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At least 955 records · Page 53Linked to original sources
PubMed2006

The Rhizobium leguminosarum biovar trifolii ANU794 induces novel developmental responses on the subterranean clover cultivar Woogenellup.

The clover-nodulating Rhizobium leguminosarum bv. trifolii ANU794 initiates normal root-nodule development with abnormally low efficiency on the Trifolium subterraneum cv. Woogenellup. The cellular and developmental responses of Woogenellup roots to the site- and dose-defined inoculation of green fluorescent protein (gfp)-labeled cells of ANU843 (nodulation proficient) and ANU794 was investigated using light, fluorescence, and confocal microscopy. Strain ANU794-gfp induced three primordia types and four developmental responses at the inoculation site: true or aberrant nodules (on 5 and 25% of plants, respectively), hybrid structures (20% of plants), or lateral roots (50% of plants). The novel hybrid structures possessed nodule and lateral root-like features and unusual vascular patterning. Strain ANU794-gfp induces lateral root formation by stimulating pericycle cell divisions at all nearby protoxylem poles. Only true nodules induced by ANU794-gfp contained intracellular bacteria. In contrast, strain ANU843-gfp induced nodules only and lateral root formation was suppressed at spot inoculation sites. Primordium types were distinguishable by the emission spectrum characteristics of phenolic UV-absorbing and fluorescent compounds that accumulate in primordium cells. Hybrid primordia contained (at least) two fluorescent cell populations, suggesting that they are chimeric. The results suggest that ANU794 may produce both nodule- and lateral root-generating signals simultaneously.

Chromatography, High Pressure Liquid↗
PubMed2005

Evidence of the involvement of plant ligno-cellulosic structure in the sequestration of Pb: an X-ray spectroscopy-based analysis.

European walnut (Juglans regia) plants were grown in pots, on peat soil contaminated with lead (Pb), for four years. European walnut was chosen because it grows in Mediterranean climates, it yields a high biomass, and a fine quality wood. In the above ground parts Pb concentration was 1000 times lower than in roots: in 50 g roots there was 450 mg of Pb. Microanalysis of roots found in periderm more than 50% of the total root Pb. Pb L(III) EXAFS spectroscopy was performed on: root powder from Pb-exposed plants, Pb-impregnated cellulose and lignin. Comparison of plant material with lignin and cellulose helped to envisage a plant disposal strategy for Pb. This may consist in establishing links with large organic molecules, which are abundant constituents of cell walls. EXAFS spectroscopy evidenced the presence of Pb-O bindings within the ligno-cellulosic structure in roots. Lead was scantly conveyed to the shoots, giving to walnut plants an added asset in Pb phytostabilization.

Calcium↗
PubMed2000

Cytochrome P4501A1-inhibitory action of antimutagenic anthraquinones in medicinal plants and the structure-activity relationship.

We have earlier found that flavones and flavonols in vegetables specifically inhibited one of the carcinogenesis-related enzymes, cytochrome P450 (CYP) 1A1, and subsequently suppressed the mutagenicity of food-derived carcinogens. In this study, we explored other candidates for the enzyme inhibitor in Chinese medicinal plants. Some of them were antimutagenic toward 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2). For example, Rheum officinale contained large amounts of anthraquinones as the active compounds, 3.4 mg of emodin, 2.1 mg of chrysophanol and 1.8 mg of rhein in 10 g of dry matter. Anthraquinones showed similar IC50 values for antimutagenicity against Trp-P-2 to those for inhibition of the N-hydroxylation activity of CYP1A1 toward Trp-P-2, indicating that the antimutagenicity was attributable to CYP inhibition. The structure-activity relationships were then examined with 14 commercial chemicals, and it was found that the interaction with an enzyme required three rings and an oxygen group in the side ring. This characteristic is similar to that of flavones and flavonols.

Anthraquinones↗
PubMed1998

Higher plants light harvesting proteins. Structure and function as revealed by mutation analysis of either protein or chromophore moieties.

Mutation analysis of higher plants light harvesting proteins has been prevented for a long time by the lack of a suitable expression system providing chromophores essential for the folding of these membrane-intrinsic pigment-protein complexes. Early work on in vitro reconstitution of the major light harvesting complex of photosystem II (LHCII) indicated an alternative way to mutation analysis of these proteins. A new procedure for in vitro refolding of the four light harvesting complexes of photosystem II, namely CP24, CP29, CP26 and LHCII yields recombinant pigment-proteins indistinguishable from the native proteins isolated from leaves. This method allows both the performing of single point mutations on protein sequence and the exchange of the chromophores bound to the protein scaffold. We review here recent results obtained by this method on the pigment-binding properties, on the chlorophyll-binding residues, on the identification of proton-binding sites and on the role of xanthophylls in the regulation of light harvesting function.

Amino Acid Sequence↗
PubMed1988

Ribosome-inhibiting proteins, retroviral reverse transcriptases, and RNase H share common structural elements.

Plant ribosome-inhibiting proteins are shown to be homologous at the domain level to RNase H from Escherichia coli and to two regions of the pol gene product of retroviral reverse transcriptases. One of these regions carries the viral integrase or int function, while the other has previously been suggested to contain the viral RNase H exo activity. Several residues conserved among the ribosome inhibitors, E. coli RNase H, and the integrase proteins are seen to occupy a prominent cleft in the tertiary structure of the ribosome inhibitor ricin, suggesting roles in binding or catalysis. It is likely that these homologous sequences represent modern derivatives of an ancient protein-folding unit capable of nucleic acid binding and modification which has been incorporated into a variety of enzyme functions.

Amino Acid Sequence↗
PubMed2002

TonB-dependent receptors-structural perspectives.

Plants, bacteria, fungi, and yeast utilize organic iron chelators (siderophores) to establish commensal and pathogenic relationships with hosts and to survive as free-living organisms. In Gram-negative bacteria, transport of siderophores into the periplasm is mediated by TonB-dependent receptors. A complex of three membrane-spanning proteins TonB, ExbB and ExbD couples the chemiosmotic potential of the cytoplasmic membrane with siderophore uptake across the outer membrane. The crystallographic structures of two TonB-dependent receptors (FhuA and FepA) have recently been determined. These outer membrane transporters show a novel fold consisting of two domains. A 22-stranded antiparallel beta-barrel traverses the outer membrane and adjacent beta-strands are connected by extracellular loops and periplasmic turns. Located inside the beta-barrel is the plug domain, composed primarily of a mixed four-stranded beta-sheet and a series of interspersed alpha-helices. Siderophore binding induces distinct local and allosteric transitions that establish the structural basis of signal transduction across the outer membrane and suggest a transport mechanism.

ATP-Binding Cassette Transporters↗
PubMed2006

Triterpenoid saponins from the fruits of Caryocar glabrum.

Twenty-one new triterpenoid saponins, named caryocarosides (1-21), glycosides of 2beta-hydroxyoleanolic acid, hederagenin, bayogenin, and gypsogenic acid, have been isolated from the fruits of Caryocar glabrum along with nine known triterpenoid saponins (22-30) that are described for the first time from a plant in the Caryocaraceae. Their structures were established by 1D and 2D NMR techniques ((13)C, COSY, TOCSY, HSQC, HMBC, and ROESY experiments), ESIMS, and acid hydrolysis. The isolated compounds could be classified into two series: glucosides (1-8, 22, 27, and 30) derived from the 3-O-monoglucoside and glucuronides (9-21, 23-26, 28, and 29) derived from the 3-O-monoglucuronide. In 22 of the saponins (1-8, 12-22, and 24-26), a galactose moiety was linked to C-3 of a glucuronic acid or a glucose moiety. The galactose was substituted in position 3 by a second galactose unit (6, 7, 20, and 21) or by a xylose unit (8). Seven saponins (4, 5, 16-19, and 26) were found to be bidesmosides with one glucose unit linked to C-28 of the aglycon. The hemolytic activity of the major saponins (2, 3, 5, 12-15, 17, 24, and 28) was measured on sheep erythrocytes in order to establish structure-activity relationships based on the type of sugar attached to the aglycon and on the structure of this aglycon.

Animals↗
PubMed2001

Detection of chromosomes tagged with green fluorescent protein in live Arabidopsis thaliana plants.

BACKGROUND: Structural and dynamic studies of chromosomes tagged with green fluorescent protein (GFP) in yeast and cultured animal cells have revealed some surprises. Although this technology can be very powerful, only a few studies using this approach with developed multicellular systems have been reported for the study of chromatin behavior in situ. RESULTS: We established vectors and conditions to visualize tagged loci stably inserted in the Arabidopsis genome via GFP fused to a bacterial DNA-binding protein. Using this system, three-dimensional coordinates for tagged loci within nuclei from cells of a live plant can be directly determined with concomitant visualization of the position of the nucleolus. Chromosome polyploidization in epidermal cells at the elongation zone of the root in transgenic plants can be visualized in situ using this technique. CONCLUSION: We have established that GFP fusion with DNA-binding proteins can be used in conjunction with concatameric binding-site arrays to track genomic loci in living Arabidopsis plants. It should now be feasible to study the mechanisms of organization and dynamics of chromatin in specific cell types during various times of plant development, taking advantage of the well developed genetic systems and resources available for Arabidopsis.

Arabidopsis↗
PubMed2002

Incorporating soil structure and root distribution into plant uptake models for radionuclides: toward a more physically based transfer model.

Most biosphere and contamination assessment models are based on uniform soil conditions, since single coefficients are used to describe the transfer of contaminants to the plant. Indeed, physical and chemical characteristics and root distribution are highly variable in the soil profile. These parameters have to be considered in the formulation of a more realistic soil-plant transfer model for naturally structured soils. The impact of monolith soil structure (repacked and structured) on Zn and Mn uptake by wheat was studied in a controlled tracer application (dye and radioactive) experiment. We used Brilliant Blue and Sulforhodamine B to dye flow lines and 65Zn and 54Mn to trace soil distribution and plant uptake of surface-applied particle-reactive contaminants. Spatial variation of the soil water content during irrigation and plant growth informs indirectly about tracer and root location in the soil profile. In the structured monolith, a till pan at a depth of 30 cm limited vertical water flow and root penetration into deeper soil layers and restricted tracers to the upper third of the monolith. In the repacked monolith, roots were observed at all depths and fingering flow allowed for the fast appearance of all tracers in the outflow. These differences between the two monoliths are reflected by significantly higher 54Mn and 65Zn uptake in wheat grown on the structured monolith. The higher uptake of Mn can be modelled on the basis of radionuclide and root distribution as a function of depth and using a combination of preferential flow and rooting. The considerably higher uptake of Zn requires transfer factors which account for variable biochemical uptake as a function of location.

Forecasting↗
PubMed2005

Structure-function relationships in plant phenylpropanoid biosynthesis.

Plants, as sessile organisms, evolve and exploit metabolic systems to create a rich repertoire of complex natural products that hold adaptive significance for their survival in challenging ecological niches on earth. As an experimental tool set, structural biology provides a high-resolution means to uncover detailed information about the structure-function relationships of metabolic enzymes at the atomic level. Together with genomic and biochemical approaches and an appreciation of molecular evolution, structural enzymology holds great promise for addressing a number of questions relating to secondary or, more appropriately, specialized metabolism. Why is secondary metabolism so adaptable? How are reactivity, regio-chemistry and stereo-chemistry steered during the multi-step conversion of substrates into products? What are the vestigial structural and mechanistic traits that remain in biosynthetic enzymes during the diversification of substrate and product selectivity? What does the catalytic landscape look like as an enzyme family traverses all possible lineages en route to the acquisition of new substrate and/or product specificities? And how can one rationally engineer biosynthesis using the unique perspectives of evolution and structural biology to create novel chemicals for human use?

Biological Evolution↗
PubMed1981

Primary structure of the hydrophobic plant protein crambin.

Crambin, a hydrophobic plant seed protein, consists of a single chain of 46 amino acids with a calculated molecular weight of 4720. The primary structure was determined by using solid-phase sequencing techniques and was confirmed through X-ray crystallographic analysis of the protein at 1.5-A resolution [Hendrickson, W. A., & Teeter, M. M. (1981) Nature (London) 290, 107-112]. High-performance liquid chromatographic separation of the proteolytic fragments from crambin led to the identification of two sites of microheterogeneity. The three disulfide bonds were located at positions 3-40, 4-32, and 16-26 from the crystallographic data. Comparison of the primary structure with known sequences revealed that crambin is homologous with the plant toxins purothionin and viscotoxin. Methods to estimate protein secondary structure were applied and found to predict all of crambin's structure except its amphiphilic helix.

Amino Acid Sequence↗
PubMed1998

Structure and function of proteins controlling strain-specific pathogen resistance in plants.

Recently recognised structural and amino acid sequence similarities between plant disease resistance (R) proteins and animal proteins such as Apaf-1 and CED-4 are providing conceptual models for resistance protein function. Data from extensive DNA sequencing of resistance gene families are indicating that the leucine-rich repeat motif is an important determinant of gene-for-gene specificity and that intergenic DNA sequence exchange is a major contributor to R gene diversity.

Apoptosis↗
PubMed2004

[Structure and function of plant C2H2 zinc finger protein].

Zinc finger protein is one of the important transcription factors with zinc finger domain that regulates gene expression in the eukaryotic organisms mainly by specifically interacting with target DNA sequence(cis-acting element). It could be divided into several types of zinc finger proteins, such as C2H2, C2HC, C2C2, C2HCC2C2, C2C2C2C2 etc, based on numbers and positions of Cys and His residues. Of these, C2H2 type zinc finger protein is the most clearly identified zinc finger transcription factor, with the wide existence in human, animals and plants. The characterized plant C2H2 zinc finger proteins are mainly involved in plant growth and development and the responses to environmental stresses. Up to now, more than 50 C2H2 zinc finger proteins have been reported in plants including petunia, Arabidopsis, wheat and rice, and most of them have the plant-specific QALGGH motif in zinc finger domain. This paper briefly introduces the structure, recognition of target-DNA sequence and functions involved in development or environmental stresses of plant C2H2 zinc finger proteins.

Amino Acid Sequence↗
PubMed2005

The controversial telomeres of lily plants.

The molecular structure of the exceptional telomeres of six plant species belonging to the order Asparagales and two species of the order Liliales was analyzed using Southern blot and fluorescence in situ hybridization. Three different situations were found, namely: i) In the two Liliales species, Tulipa australis (Liliaceae) and Merendera montana (Colchicaceae), the chromosome ends display hybridization signals with oligonucleotides resembling telomere repeats of both plants (TTTAGGG)n and vertebrates (TTAGGG)n. ii) Asparagales species such as Phormium tenax (Hemerocallidaceae), Muscari comosum (Hyacinthaceae), Narcissus jonquilla (Amaryllidaceae) and Allium sativum (Alliaceae) lack both the plant telomere repeats and the vertebrate telomere repeats. iii) Two other Asparagales species, Aloe vera (Asphodelaceae) and an Iris hybrid (Iridaceae), display positive hybridization with the vertebrate telomere repeats but not with the plant telomere repeats. Southern blot hybridization revealed concurring results. On this basis, the composition of the telomere structure in this plant group is discussed.

Blotting, Southern↗
PubMed2005

Association of the 17-kDa extrinsic protein with photosystem II in higher plants.

The structural association of the spinach 17-kDa extrinsic protein of photosystem II with other extrinsic and membrane-bound components of the photosystem was investigated by labeling the 17-kDa extrinsic protein with the amino-group-specific reagent N-hydroxysuccinimidobiotin both on intact photosystem II membranes or as a free protein in solution. After isolation of the biotinylated molecules, the modified 17-kDa proteins were allowed to rebind to photosystem II membranes which were depleted of the 17-kDa component. Differential binding of the protein biotinylated in solution compared to unmodified 17-kDa protein or 17-kDa protein modified on PS II membranes was observed. This indicated possible steric or ionic interference because of biotinylated lysyl residues present on the protein modified in solution. Biotinylated sites on the different modified 17-kDa proteins were identified by trypsin and Staphylococcus V8 protease digestion, followed by affinity chromatography enrichment of the biotinylated peptides and analysis of the peptide fragment mixture by nanospray liquid chromatography-tandem mass spectrometry. Four lysyl residues that were modified when the protein was biotinylated in solution were not biotinylated when the protein was modified on the PS II membrane (90K, 96K, 101K, and 102K). These residues appear to identify a protein domain involved in the interaction of the 17-kDa protein with the other components of the photosystem.

Amino Acid Sequence↗
PubMed2003

Structural analyses of living plant nuclei.

The nucleus is the cellular organelle in which the bulk of the genomic information is stored. From studies using fluorescence microscopy with optical sections of fixed cells, a picture of an organized nuclear structure has emerged. Recently, the application of the green fluorescent protein (GFP) as a fluorescent dye allows the visualization of nuclear dynamics in live cells. Using four-dimensional fluorescence microscopy, the nuclear structures within an interphase nucleus are perceived to have dynamic domains. Structural analyses of a living plant nucleus contribute to our understanding of the genome information process in a particular cell in multicelluar systems.

Cell Nucleus↗
PubMed1996

Plant serine proteinase inhibitors. Structure and biochemical applications on plasma kallikrein and related enzymes.

The action of two Bowman-Birk and several plant Kunitz-type inhibitors were studied on trypsin, chymotrypsin, plasma kallikrein and factor XII. The primary structure of some of them was completely defined. The results showed that the Bowman-Birk type inhibitors, although potent inhibitors for trypsin (Ki in the range of 1-2 nM), are not able to inhibit plasma kallikrein. Factor XII (Ki = 1.4 microM) and chymotrypsin (Ki = 5.0 nM) are inhibited by Torresea cearensis trypsin inhibitor (TcTI) but not by Dioclea glabra trypsin inhibitor (DgTI). Both inhibitors reactive site regions are highly homologous, and the amino acid residues in P1 position are the same, Lys and His; major differences are in the charge of the C-terminal portion of the molecules. The studied Kunitz-type inhibitors were all able to inhibit plasma kallikrein (Ki between 4 and 80 nM), with the exception of Schizolobium parahyba chymotrypsin inhibitor (SpCI), that is specific for chymotrypsin. All Kunitz-type inhibitors inactivate chymotrypsin, but with a dissociation constant in the range of 0.1 to 0.6 microM. Factor XIIf is inhibited with Ki in the range of 0.1 microM. Bauhinia bauhinioides trypsin inhibitor (BbTI) did not promote factor XIIf inhibition. The Kunitz-type inhibitors are a highly homologous, sharing 60% identity in the N-terminal portion of the loop containing the reactive site, and 28.6% identity in the C-terminal portion of the same loop.

Amino Acid Sequence↗
PubMed1999

Vertebrate-type and plant-type ferredoxins: crystal structure comparison and electron transfer pathway modelling.

Crystallographic analysis of a fully functional, truncated bovine adrenodoxin, Adx(4-108), has revealed the structure of a vertebrate-type [2Fe-2S] ferredoxin at high resolution. Adrenodoxin is involved in steroid hormone biosythesis in adrenal gland mitochondria by transferring electrons from adrenodoxin reductase to different cytochromes P450. Plant-type [2Fe-2S] ferredoxins interact with photosystem I and a diverse set of reductases.A systematic structural comparison of Adx(4-108) with plant-type ferredoxins which share about 20 % sequence identity yields these results. (1) The ferredoxins of both types are partitioned into a large, strictly conserved core domain bearing the [2Fe-2S] cluster and a smaller interaction domain which is structurally different for both subfamilies. (2) In both types, residues involved in interactions with reductase are located at similar positions on the molecular surface and coupled to the [2Fe-2S] cluster via structurally equivalent hydrogen bonds. (3) The accessibility of the [2Fe-2S] cluster differs between Adx(4-108) and the plant-type ferredoxins where a solvent funnel leads from the surface to the cluster. (4) All ferredoxins are negative monopoles with a clear charge separation into two compartments, and all resulting dipoles but one point into a narrow cone located in between the interaction domain and the [2Fe-2S] cluster, possibly controlling predocking movements during interactions with redox partners. (5) Model calculations suggest that FE1 is the origin of electron transfer pathways to the surface in all analyzed [2Fe-2S] ferredoxins and that additional transfer probability for electrons tunneling from the more buried FE2 to the cysteine residue in position 92 of Adx is present in some.

Adrenodoxin↗