5 results on '"Thionin"'
Search Results
2. Hordothionins inhibit protein synthesis at the level of initiation in the wheat-germ system
- Author
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Janna Brümmer, Hubert Thole, and Klaus Kloppstech
- Subjects
Hot Temperature ,Biology ,Biochemistry ,Cell-free system ,chemistry.chemical_compound ,Eukaryotic translation ,Polysome ,Protein biosynthesis ,RNA, Messenger ,Peptide Chain Initiation, Translational ,Heat-Shock Proteins ,Triticum ,Plant Proteins ,Protein Synthesis Inhibitors ,Plants, Medicinal ,Methionine ,Protoplasts ,food and beverages ,Fabaceae ,Hordeum ,Translation (biology) ,Thionin ,Kinetics ,chemistry ,Polyribosomes ,Protein Biosynthesis ,Seeds ,RNA ,Hordeum vulgare ,Poly A ,Antimicrobial Cationic Peptides - Abstract
The inhibitory effect of pure alpha and beta hordothionins on protein synthesis directed by pea mRNA has been studied in the wheat-germ translation system. It is demonstrated that a component of the wheat germ counteracts the thionin effect. Formation of polysomes in vitro in the presence of thionin was inhibited to the same extent as the total translation system while run-off translation of isolated polysomes from pea plants was not affected by thionin. These data are consistent with an effect of thionin on the initiation reaction. Analyses of the formation of initiation complexes in the presence and absence of mRNA support this view and show that thionin interferes with the formation of the 43S complex. In accordance with this observation and in contrast to earlier studies no evidence has been obtained for a direct interaction between mRNAs and thionins. The analysis of the translation products also gave no indication for preferential translation of individual mRNAs by the thionin-inhibited translation system. Compared to translation in vitro, exposure of barley protoplasts to thionins showed a less dramatic effect on protein synthesis as measured by incorporation of [35S]methionine into proteins. These data are discussed with respect to the effects of thionins on the plasma membranes as shown previously with animal cell cultures. It is concluded that at least in barley such effects would need higher concentrations of thionins than are required for the inhibition of protein synthesis.
- Published
- 1994
3. Isolation and characterization of cDNAs encoding viscotoxins of mistletoe (Viscum album)
- Author
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Klaus Apel and Gesine Schrader
- Subjects
Signal peptide ,Molecular Sequence Data ,Loranthaceae ,Biology ,Biochemistry ,chemistry.chemical_compound ,Complementary DNA ,Viscotoxins ,Lectins ,Sequence Homology, Nucleic Acid ,Viscum album ,Amino Acid Sequence ,RNA, Messenger ,Cloning, Molecular ,Plant Proteins ,Toxins, Biological ,Immunoassay ,Plants, Medicinal ,Molecular mass ,Nucleic acid sequence ,food and beverages ,DNA ,biology.organism_classification ,Thionin ,Mistletoe ,Molecular Weight ,Ribosome Inactivating Proteins, Type 2 ,chemistry ,Protein Biosynthesis ,RNA ,Electrophoresis, Polyacrylamide Gel ,Plant Preparations ,Plant Lectins ,Poly A - Abstract
Viscotoxins have been isolated from leaf homogenates of European mistletoe (Viscum album L.) and purified to apparent homogeneity. Antisera raised against these polypeptides were used to screen a cDNA expression library in lambda gt11. Two positive clones have been isolated, one encoding a full-length preprotein of viscotoxin A3 and the other encoding the precursor of viscotoxin B. Besides the viscotoxin domain the precursor contained a signal sequence and an acidic polypeptide domain. Similar higher molecular mass precursor proteins have been described for thionins of leaves and seeds of barley. Even though the acidic part of the viscotoxin precursor is much shorter than the corresponding domain of the precursors of the leaf and seed thionins of barley, both the negative charge and the number and the relative position of cysteine residues have been conserved within the acidic domain. This result is consistent with our proposal that the acidic domain of the thionin precursor may play an important role in keeping the thionin inactive within the plant cell.
- Published
- 1991
4. Primary structure and inhibition of protein synthesis in eukaryotic cell-free system of a novel thionin, gamma-hordothionin, from barley endosperm
- Author
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Enrique Méndez, Fernando Soriano, Aurora Moreno, Cesar de Haro, Matilde Salinas, Raul Mendez, Gabriel G. Limas, Fernando Pelaez, and Francisco J. Colilla
- Subjects
Molecular Sequence Data ,Biology ,Biochemistry ,Endosperm ,chemistry.chemical_compound ,Reticulocyte ,medicine ,Protein biosynthesis ,Electrophoresis, Gel, Two-Dimensional ,Trypsin ,Amino Acid Sequence ,Sulfhydryl Compounds ,Amino Acids ,Chromatography, High Pressure Liquid ,Plant Proteins ,Gel electrophoresis ,chemistry.chemical_classification ,Protein Synthesis Inhibitors ,Cell-Free System ,Hydrolysis ,Phosphotransferases ,Protein primary structure ,Hordeum ,Thionin ,Amino acid ,medicine.anatomical_structure ,chemistry ,Protein Biosynthesis ,Seeds ,Hordeum vulgare ,Oxidation-Reduction ,Antimicrobial Cationic Peptides - Abstract
A new sulfur-rich and basic polypeptide, designated as gamma-hordothionin, has been isolated from barley endosperm by a semi-preparative purification consisting of extraction with a volatile salt solution followed by high-performance liquid chromatography using a reversed-phase C4 column. The isolated polypeptide was found to be homogeneous by micro-two-dimensional gel electrophoresis in the presence of sodium dodecyl sulfate. The complete primary structure of gamma-hordothionin was determined by automatic degradation of the intact, S-carboxymethylated and S-pyridylethylated gamma-hordothionin and fragments obtained by proteolytic cleavage. gamma-Hordothionin consists of a single polypeptide chain of 47 amino acids with a calculated molecular mass of 5250 Da and contains four disulfide bridges. gamma-Hordothionin inhibits translation in cell-free systems derived from mammalian (rabbit reticulocyte, mouse liver) as well as non-mammalian (Artemia embryo) cells, at several levels. At low concentrations (1-10 microM) the protein seems to affect mainly the polypeptide-chain-initiation process, although it might also act at the elongation level. At higher concentrations (20-80 microM) this inhibitor induces activation of an eukaryotic polypeptide-chain initiation factor 2 alpha-subunit (eIF-2 alpha) kinase in hemin-supplemented reticulocyte lysates, as does hemin deficiency. The presence of the disulfide bridges in gamma-hordothionin appears to be essential for the eIF-2 alpha kinase activation. Based on its similarity at both the structural and functional level with the different genetic variants of thionins (alpha and beta-thionins, from wheat and barley), gamma-hordothionin is a putative member of the thionin family.
- Published
- 1990
5. Cloning and nucleotide sequence of a cDNA encoding the precursor of the barley toxin alpha-hordothionin
- Author
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Fernando Ponz, Javier Paz-Ares, C. Hernandez-Lucas, Pilar Carbonero, and Francisco García-Olmedo
- Subjects
Immunodiffusion ,Biología ,Mutant ,Biology ,Biochemistry ,Endosperm ,03 medical and health sciences ,chemistry.chemical_compound ,Protein sequencing ,Complementary DNA ,Cloning, Molecular ,Protein Precursors ,Plant Proteins ,030304 developmental biology ,2. Zero hunger ,chemistry.chemical_classification ,0303 health sciences ,Base Sequence ,cDNA library ,Lysine ,030302 biochemistry & molecular biology ,Nucleic acid sequence ,Nucleic Acid Hybridization ,food and beverages ,Hordeum ,DNA ,Molecular biology ,Amino acid ,Thionin ,chemistry ,Protein Biosynthesis ,Mutation ,Edible Grain ,Ribosomes ,Antimicrobial Cationic Peptides - Abstract
A cDNA library, prepared from developing barley endosperm, was screened for thionin recombinants. Clone pTH1 was that with the largest insert out of three identified. The longest reading frame in the 610-base-pair insert codes for a protein of 127 amino acids that includes an internal sequence of 45 amino acids, which is identical to that obtained for the alpha-hordothionin by direct protein sequencing. The deduced thionin sequence is preceded by a leader sequence of 18 residues and followed by a sequence that corresponds to an acidic protein of 64 amino acids. This structure supports previous evidence indicating that thionin is synthesized as a much larger precursor, which undergoes two processing steps: the cotranslational cleavage of a leader sequence and the post-translational one of a larger peptide. The size of the mRNA was estimated to be about 950 bases by Northern analysis. Thionin concentration in mature endosperm of barley cv. Bomi was about twice that of its high-lysine mutant Risø 1508. The same difference was observed in thionin mRNA in the corresponding developing endosperms, indicating that gene expression is partially blocked in the mutant at a pretranslational level.
- Published
- 1986
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