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171.
The growth of the biotrophic pathogen Cladosporium fulvum within the tomato (Lycopersicon esculentum Mill.) leaf is restricted to the intercellular space. Previous studies from this laboratory have demonstrated that gamma-aminobutyric acid (GABA) accumulates to millimolar concentrations in the apoplast during a compatible interaction. We decided to further investigate the role of GABA during infection. A gene encoding a required enzyme for GABA metabolism, GABA transaminase (Gat1), was cloned and sequenced from C. fulvum. The predicted protein sequence of Gat1 had high homology to other fungal GABA transaminases, particularly from Aspergillus nidulans. In vitro expression experiments revealed Gat1 to be strongly expressed during fungal growth on both GABA and glutamate whereas nearly no expression was evident during nitrogen starvation conditions. Expression of Gat1 was also apparent during infection, suggesting for the first time that C. fulvum actively metabolises GABA during infection. This indicates that the fungus may be utilising the GABA in the apoplast as a nutrient source. Further analysis revealed that the expression of tomato glutamate decarboxylase, the enzyme responsible for GABA synthesis, appeared appreciably higher during a compatible interaction than in the incompatible interaction. These findings imply that the infecting fungus may alter the physiology of the tomato leaf with the result that a source of nitrogen is supplied. 相似文献
172.
Hung CS Bouckaert J Hung D Pinkner J Widberg C DeFusco A Auguste CG Strouse R Langermann S Waksman G Hultgren SJ 《Molecular microbiology》2002,44(4):903-915
The first step in the colonization of the human urinary tract by pathogenic Escherichia coli is the mannose-sensitive binding of FimH, the adhesin present at the tip of type 1 pili, to the bladder epithelium. We elucidated crystallographically the interactions of FimH with D-mannose. The unique site binding pocket occupied by D-mannose was probed using site-directed mutagenesis. All but one of the mutants examined had greatly diminished mannose-binding activity and had also lost the ability to bind human bladder cells. The binding activity of the mono-saccharide D-mannose was delineated from this of mannotriose (Man(alpha 1-3)[Man(alpha 1-6)]Man) by generating mutants that abolished D-mannose binding but retained mannotriose binding activity. Our structure/function analysis demonstrated that the binding of the monosaccharide alpha-D-mannose is the primary bladder cell receptor for uropathogenic E. coli and that this event requires a highly conserved FimH binding pocket. The residues in the FimH mannose-binding pocket were sequenced and found to be invariant in over 200 uropathogenic strains of E. coli. Only enterohaemorrhagic E. coli (EHEC) possess a sequence variation within the mannose-binding pocket of FimH, suggesting a naturally occurring mechanism of attenuation in EHEC bacteria that would prevent them from being targeted to the urinary tract. 相似文献
173.
174.
Frontier molecular orbital (FMO) theory coupled with density functional calculations has been applied to investigate the chemical reactivity of three key bioinorganic Cu(n)-O(2) complexes, the mononuclear end-on hydroperoxo-Cu(II), the side-on bridged mu-eta(2):eta(2)-O(2)(2-) Cu(II)(2) dimer and the bis-mu-oxo Cu(III)(2) dimer. Two acceptor orbitals (sigma* and pi*) of each complex and two types of donating substrates (sigma-substrate, phosphine; pi-substrate, alkylbenzene) are considered in the electrophilic attack mechanism. The angular dependences of different reaction pathways are determined using FMO theory and the angular overlap model. Including steric effects, the sigma*/sigma and pi*/pi pathways are found more reactive than the corresponding cross sigma*/pi and pi*/sigma pathways which have poor donor-acceptor orbital overlaps in the sterically constrained substrate access region. 相似文献
175.
176.
In the present study, a soil microfungal community was examined over a one-year period (1999–2000) at the western shore of
the Dead Sea. A total of 78 species from 40 genera were isolated. The most prominent features of mycobiota of the territory
studied were: (i) the prevailing number of melanin-containing micromycetes (46 species, 65.5 % of the total isolate number);
(ii) a large share of teleomorphic Ascomyceta (26 species, 18.5 % of isolates); (iii) combination of true soil and plant surface
inhabiting species; (iv) spatial and temporal variation of the mycobiota composition; (v) very low fungal density (nearly
500-fold lower than in the Judean Desert soil). These features are formed under the extremely stressful xeric and oligotrophic
conditions in which the Dead Sea coastal micromycete community exists. Nine species (Alternaria alternata, A. raphani, Aspergillus niger, Aureobasidium pullulans, Chaetomium globosum, Ch. murorum, Cladosporium
cladosporioides, Penicillium aurantiogriseum, and Stachybotrys chartarum) were considered a characteristic micromycete complex for the Dead Sea coastal habitat based on the spatial and temporal
occurrence of these species. Many of the micromycetes isolated, including almost all the species listed above, are known to
be distributed worldwide occurring in different soil types. This confirms the conclusion of many mycologists working in areas
with saline and arid soils that there is no halo-and thermophilous mycobiota characteristic for those soils. 相似文献
177.
Bioethics: power and injustice: IAB presidential address 总被引:1,自引:0,他引:1
Benatar SR 《Bioethics》2003,17(5-6):387-399
A major focus within the modern bioethics debate has been on reshaping power relationships within the doctor-patient relationship. Empowerment of the vulnerable has been achieved through an emphasis on human rights and respect for individual dignity. However, power imbalances remain pervasive within healthcare. To a considerable extent this relates to insufficient attention to social injustice. Such power imbalances together with the development of new forms of power, for example through new genetic biotechnology, raise the spectre of increasing social injustice. Attention will be drawn to the need to extend the bioethics debate to include ethical considerations regarding public health. Changes in political philosophy will also be required to reshape international power relations and improve population health. 相似文献
178.
Genetic analysis of microtubule functions in the yeast Saccharomyces cerevisiae suggests that cells manage the levels and activities of the tubulin polypeptides. These reactions may be involved in protein
folding, formation of the heterodimer, and maintenance of the appropriate balance between α- and β-tubulin. One protein involved
in these functions is Rbl2p, which forms a complex with β-tubulin. Here we describe the identification of a novel yeast gene,
RKI1, that interacts genetically with RBL2. Deletion of rki1 causes conditional defects in microtubule assembly and cell growth. Rki1p can be isolated in a complex containing Rbl2p.
The results support the existence of cellular mechanisms for regulating microtubule function through the tubulin polypeptides.
Received: 8 August 1998 / Accepted: 13 September 1998 相似文献
179.
Pruitt JR Batt DG Wacker DA Bostrom LL Booker SK McLaughlin E Houghton GC Varnes JG Christ DD Covington M Das AM Davies P Graden D Kariv I Orlovsky Y Stowell NC Vaddi KG Wadman EA Welch PK Yeleswaram S Solomon KA Newton RC Decicco CP Carter PH Ko SS 《Bioorganic & medicinal chemistry letters》2007,17(11):2992-2997
DPC168, a benzylpiperidine-substituted aryl urea CCR3 antagonist evaluated in clinical trials, was a relatively potent inhibitor of the 2D6 isoform of cytochrome P-450 (CYP2D6). Replacement of the cyclohexyl central ring with saturated heterocycles provided potent CCR3 antagonists with improved selectivity against CYP2D6. The favorable preclinical profile of DPC168 was maintained in an acetylpiperidine derivative, BMS-570520. 相似文献
180.
Nannan Yang Megan C. McDonald Peter S. Solomon Andrew W. Milgate 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2018,131(12):2765-2773