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871.
Pseudomonas aeruginosa phosphorylcholine phosphatase (PChP), the product of the PA5292 gene, is synthesized when the bacteria are grown with choline,
betaine, dimethylglycine, or carnitine. In the presence of Mg2+, PChP catalyzes the hydrolysis of both phosphorylcholine (PCh) and p-nitrophenylphosphate (p-NPP). PCh saturation curve analysis of the enzyme with or without the signal peptide indicated that the peptide was the fundamental
factor responsible for decreasing the affinity of the second site of PChP for PCh, either at pH 5.0 or pH 7.4. PChP contained
three conserved motifs characteristic of the haloacid dehalogenases superfamily. In the PChP without the signal peptide, motifs
I, II, and III correspond to the residues 31DMDNT35, 166SAA168, and K242/261GDTPDSD267, respectively. To determine the catalytic importance of the D31, D33, T35, S166, K242, D262, D265, and D267 on the enzyme
activity, site-directed mutagenesis was performed. D31, D33, D262, and D267 were identified as the more important residues
for catalysis. D265 and D267 may be involved in the stabilization of motif III, or might contribute to substrate specificity.
The substitution of T35 by S35 resulted in an enzyme with a low PChP activity, but conserves the catalytic sites involved
in the hydrolysis of PCh (Km1 0.03 mM, Km2 0.5 mM) or p-NPP (Km 2.1 mM). Mutating either S166 or K242 revealed that these residues are also important to catalyze the hydrolysis of both substrates.
The substitution of lysine by arginine or by glutamine revealed the importance of the positive charged group, either from
the amino or guanidinium groups, because K242Q was inactive, whereas K242R was a functional enzyme. 相似文献
872.
d'Avila-Levy CM Santos LO Marinho FA Dias FA Lopes AH Santos AL Branquinha MH 《Current microbiology》2006,52(6):439-444
In this study, we demonstrated that metallopeptidase inhibitors (EDTA, EGTA, and 1,10-phenanthroline) were able to arrest
Phytomonas serpens growth in distinct patterns. This parasite released exclusively metallopeptidases to the extracellular environment, whereas
in cellular extracts only cysteine peptidases were detected. In addition, an extracellular polypeptide of 60 kDa reacted in
Western blotting probed with polyclonal antibody raised against gp63 of Leishmania amazonensis. In the cellular parasite extract, this antibody recognized bands migrating at 63 and 52 kDa, which partitioned on both aqueous
and membrane-rich fractions. Flow cytometry and fluorescence microscopy analyses showed that the gp63-like molecules have
a surface location. Moreover, phospholipase C (PLC)-treated parasites reduced the number of gp63-positive cells. The anti-cross-reacting
determinant (CRD) and anti-gp63 antibodies recognized the 60-kDa band in the supernatant from PLC-treated cells, suggesting
that this protein is glycosylphosphatidylinositol-anchored to the plasma membrane. This is the first report on the presence
of gp63-like molecules in members of the Phytomonas genus. The pretreatment of the parasites with anti-gp63 antibody significantly diminished their adhesion index to explanted
salivary glands of the phytophagous insect Oncopeltus fasciatus, suggesting a potential involvement of the gp63-like molecules in the adhesive process of this plant trypanosomatid. 相似文献
873.
Growth parameters were surveyed in a sample of 296 Italian children, 6-9 years old, from Cento (Ferrara, Emilia-Romagna). The comparison with children from the same town measured in 1974-75 show changes in some parameters, suggesting an ongoing secular trend. To better understand the observed weight increase and the sex difference, we also evaluated body composition and motricity. The analysis of the present sample is a preliminary part of a longitudinal study dealing with modifications of body composition and motor capacity induced by growth. In our sample the children are growing according to the Italian reference standard. The females present weight, height and Body Mass Index (BMI) values comparable to the 50th centile, while the males present higher values of weight, skinfold thicknesses and BMI. Sex differences in the motor performance were noted. A methodological comparison of obesity assessments based on BMI and percentage of body fat (%F) shows similar conclusions but somewhat different results. 相似文献
874.
Silva GH Teles HL Zanardi LM Marx Young MC Eberlin MN Hadad R Pfenning LH Costa-Neto CM Castro-Gamboa I da Silva Bolzani V Araújo AR 《Phytochemistry》2006,67(17):1964-1969
Five cadinane sesquiterpenes derivatives were isolated by bioassay-guided fractionation from Phomopis cassiae, an endophytic fungus isolated from Cassia spectabilis. The structures of the two diastereoisomeric 3,9,12-trihydroxycalamenenes (1, 2); 3,12-dihydroxycalamenene (3); 3,12-dihydroxycadalene (4) and 3,11,12-trihydroxycadalene (5) were established on the basis of analyses of 1D and 2D NMR and HRTOFMS experiments. Antifungal activity of the isolates was evaluated against Cladosporium sphaerospermum and Cladosporium cladosporioides, revealing 5 as the most active compound. 相似文献
875.
Four metabolites, named carexanes I-L, have been isolated from the roots of Carex distachya Desf, an herbaceous plant living in the Mediterranean maquis, together with three known compounds, already isolated from the aerial part of the plant. All the compounds have been characterized on the basis of their spectroscopic properties. Carexane I derived from the lose of a proton from the C-18 carbon of an intermediate isopropyl cation. Its stereostructure has been elucidated by Mosher's method, NOESY/ROESY experiments and computational calculations. The bioactivity on seed germination and root/shoot growth of Lactuca sativa L. of all the isolated compounds is also reported. 相似文献
876.
MICROTUBULE ORGANIZATION 1 regulates structure and function of microtubule arrays during mitosis and cytokinesis in the Arabidopsis root 下载免费PDF全文
Kawamura E Himmelspach R Rashbrooke MC Whittington AT Gale KR Collings DA Wasteneys GO 《Plant physiology》2006,140(1):102-114
MICROTUBULE ORGANIZATION 1 (MOR1) is a plant member of the highly conserved MAP215/Dis1 family of microtubule-associated proteins. Prior studies with the temperature-sensitive mor1 mutants of Arabidopsis (Arabidopsis thaliana), which harbor single amino acid substitutions in an N-terminal HEAT repeat, proved that MOR1 regulates cortical microtubule organization and function. Here we demonstrate by use of live cell imaging and immunolabeling that the mor1-1 mutation generates specific defects in the microtubule arrays of dividing vegetative cells. Unlike the universal cortical microtubule disorganization in elongating mor1-1 cells, disruption of mitotic and cytokinetic microtubule arrays was not detected in all dividing cells. Nevertheless, quantitative analysis identified distinct defects in preprophase bands (PPBs), spindles, and phragmoplasts. In nearly one-half of dividing cells at the restrictive temperature of 30 degrees C, PPBs were not detected prior to spindle formation, and those that did form were often disrupted. mor1-1 spindles and phragmoplasts were short and abnormally organized and persisted for longer times than in wild-type cells. The reduced length of these arrays predicts that the component microtubule lengths are also reduced, suggesting that microtubule length is a critical determinant of spindle and phragmoplast structure, orientation, and function. Microtubule organizational defects led to aberrant chromosomal arrangements, misaligned or incomplete cell plates, and multinucleate cells. Antiserum raised against an N-terminal MOR1 sequence labeled the full length of microtubules in interphase arrays, PPBs, spindles, and phragmoplasts. Continued immunolabeling of the disorganized and short microtubules of mor1-1 at the restrictive temperature demonstrated that the mutant mor1-1(L174F) protein loses function without dissociating from microtubules, providing important insight into the mechanism by which MOR1 may regulate microtubule length. 相似文献
877.
Woll K Dressel A Sakai H Piepho HP Hochholdinger F 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2006,113(7):1305-1315
This study comprises a comprehensive gene expression analysis of the root tip specific maize gene ZmGrp3. In the first part of this paper expression of ZmGrp3 was studied in maize inbred lines. First, RNA in situ hybridization experiments confined the expression of ZmGrp3 to the columella and the epidermis of all embryonic and postembryonic root types. Second, Northern-blot analyses of the maize root initiation mutants rtcs and lrt1 revealed that the ZmGrp3 gene is not expressed prior to root initiation, thus providing a novel marker for this developmental process. Finally, a comprehensive expression profiling in 42 tissues via the Lynx MPSS system revealed almost exclusive expression of ZmGrp3 in maize roots. In the second part of this survey, ZmGrp3 expression was assayed in maize hybrids. In this context, a novel approach to quantify allele-specific contribution to gene expression in maize hybrids was developed. This assay combines RT–PCR amplification of polymorphisms between two alleles and subsequent quantification of allele-specific gene expression via a combination of didesoxyterminator assays and capillary electrophoresis. Allelic expression of the ZmGrp3 gene in six reciprocal hybrids generated from three ZmGrp3 alleles was analyzed via a new statistical mixed model approach.Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
878.
We analyze the phenomenon of spreading of a Myxococcus xanthus bacterial colony on plates coated with nutrient. The bacteria spread by gliding on the surface. In the first few hours, cell
growth is irrelevant to colony spread. In this case, bacteria spread through peninsular protrusions from the edge of the initial
colony. We analyze the diffusion through the narrowing reticulum of cells on the surface mathematically and derive formulae
for the spreading rates. On the time scale of tens of hours, effective diffusion of the bacteria, combined with cell division
and growth, causes a constant linear increase in the colony's radius. Mathematical analysis and numerical solution of reaction-diffusion
equations describing the bacterial and nutrient dynamics demonstrate that, in this regime, the spreading rate is proportional
to the square root of both the effective diffusion coefficient and the nutrient concentration. The model predictions agree
with the data on spreading rate dependence on the type of gliding motility. 相似文献
879.
880.
mRNA-based parallel detection of active methanotroph populations by use of a diagnostic microarray 总被引:1,自引:0,他引:1
Bodrossy L Stralis-Pavese N Konrad-Köszler M Weilharter A Reichenauer TG Schöfer D Sessitsch A 《Applied and environmental microbiology》2006,72(2):1672-1676
A method was developed for the mRNA-based application of microbial diagnostic microarrays to detect active microbial populations. DNA- and mRNA-based analyses of environmental samples were compared and confirmed via quantitative PCR. Results indicated that mRNA-based microarray analyses may provide additional information on the composition and functioning of microbial communities. 相似文献