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991.
A simple mechanism for co-dependence on two activators at an Escherichia coli promoter 总被引:7,自引:0,他引:7
Joseph T. Wade Tamara A. Belyaeva Eva I. Hyde Stephen J.W. Busby 《The EMBO journal》2001,20(24):7160-7167
992.
Characterization of a New Operon, as-48EFGH, from the as-48 Gene Cluster Involved in Immunity to Enterocin AS-48 总被引:2,自引:0,他引:2 下载免费PDF全文
Marta Diaz Eva Valdivia Manuel Martínez-Bueno Matilde Fernndez Andrs Santos Soler-Gonzlez Hilario Ramírez-Rodrigo Mercedes Maqueda 《Applied microbiology》2003,69(2):1229-1236
Enterocin AS-48 is a cyclic peptide produced by Enterococcus faecalis S-48 whose genetic determinants have been identified in the conjugative plasmid pMB2. A region of 7.8 kb, carrying the minimum information required for production of and immunity against AS-48, had been previously cloned and sequenced in pAM401 (pAM401-52). In this region, the as-48A structural gene and as-48B, as-48C, as-48C1, as-48D, and as-48D1 genes and open reading frame 6 (ORF6) and ORF7 had been identified. The sequence analysis carried out in this work in the BglII B fragment (6.6-kb) from pMB2 cloned downstream from the last ORF identified (ORF7) revealed the existence of two new ORFs, as-48G and as-48H, necessary for full AS-48 expression. Thus, JH2-2 transformants obtained with the pAM401-81 plasmid became producers and resistant at the wild-type level. Tn5 disruption experiments in the last genes, as-48EFGH, were not able to reproduce these expression levels, confirming that expression of these genes is necessary to get the phenotype conferred by the wild-type pMB2 plasmid. The as-48EFGH operon encodes a new ABC transporter that could be involved in producer self-protection. On the basis of the observed similarities, As-48G would be the ATP-binding domain, the deduced amino acid sequences of As-48E and As48-H could be assigned as transmembrane subunits, and As-48F, with an N-terminal transmembrane segment and a coiled-coil domain, strongly resembles the structure of some known ABC transporter accessory proteins whose localization in the cell is discussed. This cluster of genes is expressed by two polycistronic mRNAs, T2 and T3, in JH2-2(pAM401-81) in coordinate expression. Our results also suggest that expression of T3 could be regulated, because in JH2-2(pAM401EH) transformants, T3 was not detected, suggesting that these genes do not by themselves confer immunity, in accordance with the requirement for the as-48D1 gene for immunity against AS-48. 相似文献
993.
Dr. Eva Black Liselotte Petersen Martin Kreutzer Søren Toubro Thorkild I. A. Sørensen Oluf Pedersen Arne Astrup 《Obesity (Silver Spring, Md.)》2002,10(2):69-77
Objective: To study the influence of scan velocities of DXA on the measured size of fat mass, lean body mass, bone mineral content and density, and total body weight. Research Methods and Procedures: The subjects were 71 healthy white adults, 38 women and 33 men. The mean age was 41.7 ± 13.5 years and body mass index was 28.6 ± 5.6 kg/m2. The subjects were scanned consecutively in slow, medium, and fast scan mode by a Lunar DPX-IQ DXA scanner. Results: Throughout the body mass index and sagittal height ranges, scanned lean body mass significantly decreased with higher scan velocity and lean body mass was 2.7% lower in fast than in medium mode (p < 0.0001). In contrast, fat mass, percentage of body fat, and bone mineral contents were higher with increasing scan velocity. Areas not analyzed by the scanner, so called blue spots, increased with scan velocity and sagittal height, and their presence significantly enhanced the error. Body weight estimated by DXA in slow mode was −0.8% lower than scale weight in the women (p < 0.001) and −0.2% in men (not significant), and the difference was greater with increasing scan velocity. Discussion: Scan velocity significantly influences the measured fat mass size, lean body mass, bone mineral content, and body weight. To obtain the most accurate results, slow mode is preferable and fast scans should be avoided. Future studies should report and take scan velocity into consideration. 相似文献
994.
T-DNA tagging in the model legume Medicago truncatula allows efficient gene discovery 总被引:3,自引:0,他引:3
Scholte Marije d'Erfurth Isabelle Rippa Sonia Mondy Samuel Cosson Viviane Durand Patricia Breda Colette Trinh Hanh Rodriguez-Llorente Ignacio Kondorosi Eva Schultze Michael Kondorosi Adam Ratet Pascal 《Molecular breeding : new strategies in plant improvement》2002,10(4):203-215
The annual legume Medicago truncatula has been proposed as a model plant to study various aspects of legume biology including rhizobial and mycorrhizal symbiosis because it is well suited for the genetic analysis of these processes . To facilitate the characterization of M. truncatula genes participating in various developmental processes we have initiated an insertion mutagenesis program in this plant using three different T-DNAs as tags. To investigate which type of vector is the most suitable for mutagenesis we compared the behavior of these T-DNAs. One T-DNA vector was a derivative of pBin19 and plant selection was based on kanamycin resistance. The two other vectors carried T-DNA conferring Basta resistance in the transgenic plants. For each T-DNA type, we determined the copy number in the transgenic lines, the structure of the T-DNA loci and the sequences of the integration sites. The T-DNA derived from pBin19 generated complex T-DNA insertion patterns. The two others generally gave single copy T-DNA inserts that could result in gene fusions for the pGKB5 T-DNA. Analysis of the T-DNA borders revealed that several M. truncatula genes were tagged in these transgenic lines and in vivo gus fusions were also obtained. These results demonstrate that T-DNA tagging can efficiently be used in M. truncatula for gene discovery. 相似文献
995.
Olga G?ransson Svante Resj? Lars R?nnstrand Vincent Manganiello Eva Degerman 《Cellular signalling》2002,14(2):175-182
The mechanism of activation for protein kinase B (PKB), an important target for insulin signaling, has been scarcely investigated in primary cells. In this study, we have characterized the insulin-induced phosphorylation and activation of PKB beta in primary rat adipocytes. Insulin stimulation resulted in a translocation of PKB beta from cytosol to membranes, and phosphorylation and activation of PKB beta. Phosphoamino acid analysis and phosphopeptide mapping demonstrated that the phosphorylation occurred mainly on serines, also when using calyculin A, and that these were localized within one major phosphopeptide. Radiosequencing showed that the radioactivity was released in Cycle No. 7. In addition, the peptide was specifically immunoprecipitated from a tryptic digest of PKB beta using the anti-phospho-PKB (Ser-473) antibody. Taken together, these results show that rat adipocyte PKB beta mainly is phosphorylated on Ser-474 in response to insulin stimulation, in contrast to previous studies in human embryonic kidney (HEK) 293 cells demonstrating, in addition, phosphorylation of Thr-309. 相似文献
996.
Melanie R. Nelson Eva Thulin Patricia A. Fagan Sture Forsn Walter J. Chazin 《Protein science : a publication of the Protein Society》2002,11(2):198-205
EF-hand Ca(2+)-binding proteins participate in both modulation of Ca(2+) signals and direct transduction of the ionic signal into downstream biochemical events. The range of biochemical functions of these proteins is correlated with differences in the way in which they respond to the binding of Ca(2+). The EF-hand domains of calbindin D(9k) and calmodulin are homologous, yet they respond to the binding of calcium ions in a drastically different manner. A series of comparative analyses of their structures enabled the development of hypotheses about which residues in these proteins control the calcium-induced changes in conformation. To test our understanding of the relationship between protein sequence and structure, we specifically designed the F36G mutation of the EF-hand protein calbindin D(9k) to alter the packing of helices I and II in the apoprotein. The three-dimensional structure of apo F36G was determined in solution by nuclear magnetic resonance spectroscopy and showed that the design was successful. Surprisingly, significant structural perturbations also were found to extend far from the site of mutation. The observation of such long-range effects provides clear evidence that four-helix EF-hand domains should be treated as a single globally cooperative unit. A hypothetical mechanism for how the long-range effects are transmitted is described. Our results support the concept of energetic and structural coupling of the key residues that are crucial for a protein's fold and function. 相似文献
997.
998.
Male SEC/1ReJ mice aged 6 or 17 months were fed diets containing 0, 2, 4 and 8% added phosphatidyl choline. After 4 days on the test diets they were given 5 daily sessions of 100 trials each in the shuttle-box. The younger mice rapidly acquired an avoidance response and reached high, stable levels of performance. The older mice learned more slowly and reached significantly lower performance levels (p < 0.01). Phosphatidyl choline had no effect on performance of young mice, while in the older mice the highest dose level of phosphatidyl choline increased avoidance performance by nearly 30% (p < 0.05). 相似文献
999.
1000.
Lubomí ra Rexov -Benkov Eva Stratilov Martin apka 《Biocatalysis and Biotransformation》1990,4(2):219-225
Endopolygalacturonase of Aspergillus sp. was immobilized by three different methods; viz. (a) via amino groups, (b) via carboxyl groups and (c) by means of epoxy groups to a nonporous microparticular silicon dioxide (Cabosil), functionalized by 3-(amino)-propyl groups and 3-(2',3'-epoxypropoxy)-propyl groups, respectively. The conjugates were compared in their mode of action with corresponding immobilized preparations based on microporous ceramics. The binding via amino groups and via carboxyl groups lead, by itself, to changes in the mode of action of the enzyme, consisting of a decrease in randomness of glycosidic linkage splitting. The changes were greater in microporous support conjugates due to additional size-exclusion effects. The action pattern of endopolygalacturonase bound by means of epoxy groups was modulated exclusively by the porosity of the support, whereas the binding alone did not play any role. 相似文献