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Heike Dörnenburg - One of the best experts on this subject based on the ideXlab platform.
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Plant cell culture technology–harnessing a biological approach for competitive cyclotides production
Biotechnology Letters, 2008Co-Authors: Heike DörnenburgAbstract:Cyclotides are Naturally occurring mini-proteins that have a cyclic backbone and a knotted arrangement of three disulfide bonds. They are remarkably stable and have a diverse range of therapeutically useful biological activities, including antimicrobial and anti-HIV activity, although their Natural Function appears to be plant defence agents. Cyclotides are amenable to chemical synthesis; however currently most bioactivity studies have involved the use of peptides extracted from plants. Plant cell culture technology shows promise towards the goal of producing therapeutically active cyclotides in qualities and quantities required for drug development.
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Formation of cyclotides and variations in cyclotide expression in Oldenlandia affinis suspension cultures
Applied Microbiology and Biotechnology, 2007Co-Authors: Peter Seydel, David J. Craik, Christian W. Gruber, Heike DörnenburgAbstract:Cyclotides, a family of disulfide-rich mini-proteins, show a wide range of biological activities, making them interesting targets for pharmaceutical and agrochemical applications, but little is known about their Natural Function and the events that trigger their expression. An investigation of nutritional variations and irradiation during a batch process involving plant cell cultures has been performed, using the native African medical herb, Oldenlandia affinis , as a model plant. The results demonstrated the biosynthesis of kalata B1, the main cyclotide in O. affinis , in a combined growth/nongrowth-associated pattern. The highest concentration, 0.37 mg g^−1 dry weight, was accumulated in irradiated cells at 35 μmol m^−2 s^−1. Furthermore, 12 novel cyclotides were identified and the expression of various cyclotides compared in irradiated vs non-irradiated cultures. The results indicate that cyclotide expression varies greatly depending on physiological conditions and environmental stress. Kalata B1 is the most abundant cyclotide in plant suspension cultures, which underlies its importance as a Natural defense molecule. The identification of novel cyclotides in suspension cultures, compared to whole plants, indicates that there may be more novel cyclotides to be discovered and that the genetic network regulating cyclotide expression is a very sensitive system, ready to adapt to the current environmental growth condition.
David J. Craik - One of the best experts on this subject based on the ideXlab platform.
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Discovery, structure, Function, and applications of cyclotides: circular proteins from plants
Journal of Experimental Botany, 2016Co-Authors: Joachim Weidmann, David J. CraikAbstract:Cyclotides are plant-derived cyclic peptides that have a head-to-tail cyclic backbone and three conserved disulphide bonds that form a cyclic cystine knot motif. They occur in plants from the Violaceae, Rubiaceae, Cucurbitaceae, Fabaceae, and Solanaceae families, typically with 10-100 cyclotides in a given plant species, in a wide range of tissues, including flowers, leaves, stems, and roots. Some cyclotides are expressed in large amounts (up to 1g kg wet plant weight) and their Natural Function appears to be to protect plants from pests or pathogens. This article provides a brief overview of their discovery, distribution in plants, and applications. In particular, their exceptional stability has led to their use as peptide-based scaffolds in drug design applications. They also have potential as Natural 'ecofriendly' insecticides, and as protein engineering frameworks.
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Cyclotide isolation and characterization.
Methods in Enzymology, 2012Co-Authors: David J. Craik, Sónia Troeira Henriques, Joshua S. Mylne, Conan K. WangAbstract:Cyclotides are disulfide-rich cyclic peptides produced by plants with the presumed Natural Function of defense agents against insect pests. They are present in a wide range of plant tissues, being ribosomally synthesized via precursor proteins that are posttranslationally processed to produce mature peptides with a characteristic cyclic backbone and cystine knot motif associated with their six conserved cysteine residues. Their processing is not fully understood but involves asparaginyl endoproteinase activity. In addition to interest in their defense roles and their unique topologies, cyclotides have attracted attention as potential templates in peptide-based drug design applications. This chapter provides protocols for the isolation of cyclotides from plants, their detection and sequencing by mass spectrometry, and their structural analysis by NMR, as well as describing methods for the isolation of nucleic acid sequences that encode their precursor proteins. Assays to assess their membrane-binding interactions are also described. These protocols provide a “starter kit” for researchers entering the cyclotide field.
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Formation of cyclotides and variations in cyclotide expression in Oldenlandia affinis suspension cultures
Applied Microbiology and Biotechnology, 2007Co-Authors: Peter Seydel, David J. Craik, Christian W. Gruber, Heike DörnenburgAbstract:Cyclotides, a family of disulfide-rich mini-proteins, show a wide range of biological activities, making them interesting targets for pharmaceutical and agrochemical applications, but little is known about their Natural Function and the events that trigger their expression. An investigation of nutritional variations and irradiation during a batch process involving plant cell cultures has been performed, using the native African medical herb, Oldenlandia affinis , as a model plant. The results demonstrated the biosynthesis of kalata B1, the main cyclotide in O. affinis , in a combined growth/nongrowth-associated pattern. The highest concentration, 0.37 mg g^−1 dry weight, was accumulated in irradiated cells at 35 μmol m^−2 s^−1. Furthermore, 12 novel cyclotides were identified and the expression of various cyclotides compared in irradiated vs non-irradiated cultures. The results indicate that cyclotide expression varies greatly depending on physiological conditions and environmental stress. Kalata B1 is the most abundant cyclotide in plant suspension cultures, which underlies its importance as a Natural defense molecule. The identification of novel cyclotides in suspension cultures, compared to whole plants, indicates that there may be more novel cyclotides to be discovered and that the genetic network regulating cyclotide expression is a very sensitive system, ready to adapt to the current environmental growth condition.
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Variations in Cyclotide Expression in Viola Species
Journal of Natural Products, 2004Co-Authors: Manuela Trabi, Erika Svangård, Anders Herrmann, Per Claeson, Ulf Göransson, David J. Craik, Lars BohlinAbstract:Cyclotides, a family of approximately 50 mini-proteins isolated from various Violaceae and Rubiaceae plants, are characterized by their circular peptide backbone and six conserved cysteine residues arranged in a cystine knot motif. Cyclotides show a wide range of biological activities, making them interesting targets for both pharmaceutical and agrochemical research, but little is known about their Natural Function and the events that trigger their expression. An investigation of the geographical and seasonal variations of cyclotide profiles has been performed, using the native Australian violet, Viola hederacea, and the Swedish sweet violet, Viola odorata, as model plants. The results showed that in the Australian violet the relative peptide levels of some cyclotides remained almost constant throughout the year, while other cyclotides were present only at certain times of the year. Therefore, it appears that V. hederacea expresses a basic armory of cyclotides as well as special add-ons whose levels are influenced by external factors. In the Swedish violet, cyclotide levels were increased up to 14 times during the warmest period of the year. The larger variation in expression levels of the Swedish plants may be a reflection of a greater climatic variation.
Tamas Dalmay - One of the best experts on this subject based on the ideXlab platform.
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analysis of short rnas in the malaria parasite and its red blood cell host
FEBS Letters, 2006Co-Authors: Tina Rathjen, Clare Nicol, Glenn A Mcconkey, Tamas DalmayAbstract:RNA interference (RNAi) is an RNA degradation process that involves short, double-stranded RNAs (dsRNA) as sequence specificity factors. The Natural Function of the RNAi machinery is to generate endogenous short double-stranded RNAs to regulate gene expression. It has been shown that treatment of Plasmodium falciparum, the etiologic agent of malaria, with dsRNA induces degradation of the corresponding microRNA (miRNA), yet typical RNAi-associated genes have not been identifiable in the parasite genome. To clarify this discrepancy we set out to clone short RNAs from P. falciparum-infected red blood cells and from purified parasites. We did not find any short RNA that was not a rRNA or tRNA fragment. Indeed, only known human miRNAs were isolated in parasite preparations indicating that very few if any short RNAs exist in P. falciparum. This suggests a different mechanism than classical RNAi in observations of dsRNA-mediated degradation. Of the human miRNAs identified, the human miRNA mir-451 accumulates at a very high level in both infected and healthy red blood cells. Interestingly, mir-451 was not detectable in a series of immortalised cell lines representing progenitor stages of all major blood lineages, suggesting that mir-451 may play a role in the differentiation of erythroid cells.
Peter Seydel - One of the best experts on this subject based on the ideXlab platform.
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Formation of cyclotides and variations in cyclotide expression in Oldenlandia affinis suspension cultures
Applied Microbiology and Biotechnology, 2007Co-Authors: Peter Seydel, David J. Craik, Christian W. Gruber, Heike DörnenburgAbstract:Cyclotides, a family of disulfide-rich mini-proteins, show a wide range of biological activities, making them interesting targets for pharmaceutical and agrochemical applications, but little is known about their Natural Function and the events that trigger their expression. An investigation of nutritional variations and irradiation during a batch process involving plant cell cultures has been performed, using the native African medical herb, Oldenlandia affinis , as a model plant. The results demonstrated the biosynthesis of kalata B1, the main cyclotide in O. affinis , in a combined growth/nongrowth-associated pattern. The highest concentration, 0.37 mg g^−1 dry weight, was accumulated in irradiated cells at 35 μmol m^−2 s^−1. Furthermore, 12 novel cyclotides were identified and the expression of various cyclotides compared in irradiated vs non-irradiated cultures. The results indicate that cyclotide expression varies greatly depending on physiological conditions and environmental stress. Kalata B1 is the most abundant cyclotide in plant suspension cultures, which underlies its importance as a Natural defense molecule. The identification of novel cyclotides in suspension cultures, compared to whole plants, indicates that there may be more novel cyclotides to be discovered and that the genetic network regulating cyclotide expression is a very sensitive system, ready to adapt to the current environmental growth condition.
Christian W. Gruber - One of the best experts on this subject based on the ideXlab platform.
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Formation of cyclotides and variations in cyclotide expression in Oldenlandia affinis suspension cultures
Applied Microbiology and Biotechnology, 2007Co-Authors: Peter Seydel, David J. Craik, Christian W. Gruber, Heike DörnenburgAbstract:Cyclotides, a family of disulfide-rich mini-proteins, show a wide range of biological activities, making them interesting targets for pharmaceutical and agrochemical applications, but little is known about their Natural Function and the events that trigger their expression. An investigation of nutritional variations and irradiation during a batch process involving plant cell cultures has been performed, using the native African medical herb, Oldenlandia affinis , as a model plant. The results demonstrated the biosynthesis of kalata B1, the main cyclotide in O. affinis , in a combined growth/nongrowth-associated pattern. The highest concentration, 0.37 mg g^−1 dry weight, was accumulated in irradiated cells at 35 μmol m^−2 s^−1. Furthermore, 12 novel cyclotides were identified and the expression of various cyclotides compared in irradiated vs non-irradiated cultures. The results indicate that cyclotide expression varies greatly depending on physiological conditions and environmental stress. Kalata B1 is the most abundant cyclotide in plant suspension cultures, which underlies its importance as a Natural defense molecule. The identification of novel cyclotides in suspension cultures, compared to whole plants, indicates that there may be more novel cyclotides to be discovered and that the genetic network regulating cyclotide expression is a very sensitive system, ready to adapt to the current environmental growth condition.