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At least 739 records · Page 41Linked to original sources
PubMed1994

Structural similarity of plant chitinase and lysozymes from animals and phage. An evolutionary connection.

A search in the database of known three-dimensional protein structures with the structure of a plant endochitinase revealed a subtle but unambiguous similarity to lysozymes from animals and phages. An evolutionary connection between plant endochitinases and lysozymes is supported by similar overall topology of fold, overlapping substrate specificities and remarkable conservation of some sequence and architectural detail around the active site. Much of the knowledge about lysozyme can now be extended by analogy to endochitinase. New insights into the mechanism of endochitinase are expected to stimulate genetic engineering studies into plant defense mechanisms against pests and pathogens.

Amino Acid Sequence↗
PubMed1999

The evolution of new structures: clues from plant cytoskeletal genes.

How large numbers of genes were recruited simultaneously to build new organ structures is one of the greatest puzzles in evolutionary biology. Here, we present data suggesting that the vegetative and reproductive classes of actins and other cytoskeletal proteins arose concurrently with the macroevolutionary divergence of leaves and reproductive structures in the earliest land plants. That the cytoskeleton is essential for physically programming the development of organs and tissues is well established. Thus, we propose that this regulatory dichotomy represents an ancient landmark event in the global regulation of hundreds of higher-plant genes, an event that is linked to the macroevolution of plant vegetative and reproductive organs. The recent availability of sequence and expression data for large numbers of plant genes should make it possible to dissect this and other major macroevolutionary events.

Actins↗
PubMed2004

New insights from fine-scale spatial genetic structure analyses in plant populations.

Many empirical studies have assessed fine-scale spatial genetic structure (SGS), i.e. the nonrandom spatial distribution of genotypes, within plant populations using genetic markers and spatial autocorrelation techniques. These studies mostly provided qualitative descriptions of SGS, rendering quantitative comparisons among studies difficult. The theory of isolation by distance can predict the pattern of SGS under limited gene dispersal, suggesting new approaches, based on the relationship between pairwise relatedness coefficients and the spatial distance between individuals, to quantify SGS and infer gene dispersal parameters. Here we review the theory underlying such methods and discuss issues about their application to plant populations, such as the choice of the relatedness statistics, the sampling scheme to adopt, the procedure to test SGS, and the interpretation of spatial autocorrelograms. We propose to quantify SGS by an 'Sp' statistic primarily dependent upon the rate of decrease of pairwise kinship coefficients between individuals with the logarithm of the distance in two dimensions. Under certain conditions, this statistic estimates the reciprocal of the neighbourhood size. Reanalysing data from, mostly, published studies, the Sp statistic was assessed for 47 plant species. It was found to be significantly related to the mating system (higher in selfing species) and to the life form (higher in herbs than trees), as well as to the population density (higher under low density). We discuss the necessity for comparing SGS with direct estimates of gene dispersal distances, and show how the approach presented can be extended to assess (i) the level of biparental inbreeding, and (ii) the kurtosis of the gene dispersal distribution.

Demography↗
PubMed2005

Structure of the higher plant light harvesting complex I: in vivo characterization and structural interdependence of the Lhca proteins.

We have investigated the structure of the higher plant light harvesting complex of photosystem I (LHCI) by analyzing PSI-LHCI particles isolated from a set of Arabidopsis plant lines, each lacking a specific Lhca (Lhca1-4) polypeptide. Functional antenna size measurements support the recent finding that there are four Lhca proteins per PSI in the crystal structure [Ben-Shem, A., Frolow, F., and Nelson, N. (2003) Nature 426, 630-635]. According to HPLC analyses the number of pigment molecules bound within the LHCI is higher than expected from reconstitution studies or analyses of isolated native LHCI. Comparison of the spectra of the particles from the different lines reveals chlorophyll absorption bands peaking at 696, 688, 665, and 655 nm that are not present in isolated PSI or LHCI. These bands presumably originate from "gap" or "linker" pigments that are cooperatively coordinated by the Lhca and/or PSI proteins, which we have tentatively localized in the PSI-LHCI complex.

Arabidopsis↗
PubMed1997

Sequence and structural features of plant and fungal tyrosinases.

Tyrosinases from various organisms are compared with respect to enzymatic structure, primary, secondary and tertiary structure, domain structure, Cu binding sites, maturation mechanism and activation mechanism. On the basis of these comparisons, and by using hemocyanin structure as a template, a structure model for the active site of tyrosinases is proposed.

Amino Acid Sequence↗
PubMed1996

Primary structure of the plant serpin BSZ7 having the capacity of chymotrypsin inhibition.

The primary structure of barley grain serpin BSZ7 was deduced from a cDNA encoding 397 amino-acid residues. More than 70% of the residues were confirmed by sequencing peptide fragments. The N-terminus was identified as an acetylated Ala by using mass spectrometry coupled with amino-acid analysis. None of the four putative N-glycosylation sites were found to be glycosylated. The positional identity of BSZ7 with plant and mammalian serpins is 69-72% and 25-32%, respectively.

Amino Acid Sequence↗
PubMed1993

Transcription regulatory proteins in higher plants.

Novel structures and interactions for plant transcription factors have recently been reported. Factors that lack DNA-binding activity, exhibit putative triple-helix DNA-binding motifs, or possess two DNA-binding domains are among the interesting results. Advances in our understanding of protein-protein interactions between plant transcription factors are facilitating the design of new experimental strategies to further define their roles in regulatory pathways.

Amino Acid Sequence↗
PubMed1995

The human glioma pathogenesis-related protein is structurally related to plant pathogenesis-related proteins and its gene is expressed specifically in brain tumors.

We report the cloning of a cDNA encoding GliPR (glioma pathogenesis-related protein), a protein that is structurally similar to plant pathogenesis-related proteins. The GLIPR gene is highly expressed in the human brain tumor, glioblastoma multiforme/astrocytoma, but neither in normal fetal or adult brain tissue, nor in other nervous system tumors. GliPR shares up to 50% amino acid (aa) homology with plant pathogenesis-related proteins, group 1, over a region that comprises almost two thirds of the protein. We speculate that there may be functional similarities between the human and plant proteins as well.

Amino Acid Sequence↗
PubMed1994

Cloning of four cyclins from maize indicates that higher plants have three structurally distinct groups of mitotic cyclins.

While a large number of cyclins have been described in animals and yeasts, very limited information is available regarding cyclins in plants. We describe here the isolation of cDNA clones encoding four putative mitotic cyclins from maize. All four cyclins were able to induce maturation of Xenopus oocytes, demonstrating that they can act as mitotic cyclins in this system. Northern analysis showed that all four cyclins were expressed only in actively dividing tissues and organs, with a stronger correlation between expression and mitotic activity than is observed with cdc2. The deduced protein sequences suggest that the four maize cyclins belong to the cyclin A and B families identified from animal and yeast studies but that they cannot be described easily as either A-type or B-type cyclins. However, comparison with previously cloned plant cyclins shows that cyclins in higher plants form three distinct structural groups that have been conserved in both monocotyledonous and dicotyledonous species and that cyclins from all three groups are present within a single plant species.

Amino Acid Sequence↗
PubMed2005

Structural relatedness of plant food allergens with specific reference to cross-reactive allergens: an in silico analysis.

BACKGROUND: The body of sequence and structural information on allergens and the sequence analysis of whole plant genomes are facilitating the application of bioinformatic approaches to identifying and defining plant allergens. OBJECTIVE: An in silico approach was used to quantify the distribution of plant food allergen sequences across protein families and to develop and apply a novel means of assessing conserved surface features important for IgE cross-reactivity. METHODS: Plant food allergen sequences were classified into Pfam families on the basis of sequence homology. Contact surface areas of selected proteins were calculated with MOLMOL by using a 1.4-A probe, corrected by removing contributions from IgE inaccessible main chains and side chains forming the ligand binding sites. RESULTS: A set of 129 food allergen sequences were classified into only 20 of 3849 possible Pfam families, with 4 families accounting for more than 65% of food allergens. Structural bioinformatic analysis of conserved exterior main chains and amino acid side chains in cross-reactive homologues of Bet v 1 and nonspecific lipid transfer proteins showed higher levels of similarity than shown by simple sequence comparisons. Thus, 75% of the Mal d 1 surface is likely to bind anti-Bet v 1 antibodies, compared with a sequence identity of approximately 56%. CONCLUSION: Most plant food allergens belong to only 4 structural families, indicating that conserved structures and biological activities may play a role in determining or promoting allergenic properties. Structural bioinformatic analysis shows that conservation of 3-dimensional structure should be included in any assessment of potential IgE cross-reactivity in, for example, novel proteins.

Allergens↗
PubMed1994

Three-dimensional structures of two plant beta-glucan endohydrolases with distinct substrate specificities.

The three-dimensional structures of (1-->3)-beta-glucanase (EC 3.2.1.39) isoenzyme GII and (1-->3,1-->4)-beta-glucanase (EC 3.2.1.73) isoenzyme EII from barley have been determined by x-ray crystallography at 2.2- to 2.3-A resolution. The two classes of polysaccharide endohydrolase differ in their substrate specificity and function. Thus, the (1-->3)-beta-glucanases, which are classified amongst the plant "pathogenesis-related proteins," can hydrolyze (1-->3)- and (1-->3,1-->6)-beta-glucans of fungal cell walls and may therefore contribute to plant defense strategies, while the (1-->3,1-->4)-beta-glucanases function in plant cell wall hydrolysis during mobilization of the endosperm in germinating grain or during the growth of vegetative tissues. Both enzymes are alpha/beta-barrel structures. The catalytic amino acid residues are located within deep grooves which extend across the enzymes and which probably bind the substrates. Because the polypeptide backbones of the two enzymes are structurally very similar, the differences in their substrate specificities, and hence their widely divergent functions, have been acquired primarily by amino acid substitutions within the groove.

Base Sequence↗
PubMed1993

Plant antitumor agents. 30. Synthesis and structure activity of novel camptothecin analogs.

A large number of camptothecin (CPT) analogs have been prepared in the 20S, 20RS, and 20R configurations with a number of ring A substituents. Topoisomerase I (T-I) inhibition data (IC50) have been obtained by standard procedures. In general, substitution at the 9 or 10 positions with amino, halogeno, or hydroxyl groups in compounds with 20S configuration results in compounds with enhanced T-I inhibition. Compounds in the 20RS configuration were less active in vitro and in vivo and those in the 20R configuration were inactive. Compounds with 10,11-methylenedioxy substitution on ring A displayed a marked increase in potency in the T-I inhibition assay. The activities of some of the analogs as determined in a variety of in vivo assays including the L-1210 mouse leukemia assay were, in general, in accord with T-I inhibition. A number of water-soluble analogs such as 20-glycinate esters, 9-glycinamides, or hydrolyzed lactone salts were prepared and tested in in vitro and in vivo assays. In general, these compounds were less active than CPT both in terms of T-I inhibition and life prolongation in the L-1210 assay. However, certain 20-glycinate esters showed good in vivo activity after iv administration.

Animals↗
PubMed2000

The structural properties of plant peroxisomes and their metabolic significance.

Plant peroxisomes can be isolated by Percoll density gradient centrifugation at high purity and metabolic competence as well as in relatively large quantities. According to biochemical and electrophysiological analyses, plant peroxisomes have recently been shown to differ from other cell organelles in essential structural properties. Unlike mitochondria or plastids, compartmentalization of plant peroxisomal metabolism is in major parts not caused by a boundary function of the membrane but is primarily due to the specific structure of the protein matrix. The enzymes of the photorespiratory C2 cycle of leaf peroxisomes are arranged as multienzyme complexes that allow efficient metabolic channelling with high flux rates and minimum leakage of reactive oxygen species from the organelle. Transfer of metabolites, such as carboxylates, proceeds across the peroxisomal membrane via a porin-like channel, which represents a relatively unspecific but highly efficient transport system. Because all variants of peroxisomes, which all contain only a single boundary membrane, are confronted with the task of transporting a large group of metabolites while preventing the escape of reactive intermediates, it is reasonable to speculate that the unique compartmentalization feature of leaf peroxisomes also applies to peroxisomes from fungi and mammals.

Biological Transport↗
PubMed2006

Plant thionins--the structural perspective.

Thionins belong to a rapidly growing family of biologically active peptides in the plant kingdom. Thionins are small ( approximately 5 kDA), cysteine-rich peptides with toxic and antimicrobial properties. They show a broad cellular toxicity against wide range of organisms and eukaryotic cell lines; while possessing some selectivity. Thionins are believed to be involved in protection against plant pathogens, including bacteria and fungi, by working directly at the membrane. The direct mechanism of action is still surrounded by controversy. Here the results of structural studies are reviewed and confronted with recent results of biophysical studies aimed at defining the function of thionins. The proposed toxicity mechanisms are reviewed and the attempt to reconcile competing hypotheses with a wealth of structural and functional studies is made.

Amino Acid Sequence↗
PubMed1991

Plant enolase: gene structure, expression, and evolution.

Enolase genes were cloned from tomato and Arabidopsis. Comparison of their primary structures with other enolases revealed a remarkable degree of conservation, except for the presence of an insertion of 5 amino acids unique to plant enolases. Expression of the enolase genes was studied under various conditions. Under normal growth conditions, steady-state messenger and enzyme activity levels were significantly higher in roots than in green tissue. Large inductions of mRNA, accompanied by a moderate increase in enzyme activity, were obtained by an artificial ripening treatment in tomato fruits. However, there was little effect of anaerobiosis on the abundance of enolase messenger. In heat shock conditions, no induction of enolase mRNA was observed. We also present evidence that, at least in Arabidopsis, the hypothesis that there exists a complete set of glycolytic enzymes in the chloroplast is not valid, and we propose instead the occurrence of a substrate shuttle in Arabidopsis chloroplasts for termination of the glycolytic cycle.

Amino Acid Sequence↗
PubMed1992

Indonesian medicinal plants. II. Chemical structures of Pongapinones A and B, two new phenylpropanoids from the bark of Pongamia pinnata (Papilionaceae).

Two new phenylpropanoids named pongapinone A (1) and pongapinone B (2) were isolated from the bark of Pongamia pinnata (Papilionaceae), an Indonesian medicinal plant, and their chemical structures have been elucidated on the basis of their physicochemical properties. Pongapinone A (1) was found to inhibit interleukin-1 production.

Chromones↗
PubMed1994

Function of Oxidative Cross-Linking of Cell Wall Structural Proteins in Plant Disease Resistance.

Elicitation of soybean cells causes a rapid insolubilization of two cell wall structural proteins, p33 and p100. Likewise, a short elicitation of 30 min rendered cell walls more refractory to enzyme digestion as assayed by the yield of protoplasts released. This effect could be ascribed to protein cross-linking because of its insensitivity to inhibitors of transcription (actinomycin D) and translation (cycloheximide) and its induction by exogenous H2O2. Moreover, the induced loss of protoplasts could be prevented by preincubation with DTT, which also blocks peroxidase-mediated oxidative cross-linking. The operation of protein insolubilization in plant defense was also demonstrated by its occurrence in the incompatible interaction but not in the compatible interaction between soybean and Pseudomonas syringae pv glycinea. Likewise, protein insolubilization was observed in bean during non-host hypersensitive resistance to the tobacco pathogen P. s. pv tabaci mediated by the hypersensitive resistance and pathogenicity (Hrp) gene cluster. Our data strongly suggest that rapid protein insolubilization leads to a strengthened cell wall, and this mechanism functions as a rapid defense in the initial stages of the hypersensitive response prior to deployment of transcription-dependent defenses.

Journal Article↗