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At least 127 records · Page 7Linked to original sources
PubMed2005

Lectins as bioactive plant proteins: a potential in cancer treatment.

Plant lectins, a unique group of proteins and glycoproteins with potent biological activity, occur in foods like wheat, corn, tomato, peanut, kidney bean, banana, pea, lentil, soybean, mushroom, rice, and potato. Thus, dietary intakes by humans can be significant. Many lectins resist digestion, survive gut passage, and bind to gastrointestinal cells and/or enter the circulation intact, maintaining full biological activity. Several lectins have been found to possess anticancer properties in vitro, in vivo, and in human case studies; they are used as therapeutic agents, preferentially binding to cancer cell membranes or their receptors, causing cytotoxicity, apoptosis, and inhibition of tumor growth. These compounds can become internalized into cells, causing cancer cell agglutination and/or aggregation. Ingestion of lectins also sequesters the available body pool of polyamines, thereby thwarting cancer cell growth. They also affect the immune system by altering the production of various interleukins, or by activating certain protein kinases. Lectins can bind to ribosomes and inhibit protein synthesis. They also modify the cell cycle by inducing non-apoptotic G1-phase accumulation mechanisms, G2/M phase cell cycle arrest and apoptosis, and can activate the caspase cascade. Lectins can also downregulate telomerase activity and inhibit angiogenesis. Although lectins seem to have great potential as anticancer agents, further research is still needed and should include a genomic and proteomic approach.

Animals↗
PubMed1993

Characterization of DBPm, a plant protein that binds to DNA containing 5-methylcytosine.

A protein (DBPm) has been isolated from nuclear extracts of soybean seeds, cauliflower florets, corn seed, wheat germ, and pea hypocotyl, seeds, apices, roots, and leaves that specifically binds to double-strand DNA containing 5-methylcytosine residues. In electrophoretic mobility shift assays, non-methylated duplex DNAs competed only slightly, while methylated DNAs were strong competitors. Specific binding still occurred after partial proteolysis of DBPm, but not after heating at 45 degrees C. By ultraviolet light-crosslinking and sodium dodecyl sulfate polyacrylamide gel electrophoresis and gel filtration, the size of pea seed DBPm was estimated to be in the range 70-90 kDa. From equilibrium binding studies the equilibrium constant for binding of pea seed DBPm to a 34 bp duplex deoxyoligonucleotide containing 12 5-methylcytosine residues was 1.2 x 10(9) M-1. The binding properties of DBPm make it a good candidate for a plant protein capable of mediating the effects of DNA methylation on the activity of some plant genes.

5-Methylcytosine↗
PubMed2006

Plant protein inhibitors of cell wall degrading enzymes.

Plant cell walls, which consist mainly of polysaccharides (i.e. cellulose, hemicelluloses and pectins), play an important role in defending plants against pathogens. Most phytopathogenic microorganisms secrete an array of cell wall degrading enzymes (CWDEs) capable of depolymerizing the polysaccharides in the plant host wall. In response, plants have evolved a diverse battery of defence responses including protein inhibitors of these enzymes. These include inhibitors of pectin degrading enzymes such as polygalacturonases, pectinmethyl esterases and pectin lyases, and hemicellulose degrading enzymes such as endoxylanases and xyloglucan endoglucanases. The discovery of these plant inhibitors and the recent resolution of their three-dimensional structures, free or in complex with their target enzymes, provide new lines of evidence regarding their function and evolution in plant-pathogen interactions.

Carboxylic Ester Hydrolases↗
PubMed2006

Identification of a new family of plant proteins loosely related to glutaredoxins with four CxxC motives.

The annotation of the recently released Populus trichocarpa genome, has allowed us to characterize extensively the multigenic families of the redoxin proteins. Proteins with two cysteines separated by two amino acids (CxxC motif) are often involved in redox reactions by promoting the formation, reduction or isomerization of disulfide bonds or by binding prosthetic groups or metals. We report here the presence of a new protein family in higher plants, constituted of 19 members in Populus trichocarpa, 15 in Arabidopsis thaliana and 17 in Oryza sativa. These proteins are almost specific to higher plants, with only two homologous genes found in mammals and arthropoda but none in other kingdoms. While these proteins were predicted as glutaredoxin-like proteins (GRL) in the automatic annotation procedure, they do not share the major conserved features of glutaredoxins but instead they display four conserved CxxC motives. A classification of these proteins, based on sequence similarity, gene structure and predicted cellular localization is proposed. The expression of these genes was also investigated by analyzing EST databases and Arabidopsis microarray results.

Amino Acid Motifs↗
PubMed2004

A major allergen from pollen defines a novel family of plant proteins and shows intra- and interspecies [correction of interspecie] cross-reactivity.

Olive tree (Olea europaea) pollen is a main cause of allergy associated with extensive areas of Europe and North America. Ole e 10, a small (10.8 kDa) and acidic (pI 5.8) protein, has been identified as a major allergen from the olive pollen, isolated, and characterized. Circular dichroism analysis gave 17% alpha helix, 33% beta sheet, and 21% beta turn for its secondary structure. Based on amino acid sequences of tryptic peptides, the protein was cloned and sequenced. The allergen consists of a single polypeptide chain of 102 aa, with a signal peptide of 21 residues. Ole e 10 showed homology with the C-terminal domain of another olive allergen, Ole e 9 (1,3-beta-glucanase, 53% identity), with deduced sequences from Arabidopsis thaliana genes (42-46% identity) and with polypeptide segments (Cys boxes) of proteins involved in yeast development (Epd1/Gas-1p/Phr2 families; 42-43% similarity). Ole e 10 showed 55% prevalence for olive-allergic patients and exhibited an IgE response dependent on its conformation. Remarkable IgE cross-reactivity was detected with Ole e 9, but no correlation was observed between the individual IgE responses to both allergens. Ole e 10 shares IgE B cell epitopes with proteins from Oleaceae, Gramineae, Betulaceae, Chenopodiaceae, Cupressaceae, Ambrosia, and Parietaria pollens, latex, and vegetable foods, such as tomato, kiwi, potato, and peach. These data indicate that Ole e 10 is a new pan-allergenic plant protein that shows notable intra- and interspecie IgE cross-reactivity and is a powerful candidate to be involved in pollen-latex-fruit syndrome.

Adult↗
PubMed2001

Plant protein interactions with polysaccharides and their influence on legume protein functionality. A review.

Associative interactions between proteins and polysaccharides, both coulombic and non-coulombic, lead to the formation of interpolymer complexes. Complex formation with charged polysaccharides, either anionic or cationic, imparts solubility to seed globulins in the vicinity of their isoelectric points. This has been shown for the complexes "sunflower 11 S globulin (helianthinin)--sodium alginate" and "faba bean legumin (or the product of its limited proteolysis with trypsin--legumin-T)--chitosan". Hysteresis effects allow to control the solubility of seed globulins in weakly acid or weakly basic media. Formation of soluble complexes of faba bean legumin or legumin-T with chitosan substantially increases the emulsion stability of the both proteins.

Chitin↗
PubMed2003

Molecular identification of wheat endoxylanase inhibitor TAXI-I1, member of a new class of plant proteins.

Triticum aestivum endoxylanase inhibitors (TAXIs) are wheat proteins that inhibit family 11 endoxylanases commonly used in different (bio)technological processes. Here, we report on the identification of the TAXI-I gene which encodes a mature protein of 381 amino acids with a calculated molecular mass of 38.8 kDa. When expressed in Escherichia coli, the recombinant protein had the specificity and inhibitory activity of natural TAXI-I, providing conclusive evidence that the isolated gene encodes an endoxylanase inhibitor. Bioinformatical analysis indicated that no conserved domains nor motifs common to other known proteins are present. Sequence analysis revealed similarity with a glycoprotein of carrot and with gene families in Arabidopsis thaliana and rice, all with unknown functions. Our data indicate that TAXI-I belongs to a newly identified class of plant proteins for which a molecular function as glycoside hydrolase inhibitor can now be suggested.

Amino Acid Sequence↗
PubMed1997

Molybdenum cofactor biosynthesis. The plant protein Cnx1 binds molybdopterin with high affinity.

The molybdenum cofactor is an essential part of all eukaryotic molybdoenzymes. It is a molybdopterin (MPT) revealing the same core structure in all organisms. The plant protein Cnx1 from Arabidopsis thaliana is involved in the multi-step biosynthesis of molybdenum cofactor. Previous studies (Stallmeyer, B., Nerlich, A., Schiemann, J., Brinkmann, H., and Mendel, R. R. (1995) Plant J. 8, 751-762) suggested a function of Cnx1 in a late step of cofactor biosynthesis distal to the formation of MPT, i.e. conversion of MPT into molybdenum cofactor. Here we present the first biochemical evidences confirming this assumption. The protein Cnx1 consists of two domains (E and G) homologous to two distinct Escherichia coli proteins involved in cofactor synthesis. Binding studies with recombinantly expressed and purified Cnx1 and with its single domains revealed a high affinity of the G domain to MPT (kD = 0.1 microM) with equimolar binding. In contrast, the E domain of Cnx1 binds MPT with lower affinity (kD = 1.6 microM) and in a cooperative manner (nH = 1. 5). The entire Cnx1 showed a tight and cooperative MPT binding. Based on these data providing a common link between both domains that matches the previous characterization of plant and bacterial Cnx1 homologous mutants, we present a model for the function of Cnx1.

Arabidopsis↗
PubMedDate not supplied

A new family of plant antifungal proteins.

Plant seeds contain high concentrations of many antimicrobial proteins. These include chitinases, beta-1,3-glucanases, proteinase inhibitors, and ribosome-inactivating proteins. We recently reported the presence in corn seeds of zeamatin, a protein that has potent activity against a variety of fungi but has none of the above activities. Zeamatin is a 22-kDa protein that acts by causing membrane permeabilization Using a novel bioautography technique, we found similar antifungal proteins in the seeds of 6 of 12 plants examined. A polyclonal antiserum was raised against zeamatin and was used in immunoblots to confirm the presence of zeamatinlike proteins in these seeds. N-terminal amino acid sequencing was carried out on the antifungal proteins from corn, oats, sorghum, and wheat, and these sequences revealed considerable homology with each other. Interestingly, these N-terminal sequences are also similar to those of thaumatin, a pathogenesis-related protein from tobacco, and two salt stress-induced proteins. These results indicate that zeamatin is not unique but is a member of a previously unrecognized family of plant defense proteins that may include some species of pathogenesis-related proteins.

Amino Acid Sequence↗
PubMed2004

Plant protein inhibitors of invertases.

In higher plants, cell wall (CWI) and vacuolar invertases (VI) are important metabolic enzymes, but are also key players during wound and pathogen defense reactions and in several developmental transitions. These multiple functions are implemented by small gene families. While induction of CWI and VI activities usually operates via increased transcription of the corresponding isoform gene, the equally important silencing of invertase activity depends on post-translational mechanisms, including inactivation by specific inhibitor proteins. Recently, the first cDNAs for plant invertase inhibitors were cloned, NtCIF and NtVIF (cell wall/vacuolar inhibitor of beta-fructosidase). The encoded proteins have been expressed in E. coli for functional studies and transgenic tobacco and potato plants were generated to explore the inhibitor function(s) in vivo. Mining the Arabidopsis thaliana genome revealed an inhibitor protein family of limited sequence conservation, some members grouping with tobacco CIF and VIF, while others showing a closer similarity with a recently identified inhibitor of pectin methylesterase. In vitro studies have confirmed target enzyme specificity for invertase and pectin methylesterase inhibitors (PMEI), respectively. The current status of research on invertase inhibitors and the perspectives for their use in plant biotechnology will be discussed.

Abscisic Acid↗
PubMed1996

Signal sequence trap to clone cDNAs encoding secreted or membrane-associated plant proteins.

A method was developed for rapid cloning of plant cDNAs encoding proteins with membrane-spanning domains. A novel expression vector was constructed for expression of plant cDNA libraries in COS cells. Fusion proteins were expressed containing at their N-terminus an endoplasmic reticulum (ER) signal peptide. After entry into the ER these proteins could traffic via the default pathway to the plasma membrane. Trapping at the cell surface occurred when the protein contained one or more membrane-spanning domains. A simple color-based immunoscreening procedure allowed the isolation of cDNAs after only two rounds of COS cell transfection and screening. Several cDNA clones encoding proteins with putative membrane-spanning domains were isolated. Among them were cytochrome b5 and full-length cDNA clones encoding putative secretory proteins targeted to the ER membrane by their N-terminal signal peptide.

Amino Acid Sequence↗
PubMed2003

[The effects of Zheng's plant-protein on the proliferation of lymphocytes from patients with breast cancer and precancer].

AIM: To study the effect of Zheng's plant-protein(ZPP) and phytohemagglutinin(PHA) on proliferation of peripheral blood lymphocytes (PBL) and it's application value on the early diagnosis and therapy of breast cancer. METHODS: The proliferation assay was used (3)H-TdR incorporation test. The phenotypes of PBL were analysised by flow cytometry(FCM). RESULTS: The ZPP significantly and selectively enhanced proliferation activity of PBL of primary breast and precancer cases. Their stimulation indexes(SI) were 3.00+/-1.45 and 2.53+/-0.80, while the SI of simple hyperplasia cases and normal subjecties were 1.18+/-0.47 and 1.06+/-0.91. The former were significantly higher than the latter (P<0.01). The ZPP was also enhanced the expression level of CD3(+),CD4(+) and CD8(+) of PBL. CONCLUSION: This results suggest that ZPP might be a beast cancer common antigen. These activity might be used in clinical implication to diagnosis and treatment of breast cancer.

Breast Neoplasms↗
PubMed2004

Inhibition of plant protein synthesis by the cyanobacterial hepatotoxin, cylindrospermopsin.

Cylindrospermopsin, a cyanobacterial guanidine alkaloid hepatotoxin and protein synthesis-inhibitor, was assayed for its effects on the germination of pollen from tobacco (Nicotiana tabacum cv Samsun NN). Pollen germination, measured by Alcian Blue dye-binding, was inhibited by cylindrospermopsin between 5 and 1000 microg ml(-1). As a protein synthesis-inhibitor, cylindrospermopsin did not inhibit pollen germination to the same extent as cycloheximide on a gravimetric basis, but significantly reduced the amount of (14)C-(U)-l-leucine labelling in pollen tubes. The inhibition of tobacco pollen germination may be amenable for development as a bioassay for cylindrospermopsin, although this would require a pre-concentration step for the monitoring of environmental samples. Implications of these observations for current spray-irrigation practices are discussed.

Alcian Blue↗