 degrees C and 144 +/- 2 degrees C in the absence and presence of 1 mM glucose, respectively). A series of fluorescent conjugates was constructed by coupling single, environmentally sensitive fluorophores to unique cysteines introduced by site-specific mutagenesis at positions predicted to be responsive to ligand-induced conformational changes based on the structure. These conjugates were screened to identify engineered tmGBPs that function as reagentless fluorescent glucose biosensors. The Y13C*Cy5 conjugate is bright, gives a large response to glucose over concentration ranges appropriate for in vivo monitoring of blood glucose levels (1-30 mM), and can be immobilized in an orientation-specific manner in microtiter plates to give a reversible response to glucose. The immobilized protein retains its response after long-term storage at room temperature. 相似文献
102.
Ruiz L Sánchez B Ruas-Madiedo P de Los Reyes-Gavilán CG Margolles A 《FEMS microbiology letters》2007,274(2):316-322
Bifidobacterium animalis ssp. lactis is a probiotic frequently used as adjunct culture in fermented dairy products. In order to ensure its proper function at the intestinal level, this bacterium has to be tolerant to physiological concentrations of bile. This study examined the influence of bile on the fatty acid composition and the membrane characteristics of B. animalis IPLA 4549 and its mutant with acquired resistance to bile, B. animalis 4549dOx. Bile adaptation triggers in B. animalis 4549dOx a decrease in membrane fluidity and in the protein : phospholipid ratio, as well as a shift in the fatty acid composition of the cell. Remarkably, the presence of bile in the growth medium induced similar changes in both B. animalis cells. Furthermore, transmission electron microscopy analysis showed that bile promotes a severe distortion of the cell surface. This study provides new insights of the action of bile on the cell envelope of bifidobacteria. 相似文献
103.
Rigano LA Siciliano F Enrique R Sendín L Filippone P Torres PS Qüesta J Dow JM Castagnaro AP Vojnov AA Marano MR 《Molecular plant-microbe interactions : MPMI》2007,20(10):1222-1230
The phytopathogenic bacterium Xanthomonas axonopodis pv. citri is responsible for the canker disease affecting citrus plants throughout the world. Here, we have evaluated the role of bacterial attachment and biofilm formation in leaf colonization during canker development on lemon leaves. Crystal violet staining and confocal laser scanning microscopy analysis of X. axonopodis pv. citri strains expressing the green fluorescent protein were used to evaluate attachment and biofilm formation on abiotic and biotic (leaf) surfaces. Wild-type X. axonopodis pv. citri attached to and formed a complex, structured biofilm on glass in minimal medium containing glucose. Similar attachment and structured biofilm formation also were seen on lemon leaves. An X. axonopodis pv. citri gumB mutant strain, defective in production of the extracellular polysaccharide xanthan, did not form a structured biofilm on either abiotic or biotic surfaces. In addition, the X. axonopodis pv. citri gumB showed reduced growth and survival on leaf surfaces and reduced disease symptoms. These findings suggest an important role for formation of biofilms in the epiphytic survival of X. axonopodis pv. citri prior to development of canker disease. 相似文献
104.
Seed dispersal can severely limit the quantity of plant recruits and their spatial distribution. However, our understanding of the role of dispersal in regeneration dynamics is limited by the lack of knowledge of seed deposition patterns in space and time. In this paper, we analyse the spatiotemporal variability of seed dispersal patterns in the Mediterranean maple, Acer opalus subsp. granatense, by monitoring seed rain along two years at a broad spatial scale (2 mountain ranges, 2 populations per range, 4 microhabitats per population). We quantified seed limitation and its components (source and dispersal limitation), and explored dispersal limitation in space by analysing dispersal distances, seed aggregation, and microhabitat seed distribution. Acer opalus subsp. granatense was strongly seed‐limited throughout the gradients explored, being always dispersal limitation much higher than source limitation. The distribution of seeds with distance from adult individuals was leptokurtic and right‐skewed in all populations, being both kurtosis and skewness higher the year of the highest seed production. Dispersal distances were shorter than expected by random in the four populations, which suggests distance‐limited dispersal. Dispersal patterns were highly aggregated and showed a preferential direction around adults. At the microhabitat scale, most seeds accumulated under adult maples. However, there were no more seeds under trees and shrubs other than maple than in open interspaces, implying that established vegetation does not disrupt patterns of seed deposition by physically trapping seeds. When compared with patterns of seedling establishment, limited dispersal ability and inter‐annual spatial concordance in seed rain patterns suggest that several potentially safe sites for recruitment have a very low probability of receiving seeds in most maple populations. These findings are especially relevant for rare species such as Acer opalus subsp. granatense, and illustrate how dispersal studies are not only crucial for our understanding of plant population dynamics but also to provide conservation directions. 相似文献
105.
Juliana Stein Silvina C. Pessino Eric J. Martínez María Pía Rodriguez Lorena A. Siena Camilo L. Quarin Juan Pablo Amelio Ortiz 《Molecular breeding : new strategies in plant improvement》2007,20(2):153-166
Paspalum notatum Flügge is a warm-season forage grass with mainly diploid (2n = 20) and autotetraploid (2n = 40) representatives. Diploid
races reproduce sexually and require crosspollination due to a self-incompatible mating system, while autotetraploids reproduce
by aposporous apomixis. The objectives of this work were to develop a genetic linkage map of Paspalum notatum Flügge at the tetraploid level, identify the linkage/s group/s associated with apomixis and carry out a general characterization
of its mode of inheritance. A pseudo test-cross F1 family of 113 individuals segregating for the mode of reproduction was obtained by crossing a synthetic completely sexual
tetraploid plant (Q4188) as female parent with a natural aposporous individual (Q4117) as pollen donor. Map construction was
based on single-dose markers (SDAFs) segregating from both parents. Two linkage maps (female and male) were constructed. Within
each map, homologous groups were assembled by detecting repulsion-phase linked SDAFs. Putative Q4188 and Q4117 homolog groups
were identified by mapping shared single dose markers (BSDF). The Q4188 map consisted of 263 markers distributed on 26 co-segregation
groups over a total genetic distance of 1.590.6 cM, while the Q4117 map contained 216 loci dispersed on 39 co-segregation
groups along 2.265.7 cM, giving an estimated genome coverage of 88% and 83%, respectively. Seven and 12 putative homologous
chromosomes were detected within Q4188 and Q4117 maps, respectively. Afterward, ten female and male homologous chromosomes
were identified by mapping BSDFs. In the Q4117 map, a single linkage group was associated with apospory. It was characterized
by restriction in recombination and preferential chromosome pairing. A BPSD marker mapping within this group allowed the detection
of the female homolog and the putative four male groups of the set carrying apospory. 相似文献
106.
The Identification of Maize and Arabidopsis Type I FLAVONE SYNTHASEs Links Flavones with Hormones and Biotic Interactions 总被引:1,自引:0,他引:1
107.
Anthony Leyme Arthur Marivin Lorena Perez-Gutierrez Lien T. Nguyen Mikel Garcia-Marcos 《The Journal of cell biology》2015,210(7):1165-1184
Signal transduction via integrins and G protein–coupled receptors is critical to control cell behavior. These two receptor classes have been traditionally believed to trigger distinct and independent signaling cascades in response to extracellular cues. Here, we report a novel mechanism of integrin signaling that requires activation of the trimeric G protein Gαi by the nonreceptor guanine nucleotide exchange factor (GEF) GIV (also known as Girdin), a metastasis-associated protein. We demonstrate that GIV enhances integrin-dependent cell responses upon extracellular matrix stimulation and makes tumor cells more invasive. These responses include remodeling of the actin cytoskeleton and PI3K-dependent signaling, resulting in enhanced haptotaxis and invasion. We show that both GIV and its substrate Gαi3 are recruited to active integrin complexes and that tumor cells engineered to express GEF-deficient GIV fail to transduce integrin signals into proinvasive responses via a Gβγ-PI3K axis. Our discoveries delineate a novel mechanism by which integrin signaling is rewired during metastasis to result in increased tumor invasiveness. 相似文献
108.
Pehuén Pereyra Gerber Mercedes Cabrini Carolina Jancic Luciana Paoletti Claudia Banchio Catalina von Bilderling Lorena Sigaut Lía I. Pietrasanta Gabriel Duette Eric O. Freed Genevieve de Saint Basile Catarina Ferreira Moita Luis Ferreira Moita Sebastian Amigorena Philippe Benaroch Jorge Geffner Matías Ostrowski 《The Journal of cell biology》2015,209(3):435-452
During the late stages of the HIV-1 replication cycle, the viral polyprotein Pr55Gag is recruited to the plasma membrane (PM), where it binds phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) and directs HIV-1 assembly. We show that Rab27a controls the trafficking of late endosomes carrying phosphatidylinositol 4-kinase type 2 α (PI4KIIα) toward the PM of CD4+ T cells. Hence, Rab27a promotes high levels of PM phosphatidylinositol 4-phosphate and the localized production of PI(4,5)P2, therefore controlling Pr55Gag membrane association. Rab27a also controls PI(4,5)P2 levels at the virus-containing compartments of macrophages. By screening Rab27a effectors, we identified that Slp2a, Slp3, and Slac2b are required for the association of Pr55Gag with the PM and that Slp2a cooperates with Rab27a in the recruitment of PI4KIIα to the PM. We conclude that by directing the trafficking of PI4KIIα-positive endosomes toward the PM, Rab27a controls PI(4,5)P2 production and, consequently, HIV-1 replication. 相似文献
109.
110.