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At least 1,099 records · Page 61Linked to original sources
PubMed2003

Structure of Petunia hybrida defensin 1, a novel plant defensin with five disulfide bonds.

The structure of a novel plant defensin isolated from the flowers of Petunia hybrida has been determined by (1)H NMR spectroscopy. P. hybrida defensin 1 (PhD1) is a basic, cysteine-rich, antifungal protein of 47 residues and is the first example of a new subclass of plant defensins with five disulfide bonds whose structure has been determined. PhD1 has the fold of the cysteine-stabilized alphabeta motif, consisting of an alpha-helix and a triple-stranded antiparallel beta-sheet, except that it contains a fifth disulfide bond from the first loop to the alpha-helix. The additional disulfide bond is accommodated in PhD1 without any alteration of its tertiary structure with respect to other plant defensins. Comparison of its structure with those of classic, four-disulfide defensins has allowed us to identify a previously unrecognized hydrogen bond network that is integral to structure stabilization in the family.

Amino Acid Sequence↗
PubMed1993

cAMP Regulates Infection Structure Formation in the Plant Pathogenic Fungus Magnaporthe grisea.

Magnaporthe grisea, the causal agent of rice blast, is one of the most destructive fungal pathogens of rice throughout the world. Infection of rice by M. grisea requires the formation of an appressorium, a darkly pigmented, dome-shaped structure. The germ tube tip differentiates into an appressorium following germination of conidia on a leaf surface. When conidia germinate on growth medium or other noninductive surfaces, the emerging germ tube does not differentiate and continues to grow vegetatively. Little is known about the endogenous or exogenous signals controlling the developmental process of infection structure formation. We show here that a hydrophobic surface was sufficient for the induction of the appressorium. Furthermore, we demonstrate that the addition of cAMP, its analogs (8-bromo cAMP and N6-monobutyryl cAMP), or 3-isobutyl-1-methylxanthine (an inhibitor of phosphodiesterase) to germinating conidia or to vegetative hyphae induced appressorium formation on noninductive surfaces. The identification of cAMP as a mediator of infection structure formation provides a clue to the regulation of this developmental process. Elucidation of the mechanism involved is not only of biological interest but may also provide the basis for new disease control strategies.

Journal Article↗
PubMed2005

Idiosyncratic behaviour of tRNA-like structures in translation of plant viral RNA genomes.

Tobacco mosaic virus (TMV) and Nemesia ring necrosis virus (NeRNV) belong to the Tobamoviridae and Tymoviridae families, respectively. Although their RNAs present different 5'-untranslated regions and different family-specific genomic organizations, they share common 3'-ends organized into three consecutive pseudoknot structures followed by a histidylatable tRNA-like structure (TLS). We investigate here whether the histidine residue becomes incorporated into viral proteins and if the TLSs of TMV and NeRNV play a role in viral translation. Our results indicate that, regardless of the genomic context, the histidine moiety does not become incorporated in proteins via ribosomal translation, and that disruption of the TLS in either viral RNA does not perturb the viral translation patterns. In the light of the present data and of previous results on tymoviral TLSVal and bromoviral TLSTyr showing differential effects on translation, we suggest that the key role for the TLS in promoting translation initiation appears to be dictated by the TLS architecture and identity.

Genome, Viral↗
PubMed2000

Beta(1,2)-xylose and alpha(1,3)-fucose residues have a strong contribution in IgE binding to plant glycoallergens.

Primary structures of the N-glycans of two major pollen allergens (Lol p 11 and Ole e 1) and a major peanut allergen (Ara h 1) were determined. Ole e 1 and Ara h 1 carried high mannose and complex N-glycans, whereas Lol p 11 carried only the complex. The complex structures all had a beta(1,2)-xylose linked to the core mannose. Substitution of the proximal N-acetylglucosamine with an alpha(1, 3)-fucose was observed on Lol p 11 and a minor fraction of Ole e 1 but not on Ara h 1. To elucidate the structural basis for IgE recognition of plant N-glycans, radioallergosorbent test analysis with protease digests of the three allergens and a panel of glycoproteins with known N-glycan structures was performed. It was demonstrated that both alpha(1,3)-fucose and beta(1,2)-xylose are involved in IgE binding. Surprisingly, xylose-specific IgE antibodies that bound to Lol p 11 and bromelain did not recognize closely related xylose-containing structures on horseradish peroxidase, phytohemeagglutinin, Ole e 1, and Ara h 1. On Lol p 11 and bromelain, the core beta-mannose is substituted with just an alpha(1,6)-mannose. On the other xylose-containing N-glycans, an additional alpha(1,3)-mannose is present. These observations indicate that IgE binding to xylose is sterically hampered by the presence of an alpha(1,3)-antenna.

Allergens↗
PubMed1998

Characterization of soybean seed coat peroxidase: resonance Raman evidence for a structure-based classification of plant peroxidases.

Electronic absorption and resonance Raman spectra of ferric and ferrous forms of a peroxidase from soybean seed coat (SBP) at neutral and alkaline pH values together with the spectra of the ferric-fluoride complex are reported. At neutral pH a quantum mechanically mixed spin state, resulting from the admixture of intermediate spin, S = 3/2, and high spin, S = 5/2, configurations, has been identified which coexists with five- and six-coordinate high-spin hemes. A complete conversion to a fluoride-ligated six-coordinate high-spin and a hydroxy-ligated six-coordinate low-spin heme are observed at acid pH in the presence of fluoride and at alkaline pH, respectively. The spectral features suggest that both the fluoride and hydroxo ligands are stabilized by hydrogen-bond interactions with the distal Arg residue and through a water molecule with the distal His residue. The ferrous form shows a single nu(Fe-Im) at 246 cm(-1) at neutral pH. The data indicate that SBP shares many characteristics with peroxidases belonging to class III of the "plant peroxidase" superfamily.

Arginine↗
PubMed2001

Medicinal flowers. IV. Marigold. (2): Structures of new ionone and sesquiterpene glycosides from Egyptian Calendula officinalis.

Following the characterization of hypoglycemic, gastric emptying inhibitory, and gastroprotective principles and the structure elucidation of calendasaponins A, B, C, and D, two new ionone glucosides (officinosides A and B), and two sesquiterpene oligoglycosides (officinosides C and D), were isolated from the flowers of Egyptian Calendula officinalis. The structures of the officinosides were elucidated on the basis of chemical and physicochemical evidence.

Calendula↗
PubMed1996

Three-dimensional structure of glutathione S-transferase from Arabidopsis thaliana at 2.2 A resolution: structural characterization of herbicide-conjugating plant glutathione S-transferases and a novel active site architecture.

Glutathione S-transferases (GST) are a family of multifunctional enzymes involved in the metabolization of a broad variety of xenobiotics and reactive endogenous compounds. The interest in plant glutathione S-transferases may be attributed to their agronomic value, since it has been demonstrated that glutathione conjugation for a variety of herbicides is the major resistance and selectivity factor in plants. The three-dimensional structure of glutathione S-transferase from the plant Arabidopsis thaliana has been solved by multiple isomorphous replacement and multiwavelength anomalous dispersion techniques at 3 A resolution and refined to a final crystallographic R-factor of 17.5% using data from 8 to 2.2 A resolution. The enzyme forms a dimer of two identical subunits each consisting of 211 residues. Each subunit is characterized by the GST-typical modular structure with two spatially distinct domains. Domain I consists of a central four-stranded beta-sheet flanked on one side by two alpha-helices and on the other side by an irregular segment containing three short 3(10)-helices, while domain II is entirely helical. The dimeric molecule is globular with a prominent large cavity formed between the two subunits. The active site is located in a cleft situated between domains I and II and each subunit binds two molecules of a competitive inhibitor S-hexylglutathione. Both hexyl moieties are oriented parallel and fill the H-subsite of the enzyme's active site. The glutathione peptide of one inhibitor, termed productive binding, occupies the G-subsite with multiple interactions similar to those observed for other glutathione S-transferases, while the glutathione backbone of the second inhibitor, termed unproductive binding, exhibits only weak interactions mediated by two polar contacts. A most striking difference from the mammalian glutathione S-transferases, which share a conserved catalytic tyrosine residue, is the lack of this tyrosine in the active site of the plant glutathione S-transferase.

Amino Acid Sequence↗
PubMed1994

Pironetin, a novel plant growth regulator produced by Streptomyces sp. NK10958. II. Structural elucidation.

A novel plant growth regulator, pironetin was isolated from the culture broth of Streptomyces sp. NK10958. The structure of pironetin was determined to be (5R,6R)-5-ethyl- 5,6-dihydro-6-[(E)-(2R,3S,4R,5S)-2-hydroxy-4-methoxy-3,5-dimethyl-7- nonenyl]-2H-pyran-2-one by FAB-MS, 1H and 13C NMR, COSY, COLOC, DEPT, IR, X-ray crystallographic analyses and adapted Mosher's method.

Crystallography, X-Ray↗
PubMed2000

Expression of a plant virus non-structural protein in Saccharomyces cerevisiae causes membrane proliferation and altered mitochondrial morphology.

Carnation Italian ringspot tombusvirus encodes a protein, referred to as 36K, that possesses a mitochondrial targeting signal and two transmembrane segments which are thought to anchor this protein to the outer membrane of the mitochondrial envelope of infected plant cells. To determine the topology of the virus protein inserted in the cell membrane, as well as the sequence requirements for targeting and insertion, an in vivo system was set up in which this could be analysed in the absence of productive virus infection. The 36K protein was expressed in the yeast Saccharomyces cerevisiae in native form or fused to the green fluorescent protein. Using a fluorescence microscope, large green-fluorescing cytoplasmic aggregates were visible which stained red when cells were treated with the vital stain MitoTracker, which is specific for mitochondria. These aggregates were shown by electron microscopy to be composed of either mitochondria or membranes. The latter type was particularly abundant for the construct in which the green fluorescent protein was fused at the N terminus of the 36K protein. Immunoelectron microscopy demonstrated that the viral protein is present in the anomalous aggregates and Western blot analysis of protein extracts showed 36K to be resistant to alkaline, urea or salt extraction, a property of integral membrane proteins.

Cell Membrane↗
PubMed2000

A new germacranolide from Artemisia pallens.

A new germacranolide has been isolated from the aerial parts of Artemisia pallens and the structure was established as 4,5 beta-epoxy-10 beta-hydroxy-1-en-3-one-trans-germacran-6 alpha,12-olide (1) by comparison with its 10 alpha-epimer isolated from the same plant.

Anti-Infective Agents↗
PubMed1982

Histone variants in plants. Evidence for primary structure variants differing in molecular weight.

Variants of H2a and H2b histones from wheat embryos and pea shoots have been isolated and characterized by two-dimensional gel electrophoresis, amino acid content, and peptide mapping. In striking contrast to the animal H2a or H2b variants which co-migrate on sodium dodecyl sulfate polyacrylamide gels, their plant counterparts have differential electrophoretic mobilities. The estimated molecular weights of the wheat H2a variants range from 16,600 to 19,000. The H2b variants range from 15,300 to 19,000. Correlating with their electrophoretic mobilities, the plant histone variants elute differentially from gel exclusion columns in a manner consistent with the molecular weight differences inferred from the sodium dodecyl sulfate gels. The differences in peptide maps of the wheat H2a variants are extensive and indicate amino acid substitutions throughout the molecules. The maps of the plant H2a histones are also distinct from those of the major calf thymus H2a histones. The peptide maps of the plant H2b variants are very similar to each other but are markedly different from those of calf thymus H2b histones.

Amino Acid Sequence↗
PubMed1989

Expression of a functional monocotyledonous phytochrome in transgenic tobacco.

A chimeric oat phytochrome structural gene with an uninterrupted coding region was constructed for expression of the monocot protein in transgenic plants. The structural gene was placed under the transcriptional control of either a light-regulated oat phytochrome promoter or the constitutively active cauliflower mosaic virus 35S promoter. These genes were then introduced into Nicotiana tabacum and N.plumbaginifolia. None of the regenerated plants showed expression of oat phytochrome RNA when transcription was controlled by the oat promoter. In contrast, RNA was obtained in plants when the structural gene was functionally linked to the 35S promoter. Transformants expressing oat phytochrome RNA produced a full length 124-kd polypeptide that was recognized by oat-specific anti-phytochrome monoclonal antibodies. The oat protein was a substrate for chromophore addition in tobacco as judged by its red/far-red photoreversible sensitivity to trypsin degradation. Production of oat phytochrome in transgenic plants gave rise to increased phytochrome spectral activity in both light- and dark-grown plants. This increased phytochrome content resulted in phenotypic changes in transformed plants, including semi-dwarfism, darker green leaves, increased tillering and reduced apical dominance. The possible significance of expressing a biologically active phytochrome in transgenic plants is discussed.

Journal Article↗
PubMed2002

In vivo three-dimensional imaging of plants with optical coherence microscopy.

Achieving the ability to non-destructively, non-invasively examine subsurface features of living multicellular organisms at a microscopic level is currently a challenge for biologists. Optical coherence microscopy (OCM) is a new photonics-based technology that can be used to address this challenge. OCM takes advantage of refractive properties of biological molecules to generate three-dimensional images that can be viewed with a computer. We describe new data processing techniques and a different visualization algorithm that substantially improve OCM images. We have applied OCM imaging, in conjunction with these improvements, to a variety of structures of plants, including leaves, flowers, ovules and germinating seeds, and describe the visualization of cellular and subcellular structures within intact plants. We present evidence, based on detailed examination of our OCM images, comparisons to classical plant anatomy studies, and current knowledge of light scattering by cells and their components, that we can distinguish nuclei, organelles and vacuoles. Detailed examination of vascular tissue, which contains cells with elaborate wall structure, shows that cell walls produce no significant OCM signal. These improvements to the visualization process, together with the powerful non-invasive, non-destructive aspects of the technology, will broaden the application of OCM to questions in studies of plants as well as animals.

Arabidopsis↗
PubMed2000

Modular domain structure of Arabidopsis COP1. Reconstitution of activity by fragment complementation and mutational analysis of a nuclear localization signal in planta.

The Arabidopsis COP1 protein functions as a developmental regulator, in part by repressing photomorphogenesis in darkness. Using complementation of a cop1 loss-of-function allele with transgenes expressing fusions of cop1 mutant proteins and beta-glucuronidase, it was confirmed that COP1 consists of two modules, an amino terminal module conferring a basal function during development and a carboxyl terminal module conferring repression of photomorphogenesis. The amino-terminal zinc-binding domain of COP1 was indispensable for COP1 function. In contrast, the debilitating effects of site-directed mutations in the single nuclear localization signal of COP1 were partially compensated by high-level transgene expression. The carboxyl-terminal module of COP1, though unable to substantially ameliorate a cop1 loss-of-function allele on its own, was sufficient for conferring a light-quality-dependent hyperetiolation phenotype in the presence of wild-type COP1. Moreover, partial COP1 activity could be reconstituted in vivo from two non-covalently linked, complementary polypeptides that represent the two functional modules of COP1. Evidence is presented for efficient association of the two sub-fragments of the split COP1 protein in Arabidopsis and in a yeast two-hybrid assay.

Arabidopsis↗
PubMed2002

[Studies on the chemical constituents of Lycianthes biflora].

AIM: To study the chemical constituents of Lycianthes biflora. METHODS: Column chromatography was used to separate the chemical constituents. IR, MS, 1HNMR, 13CNMR and 2D-NMR technique were used to determine the structures of the isolated constituents. RESULTS: Five compounds were isolated from this plant. Their structures were identified to be bifloride A (1), N-trans-cinnamoyltyramine (2), liquiritigenin (3), N-trans-p-coumaroyloctopamine (4), 1-O-beta-D-glucopyranosyl-2-N-2'-hydroxypalmitoyl-sphinga-4- trans-8-trans-dienine (5). CONCLUSION: Compounds 1 and 2 are new compounds, the others were isolated from this plant for the first time. Compound 2 showed inhibitory effects on P-388.

4-Butyrolactone↗
PubMed2001

Homologues of archaeal rhodopsins in plants, animals and fungi: structural and functional predications for a putative fungal chaperone protein.

The microbial rhodopsins (MR) are homologous to putative chaperone and retinal-binding proteins of fungi. These proteins comprise a coherent family that we have termed the MR family. We have used modeling techniques to predict the structure of one of the putative yeast chaperone proteins, YRO2, based on homology with bacteriorhodopsins (BR). Availability of the structure allowed depiction of conserved residues that are likely to be of functional significance. The results lead us to predict an extracellular protein folding function and a transmembrane proton transport pathway. We suggest that protein folding is energized by a novel mechanism involving the proton motive force. We further show that MR family proteins are distantly related to a family of fungal, animal and plant proteins that include the human lysosomal cystine transporter (LCT) of man (cystinosin), mutations in which cause cystinosis. Sequence and phylogenetic analyses of both the MR family and the LCT family are reported. Proteins in both families are of the same approximate size, exhibit seven putative transmembrane alpha-helical spanners (TMSs) and show limited sequence similarity. We show that the LCT family arose by an internal gene duplication event and that TMSs 1-3 are homologous to TMSs 5-7. Although the same could not be demonstrated statistically for MR family members, homology with the LCT family suggests (but does not prove) a common evolutionary pathway. Thus, TMSs 1-3 and 5-7 in both LCT and MR family members may share a common origin, accounting for their shared structural features.

Amino Acid Sequence↗