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191.
Morán-Zorzano MT Viale AM Muñoz FJ Alonso-Casajús N Eydallín GG Zugasti B Baroja-Fernández E Pozueta-Romero J 《FEBS letters》2007,581(5):1035-1040
Escherichia coli ADP-sugar pyrophosphatase (AspP) is a "Nudix" hydrolase that catalyzes the hydrolytic breakdown of ADP-glucose linked to glycogen biosynthesis. Moderate increases of AspP activity in the cell are accompanied by significant reductions of the glycogen content. In vitro analyses showed that AspP activity is strongly enhanced by macromolecular crowding and by both glucose-1,6-bisphosphate and nucleotide-sugars, providing a first set of indicative evidences that AspP is a highly regulated enzyme. To our knowledge, AspP is the sole bacterial enzyme described to date which is activated by both G1,6P(2) and nucleotide-sugars. 相似文献
192.
Sjöstrand D Carlsson J Paratcha G Persson B Ibáñez CF 《The Journal of biological chemistry》2007,282(17):12734-12740
Most plasma membrane proteins are capable of sensing multiple cell-cell and cell-ligand interactions, but the extent to which this functional versatility is founded on their modular design is less clear. We have identified the third immunoglobulin domain of the Neural Cell Adhesion Molecule (NCAM) as the necessary and sufficient determinant for its interaction with Glial Cell Line-derived Neurotrophic Factor (GDNF). Four charged contacts were identified by molecular modeling as the main contributors to binding energy. Their mutation abolished GDNF binding to NCAM but left intact the ability of NCAM to mediate cell adhesion, indicating that the two functions are genetically separable. The GDNF-NCAM interface allows complex formation with the GDNF family receptor alpha1, shedding light on the molecular architecture of a multicomponent GDNF receptor. 相似文献
193.
Stadthagen G Sambou T Guerin M Barilone N Boudou F Korduláková J Charles P Alzari PM Lemassu A Daffé M Puzo G Gicquel B Rivière M Jackson M 《The Journal of biological chemistry》2007,282(37):27270-27276
Mycobacteria produce two unusual polymethylated polysaccharides, the 6-O-methylglucosyl-containing lipopolysaccharides (MGLP) and the 3-O-methylmannose polysaccharides, which have been shown to regulate fatty acid biosynthesis in vitro. A cluster of genes dedicated to the synthesis of MGLP was identified in Mycobacterium tuberculosis and Mycobacterium smegmatis. Overexpression of the putative glycosyltransferase gene Rv3032 in M. smegmatis greatly stimulated MGLP production, whereas the targeted disruption of Rv3032 in M. tuberculosis and that of the putative methyltransferase gene MSMEG2349 in M. smegmatis resulted in a dramatic reduction in the amounts of MGLP synthesized and in the accumulation of precursors of these molecules. Disruption of Rv3032 also led to a significant decrease in the glycogen content of the tubercle bacillus, indicating that the product of this gene is likely to be involved in the elongation of more than one alpha-(1-->4)-glucan in this bacterium. Results thus suggest that Rv3032 encodes the alpha-(1-->4)-glucosyltransferase responsible for the elongation of MGLP, whereas MSMEG2349 encodes the O-methyltransferase required for the 6-O-methylation of these compounds. 相似文献
194.
Habitat fragmentation, variable edge effects, and the landscape-divergence hypothesis 总被引:2,自引:0,他引:2
Laurance WF Nascimento HE Laurance SG Andrade A Ewers RM Harms KE Luizão RC Ribeiro JE 《PloS one》2007,2(10):e1017
Edge effects are major drivers of change in many fragmented landscapes, but are often highly variable in space and time. Here we assess variability in edge effects altering Amazon forest dynamics, plant community composition, invading species, and carbon storage, in the world's largest and longest-running experimental study of habitat fragmentation. Despite detailed knowledge of local landscape conditions, spatial variability in edge effects was only partially foreseeable: relatively predictable effects were caused by the differing proximity of plots to forest edge and varying matrix vegetation, but windstorms generated much random variability. Temporal variability in edge phenomena was also only partially predictable: forest dynamics varied somewhat with fragment age, but also fluctuated markedly over time, evidently because of sporadic droughts and windstorms. Given the acute sensitivity of habitat fragments to local landscape and weather dynamics, we predict that fragments within the same landscape will tend to converge in species composition, whereas those in different landscapes will diverge in composition. This 'landscape-divergence hypothesis', if generally valid, will have key implications for biodiversity-conservation strategies and for understanding the dynamics of fragmented ecosystems. 相似文献
195.
196.
Mendes GD Hamamoto D Ilha J Pereira Ados S De Nucci G 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2007,850(1-2):553-559
A rapid, sensitive and specific method for quantifying the aromatase inhibitor (anastrozole) in human plasma using dexchlorpheniramine as the internal standard (I.S.) is described herein. The analyte and the I.S. were extracted from 200 microl of human plasma by liquid-liquid extraction using a mixture of diethyl ether:dichloromethane (70:30, v/v) solution. Extracts were removed and dried in the organic phase then reconstituted with 200 microl of acetonitrile:water (50:50; v/v). The extracts were analyzed by high performance liquid chromatography coupled with photospray tandem mass spectrometry (HPLC-MS-MS). Chromatography was performed isocratically on a Genesis, C18 4 microm analytical column (100 mm x 2.1mm i.d.). The method had a chromatographic run time of 2.5 min and a linear calibration curve ranging from 0.05-10 ng ml(-1). The limit of quantification (LOQ) was 0.05 ng ml(-1). This HPLC-MS-MS procedure was used to assess pharmacokinetic studies. 相似文献
197.
Leite ES Santana SR Hünenberger PH Freitas LC Longo RL 《Journal of molecular modeling》2007,13(9):1017-1025
The relative stabilities of the alkali [M ⊂ 222]+ cryptates (M = Na, K, Rb and Cs) in the gas phase and in solution (80:20 v/v methanol:water mixture) at 298 K, are computed
using a combination of ab initio quantum-chemical calculations (HF/6-31G and MP2/6-31+G*//HF/6-31+G*) and explicit-solvent
Monte Carlo free-energy simulations. The results suggest that the relative stabilities of the cryptates in solution are due
to a combination of steric effects (compression of large ions within the cryptand cavity), electronic effects (delocalization
of the ionic charge onto the cryptand atoms) and solvent effects (dominantly the ionic dessolvation penalty). Thus, the relative
stabilities in solution cannot be rationalized solely on the basis of a simple match or mismatch between the ionic radius
and the cryptand cavity size as has been suggested previously. For example, although the [K ⊂ 222]+ cryptate is found to be the most stable in solution, in agreement with experimental data, it is the [Na ⊂ 222]+ cryptate that is the most stable in the gas phase. The present results provide further support to the notion that the solvent
in which supramolecules are dissolved plays a key role in modulating molecular recognition processes.
Figure Alkali cryptates [M ⊂ 222]+ (M = Na, K, Rb and Cs) relative stabilities in gas and methanol:water solution: solvent effects
and molecular recognition
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
198.
Pereira LA Báo SN Barbosa MS da Silva JL Felipe MS de Santana JM Mendes-Giannini MJ de Almeida Soares CM 《FEMS yeast research》2007,7(8):1381-1388
Paracoccidioides brasiliensis is an important fungal pathogen. The disease it causes, paracoccidioidomycosis (PCM), ranges from localized pulmonary infection to systemic processes that endanger the life of the patient. Paracoccidioides brasiliensis adhesion to host tissues contributes to its virulence, but we know relatively little about molecules and the molecular mechanisms governing fungal adhesion to mammalian cells. Triosephosphate isomerase (TPI: EC 5.3.1.1) of P. brasiliensis (PbTPI) is a fungal antigen characterized by microsequencing of peptides. The protein, which is predominantly expressed in the yeast parasitic phase, localizes at the cell wall and in the cytoplasmic compartment. TPI and the respective polyclonal antibody produced against this protein inhibited the interaction of P. brasiliensis to in vitro cultured epithelial cells. TPI binds preferentially to laminin, as determined by peptide inhibition assays. Collectively, these results suggest that TPI is required for interactions between P. brasiliensis and extracellular matrix molecules such as laminin and that this interaction may play an important role in the fungal adherence and invasion of host cells. 相似文献
199.
200.