bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification of Natural Rubber and Characterization of Rubber Biosynthetic Activity in Fig Tree
Authors: Kang Hunseung , Kang Min Young , Han Kyung-Hwan 
Published: July 2002

Abstract
Natural rubber was extracted from the fig tree (Ficus carica) cultivated in Korea as part of a survey of rubber producing plants. Fourier transform infrared and 13C nuclear magnetic resonance analysis of samples prepared by successive extraction with acetone and benzene confirmed that the benzene-soluble residues are natural rubber, cis-1,4-polyisoprene. The rubber content in the latex of fig tree was about 4%, whereas the rubber content in the bark, leaf, and fruit was 0.3%, 0.1%, and 0.1%, respectively. Gel-permeation chromatography revealed that the molecular size of the natural rubber from fig tree is about 190 kD. Similar to rubber tree (Hevea brasiliensis) and guayule (Parthenium argentatum Gray), rubber biosynthesis in fig tree is tightly associated with rubber particles. The rubber transferase in rubber particles exhibited a higher affinity for farnesyl pyrophosphate than for isopentenyl pyrophosphate, with apparentK m values of 2.8 and 228 μm, respectively. Examination of latex serum from fig tree by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed major proteins of 25 and 48 kD in size, and several proteins with molecular mass below 20 and above 100 kD. Partial N-terminal amino acid sequencing and immunochemical analyses revealed that the 25- and 48-kD proteins were novel and not related to any other suggested rubber transferases. The effect of EDTA and Mg2+ ion on in vitro rubber biosynthesis in fig tree and rubber tree suggested that divalent metal ion present in the latex serum is an important factor in determining the different rubber biosynthetic activities in fig tree and rubber tree.
Nod Factors and Chitooligomers Elicit an Increase in Cytosolic Calcium in Aequorin-Expressing Soybean Cells
Authors: Müller Joachim , Staehelin Christian , Xie Zhi-Ping , Neuhaus-Url Gabriele , Boller Thomas 
Published: July 2002

Abstract
Rhizobial Nod factors (NFs) function as nodulation signals that trigger symbiotic responses of leguminous host plants. NFs consist of a chitin oligomer backbone carrying a fatty acid at the non-reducing end. Depending on the rhizobial strain, NFs carry additional substituents, which may determine host specificity. Transgenic suspension-cultured soybean (Glycine max [L.] Merr.) cells expressing aequorin have been used to record cytosolic [Ca2+] changes upon treatment with purified NFs and chitin fragments. Both compounds elicited an increase of cytosolic [Ca2+] at nanomolar concentrations. The shape and amplitude of cytosolic [Ca2+] changes was similar to the response elicited by un-derivatized chitin oligomers. Cells challenged first with NFs did not respond to a subsequent treatment with chitin oligomers and vice versa. Dose-response experiments showed that un-derivatized chitin oligomers were more active compared with NFs. The capacity of NFs to elicit the calcium response depended on their structure. The presence of reducing end substituents in methylfucosylated NFs fromRhizobium sp. NGR234 and the O-acetyl group at the non-reducing end in NFs from Sinorhizobium meliloti attenuated the activity to cause the calcium changes. The sulfate group in NFs from Rhizobium tropici did not affect the elicitor activity. Pentameric S. meliloti NFs were more active than tetrameric molecules, whereas trimeric or dimeric degradation products were inactive. Substituents in NFs may have the function to avoid stimulation of defense reactions mediated by the perception system for chitin oligomers.
Expression and Stress-Dependent Induction of Potassium Channel Transcripts in the Common Ice Plant
Authors: Su Hua , Golldack Dortje , Katsuhara Maki , Zhao Chengsong , Bohnert Hans J. 
Published: July 2002

Abstract
We have characterized transcripts for three potassium channel homologs in the AKT/KAT subfamily (Shaker type) from the common ice plant (Mesembryanthemum crystallinum), with a focus on their expression during salt stress (up to 500 mm NaCl).Mkt1 and 2, Arabidopsis AKT homologs, andKmt1, a KAT homolog, are members of small gene families with two to three isoforms each. Mkt1 is root specific;Mkt2 is found in leaves, flowers, and seed capsules; andKmt1 is expressed in leaves and seed capsules.Mkt1 is present in all cells of the root, and in leaves a highly conserved isoform is detected present in all cells with highest abundance in the vasculature. MKT1 for which antibodies were made is localized to the plasma membrane. Following salt stress, MKT1 (transcripts and protein) is drastically down-regulated,Mkt2 transcripts do not change significantly, andKmt1 is strongly and transiently (maximum at 6 h) up-regulated in leaves and stems. The detection and stress-dependent behavior of abundant transcripts representing subfamilies of potassium channels provides information about tissue specificity and the complex regulation of genes encoding potassium uptake systems in a halophytic plant.
Hydrogen Peroxide Mediates the Induction of Chloroplastic Ndh Complex under Photooxidative Stress in Barley
Authors: Casano Leonardo M. , Martı́n Mercedes , Sabater Bartolomé 
Published: July 2002

Abstract
Chloroplast-encoded NDH polypeptides (components of the plastid Ndh complex) and the NADH dehydrogenase activity of the Ndh complex (NADH-DH) increased under photooxidative stress. The possible involvement of H2O2-mediated signaling in the photooxidative induction of chloroplastic ndh genes was thoroughly studied. We have analyzed the changes in the NADH-DH and steady-state levels of NDH-F polypeptide and ndhB andndhF transcripts in barley (Hordeum vulgare cv Hassan) leaves. Subapical leaf segments were incubated in growing light (GL), photooxidative light (PhL), GL and H2O2 (GL + H2O2), or PhL and 50 nm paraquat in the incubation medium. Treatments with H2O2 under GL mimicked the photooxidative stimulus, causing a dose-dependent increase of NADH-DH and NDH-F polypeptide. The kinetic of Ndh complex induction was further studied in leaves pre-incubated with or without the H2O2-scavenger dimethyltiourea. NADH-DH and NDH-F polypeptide rapidly increased up to 16 h in PhL, GL+ H2O2, and, at higher rate, in PhL and paraquat. The observed increases of NADH-DH and NDH-F after 4 h in PhL and GL + H2O2 were not accompanied by significant changes in ndhB and ndhF transcripts. However, at 16-h incubations NADH-DH and NDH-F changes closely correlated with higher ndhB and ndhFtranscript levels. All these effects were prevented by dimethylthiourea. It is proposed that the induction of chloroplasticndh genes under photooxidative stress is mediated by H2O2 through mechanisms that involve a rapid translation of pre-existing transcripts and the increase of thendh transcript levels.
Simultaneous Down-Regulation of Caffeic/5-Hydroxy Ferulic Acid-O-Methyltransferase I and Cinnamoyl-Coenzyme A Reductase in the Progeny from a Cross between Tobacco Lines Homozygous for Each Transgene. Consequences for Plant Development and Lignin Synthesis
Authors: Pinçon Gaelle , Chabannes Matthieu , Lapierre Catherine , Pollet Brigitte , Ruel Katia , Joseleau Jean-Paul , Boudet Alain M. , Legrand Michel 
Published: July 2002

Abstract
Inhibition of specific lignin biosynthetic steps by antisense strategy has previously been shown to alter lignin content and/or structure. In this work, homozygous tobacco (Nicotiana tabacum) lines transformed with cinnamoyl-coenzyme A reductase (CCR) or caffeic acid/5-hydroxy ferulic acid-O-methyltransferase I (COMT I) antisense sequences have been crossed and enzyme activities, lignin synthesis, and cell wall structure of the progeny have been analyzed. In single transformed parents, CCR inhibition did not affect COMT I expression, whereas marked increases in CCR activity were observed in COMT I antisense plants, suggesting potential cross talk between some genes of the pathway. In the progeny, both CCR and COMT I activities were shown to be markedly decreased due to the simultaneous repression of the two genes. In these double transformants, the lignin profiles were dependent on the relative extent of down-regulation of each individual enzyme. For the siblings issued from a strongly repressed antisense CCR parent, the lignin patterns mimicked the patterns obtained in single transformants with a reduced CCR activity. In contrast, the specific lignin profile of COMT I repression could not be detected in double transformed siblings. By transmission electron microscopy some cell wall loosening was detected in the antisense CCR parent but not in the antisense COMT I parent. In double transformants, immunolabeling of non-condensed guaiacyl-syringyl units was weaker and revealed changes in epitope distribution that specifically affected vessels. Our results more widely highlight the impact of culture conditions on phenotypes and gene expression of transformed plants.
Molecular Characterization of At5PTase1, an Inositol Phosphatase Capable of Terminating Inositol Trisphosphate Signaling,
Authors: Berdy Sara E. , Kudla Joerg , Gruissem Wilhelm , Gillaspy Glenda E. 
Published: July 2002

Abstract
The inositol triphosphate (IP3)-signaling pathway has been associated with several developmental and physiological processes in plants, but we currently know little about the regulation of this pathway. Inositol 5′ phosphatases (5PTases) are enzymes that remove a 5′ phosphate from several potential second messengers, including IP3. In catalyzing the removal of a 5′ phosphate from second messenger substrates, 5PTases can act to terminate signal transduction events. We describe the molecular analysis of At5PTase1, a 5PTase gene from Arabidopsis. When expressed transiently in Arabidopsis leaf tissue or ectopically in transgenic plants, At5PTase1 allowed for the increased hydrolysis of I(1,4,5)P3 and I(1,3,4,5)P4 substrates. At5PTase1 did not hydrolyze I(1)P, I(1,4)P2, or PI(4,5)P2 substrates. This substrate specificity was similar to that of the human Type I 5PTase. We identified 14 other potential At5PTase genes and constructed an unrooted phylogenetic tree containing putative Arabidopsis, human, and yeast 5PTase proteins. This analysis indicated that the Arabidopsis 5PTases were grouped in two separate branches of the tree. The multiplicity of At5PTases indicates that these enzymes may have different substrate specificities and play different roles in signal termination in Arabidopsis.
Structure determination of two intercalated compounds VOPO4·(CH2)4O and VOPO4·OH—(CH2)2—O—(CH2)2—OH; synchrotron powder diffraction and molecular modelling
Authors: Goubitz Kees , Čapková Pavla , Melánová Klára , Molleman Wim , Schenk Henk 
Published: July 2002

The crystal structures of two intercalated compounds have been determined using a combination of synchrotron powder diffraction and molecular mechanics simulations: (1) vanadyl phosphate intercalated with tetrahydrofuran, VOPO4·(CH2)4O, and (2) vanadyl phosphate intercalated with diethylene glycol, VOPO4·HO(CH2)2O(CH2)2OH. Both intercalates preserve the tetragonal space group P4/n, as found in the host structure VOPO4·2H2O. (1): a = 6.208, c = 8.930 Å, Z = 2, Dx
= 2.51 g cm−3; (2): a = 6.223, c = 11.417 Å, Z = 2, Dx
= 2.66 g cm−3. Both intercalates exhibit the same type of orientational disorder in the arrangement of guest molecules, as observed in the same host compound intercalated with water. These two intercalates also exhibit, rather surprisingly, perfect ordering in layer stacking without the displacement disorder, characteristic of many intercalated layered structures. Thanks to this regularity in the arrangement of guests and layers, synchrotron powder diffraction could be used in the present structure determination. The present results also enabled the analysis of the effect of geometrical parameters characterizing the mutual host–guest complementarity and the effect of host–guest and guest–guest interaction on the crystal packing of intercalates.
Crystallization and preliminary X-ray analysis of polyamine oxidase from Zea mays L.
Authors: Binda Claudia , Coda Alessandro , Angelini Riccardo , Federico Rodolfo , Ascenzi Paolo , Mattevi Andrea 
Published: July 2002

Polyamine oxidase catalyses the oxidation of the secondary amino group of spermine, spermidine and their acetyl derivatives. The enzyme plays an important role in the regulation of polyamine intracellular concentration and is a member of the family of flavin-containing amine oxidases. Crystals of maize polyamine oxidase have been grown by the hanging-drop vapour-diffusion technique. The crystals are in hexagonal space group P6122 (or P6522) with cell dimensions a = b = 184.6, c = 280.9 Å. A native data set has been collected to 2.7 Å resolution at a synchrotron radiation source.
Crystallization and preliminary crystallographic analysis of the snake muscle fructose 1,6-bisphosphatase
Authors: Zhu D.-W. , Xu G.-J. , Rehse P. H. , Azzi A. , Zhao F.-K. , Lin S.-X. 
Published: July 2002

The snake muscle fructose 1,6-bisphosphatase, a typical allosteric enzyme which plays important roles in gluconeogenesis, was crystallized in the presence of polyethylene glycol 3350 and magnesium chloride at pH 8.5. The crystals diffract to 2.3 Å on a rotating-anode X-ray source. The space group was determined to be either P3121 or its enantiomorph P3221, with unit-cell parameters a = b = 83.7, c = 202.41 Å, α = β = 90 and γ = 120°. There are two subunits in the asymmetric unit. Preliminary molecular-replacement studies indicate that the first enantiomorph is the correct one.
Crystallization and preliminary X-ray analysis of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (tyrosine inhibitable) from Saccharomyces cerevisiae
Authors: Schneider Thomas R. , Hartmann Markus , Braus Gerhard H. 
Published: July 2002

3-Deoxy-D-arabino-heptulosonate-7-phosphate synthase (E.C. 4.1.2.15) catalyzes the first step in the biosynthesis of aromatic amino acids: the condensation of phophoenolpyruvate and erythrose 4-phosphate to 3-deoxy-D-arabino-heptulosonate-7-phosphate. Diffraction-quality crystals of the tyrosine-inhibitable form of the enzyme from Saccharomyces cerevisiae have been obtained by the hanging-drop vapour-diffusion method in the presence of polyethylene glycol. The crystals belong to the triclinic space group P1, with unit-cell parameters a = 81.5, b = 94.0, c = 104.6 Å, α = 65.5, β = 85.2, γ = 75.0°, and can be flash-cooled using glycerol as a cryoprotectant. A data set to 2.3 Å has been collected at 120 K.
Purification, crystallization and preliminary X-ray analysis of catabolic ornithine carbamoyltransferase from Pseudomonas aeruginosa
Authors: Sainz G. , Vicat J. , Kahn R. , Tricot C. , Stalon V. , Dideberg O. 
Published: July 2002

The catabolic ornithine carbamoyltransferase (OTCase) from Pseudomonas aeruginosa exhibits allosteric behaviour, with two conformational states of the molecule: an active R form and an inactive T form. The enzyme is a dodecamer with a molecular mass of 455700 Da. Three crystal forms have been obtained. Crystals of allosteric state T are rhombohedral, belonging to the R3 space group, with hexagonal unit-cell parameters a = b = 180.6, c = 122.0 Å. They diffract to a resolution of 4.5 Å. Two crystal forms for allosteric state R have been obtained, with hexagonal and cubic symmetries. Hexagonal crystals, which diffract to a resolution of 3.4 Å, belong to the space group P63 with unit-cell parameters a = b = 140.8, c = 145.6 Å. The cubic crystals belong to space group I23, with unit-cell parameter a = 134.32 Å and diffract to a resolution better than 2.5 Å. In all crystal forms, the dodecamer exhibits a 23 point-group symmetry.
Station 16.3: a High-Resolution Single-Crystal Diffraction Facility at the SRS, Daresbury
Authors: Collins S. P. , Cernik R. J. , Fell B. , Tang C. C. , Harris N. W. , Miller M. C. , Oszlanyi G. 
Published: July 2002

SRS station 16.3 is now a fully scheduled user facility for high-resolution and high-energy single-crystal X-ray diffraction. It is based on a large three-axis diffractometer, designed and constructed at Daresbury for a wide range of physics and materials science applications. Served by wiggler 16 (a 6 T superconducting wavelength-shifter), the station has access to a broad spectrum of photon energies, extending to over 50 keV, and is designed for simple polarization-state tuning by motorized height adjustment of all optical components. This paper outlines the key design features and some of the science projects carried out during the first year of operation.
Crystal structure of threonine synthase from Arabidopsis thaliana
Authors: Thomazeau Karine , Curien Gilles , Dumas Renaud , Biou Valérie 
Published: July 2002

AbstractThreonine synthase (TS) is a PLP‐dependent enzyme that catalyzes the last reaction in the synthesis of threonine from aspartate. In plants, the methionine pathway shares the same substrate, O‐phospho‐L‐homoserine (OPH), and TS is activated by S‐adenosyl‐methionine (SAM), a downstream product of methionine synthesis. This positive allosteric effect triggered by the product of another pathway is specific to plants. The crystal structure of Arabidopsis thaliana apo threonine synthase was solved at 2.25 Å resolution from triclinic crystals using MAD data from the selenomethionated protein. The structure reveals a four‐domain dimer with a two‐stranded β‐sheet arm protruding from one monomer onto the other. This domain swap could form a lever through which the allosteric effect is transmitted. The N‐terminal domain (domain 1) has a unique fold and is partially disordered, whereas the structural core (domains 2 and 3) shares the functional domain of PLP enzymes of the same family. It also has similarities with SAM‐dependent methyltransferases. Structure comparisons allowed us to propose potential sites for pyridoxal‐phosphate and SAM binding on TS; they are close to regions that are disordered in the absence of these molecules.
Nested allosteric interactions in the cytoplasmic chaperonin containing TCP‐1
Authors: Kafri Galit , Willison Keith R. , Horovitz Amnon 
Published: July 2002

AbstractInitial rates of ATP hydrolysis by the chaperonin containing TCP‐1 (CCT) from bovine testis were measured as a function of ATP concentration. Two allosteric transitions are observed: one at relatively low concentrations of ATP (<100 μM) and the second at higher concentrations of ATP. The data suggest that CCT has positive intra‐ring cooperativity and negative inter‐ring cooperativity in ATP hydrolysis, with respect to ATP, as previously observed in the case of GroEL. It is shown that the relatively weak positive intra‐ring cooperativity found in the case of CCT may be due to heterogeneity in its subunit composition. Our results suggest that nested allosteric behavior may be common to chaperone double‐ring systems.
Evaluation of Nitrofurantoin Combination Therapy of Metronidazole-Sensitive and -Resistant
Helicobacter pylori
Infections in Mice
Authors: Jenks Peter J. , Ferrero Richard L. , Tankovic Jacques , Thiberge Jean-Michel , Labigne Agnès 
Published: July 2002

ABSTRACT

The main objectives of this study were to determine whether the nitroreductase enzyme encoded by the
rdxA
gene of
Helicobacter pylori
was responsible for reductive activation of nitrofurantoin and whether a triple-therapy regimen with nitrofurantoin was able to eradicate metronidazole-sensitive and -resistant
H. pylori
infections from mice. The susceptibilities to nitrofurantoin of parent and isogenic
rdxA
mutant strains (three pairs), as well as a series of matched metronidazole-sensitive and -resistant strains isolated from mice (30) and patients (20), were assessed by agar dilution determination of the MIC. Groups of mice colonized with the metronidazole-sensitive
H. pylori
SS1 strain or a metronidazole-resistant
rdxA
SS1 mutant were treated with either metronidazole or nitrofurantoin as part of a triple-therapy regimen. One month after the completion of treatment the mice were sacrificed and their stomachs were cultured for
H. pylori
. The nitrofurantoin MICs for all strains tested were between 0.5 and 4.0 μg/ml. There was no significant difference between the susceptibility to nitrofurantoin of the parental strains and those of respective
rdxA
mutants or between those of matched metronidazole-sensitive and -resistant
H. pylori
isolates. The regimen with metronidazole eradicated infection from all eight SS1-infected mice and from one of eight mice inoculated with the
rdxA
mutant (
P
≤ 0.001). The regimen with nitrofurantoin failed to eradicate infection from any of the six SS1-infected mice (
P
≤ 0.001) and cleared infection from one of seven mice inoculated with the
rdxA
mutant. These results demonstrate that, despite the good in vitro activity of nitrofurantoin against
H. pylori
and the lack of cross-resistance between metronidazole and nitrofurantoin, eradication regimens involving nitrofurantoin are unable to eradicate either metronidazole-sensitive or -resistant
H. pylori
infections from mice.
In Vitro Activities of Ravuconazole (BMS-207147) against 541 Clinical Isolates of
Cryptococcus neoformans
Authors: Yamazumi T. , Pfaller M. A. , Messer S. A. , Houston A. , Hollis R. J. , Jones R. N. 
Published: July 2002

ABSTRACT

The in vitro activities of the new triazole, ravuconazole (BMS-207147), were compared to those of fluconazole and itraconazole against 541 clinical isolates of
Cryptococcus neoformans
. Isolates were obtained from cerebrospinal fluid (396), blood (116), and miscellaneous clinical specimens (29). Overall, ravuconazole (MIC at which 90% of the isolates are inhibited [MIC
90
], 0.25 μg/ml) was more active than either itraconazole (MIC
90
, 0.5 μg/ml) or fluconazole (MIC
90
, 8 μg/ml). Among the isolates inhibited by ≥16 μg of fluconazole/ml, 90.2% were inhibited by ≤1 μg of ravuconazole/ml. On the basis of our findings and the favorable pharmacokinetic properties of ravuconazole, we suggest that ravuconazole may be useful for the treatment of infectious diseases due to
C. neoformans
and that further clinical studies to confirm these promising in vitro results are warranted.
Reversion of the Glycopeptide Resistance Phenotype in
Staphylococcus aureus
Clinical Isolates
Authors: Boyle-Vavra Susan , Berke Sarah K. , Lee Jean C. , Daum Robert S. 
Published: July 2002

ABSTRACT

The recent identification of glycopeptide intermediate-resistant
Staphylococcus aureus
(GISA) clinical isolates has provided an opportunity to assess the stability of the glycopeptide resistance phenotype by nonselective serial passage and to evaluate reversion-associated cell surface changes. Three GISA isolates from the United States (MIC of vancomycin = 8 μg/ml) and two from Japan (MICs of vancomycin = 8 and 2 μg/ml) were passaged daily on nutrient agar with or without vancomycin supplementation. After 15 days of passage on nonselective medium, vancomycin- and teicoplanin-susceptible revertants were obtained from each GISA isolate as determined by broth dilution MIC. Revertant isolates were compared with parent isolates for changes in vancomycin heteroresistance, capsule production, hemolysis phenotype, coagulase activity, and lysostaphin susceptibility. Several revertants lost the subpopulations with intermediate vancomycin resistance, whereas two revertants maintained them. Furthermore, although all of the parent GISA isolates produced capsule type 5 (CP5), all but one revertant tested no longer produced CP5. In contrast, passage on medium containing vancomycin yielded isolates that were still intermediately resistant to vancomycin, had no decrease in the MIC of teicoplanin, and produced detectable CP5. No consistent changes in the revertants in hemolysis phenotype, lysostaphin susceptibility, or coagulase activities were discerned. These data indicate that the vancomycin resistance phenotype is unstable in clinical GISA isolates. Reversion of the vancomycin resistance phenotype might explain the difficulty in isolating vancomycin-resistant clinical isolates from the blood of patients who fail vancomycin therapy and, possibly, may account for some of the difficulties in identifying GISA isolates in the clinical laboratory.