Isolation of a new cardiotoxic protein from the edible mushroom, Volvariella volvacea

Pore-Forming Cardiotoxin VVA2 (Volvatoxin A2) Variant I82E/L86K Is an Atypical Duplex-Specific Nuclease

VVA2 (volvatoxin A chain 2) is a cardiotoxic protein purified from Volvariella volvacea. Its biological activities include hemolysis, writhing reaction, neurotoxicity, and ventricular systolic arresting activity. The cytotoxicity of VVA2 was mainly considered due to its pore-forming activity. Here we report a novel biological activity of its variants VVA2 I82E/K86K as a duplex-specific nuclease. Recombinant VVA2 variant I82E/L86K (Re-VVA2 I82E/L86K), deprived of the oligomerization property, shows increased nuclease activity compared to VVA2. Re-VVA2 I82E/L86K converts supercoiled DNA (Replicative form I, RF I) into nicked form (RF II) and linear form (RF III) in the presence of Mg²⁺ or Mn²⁺. Besides plasmid DNA, it also exhibits nuclease activity on E. coli genomic DNA rather than ssDNA or RNA. Re-VVA2 I82E/L86K preferentially cleaves dG-dC-rich dsDNA regions and shows the best performance at pH 6–9 and 55 °C. Our structure–function study has revealed amino acid E111 may take an active part in nuclease activity through interacting with metal ions. Based on the sequences of its cleavage sites, a “double-hit” mechanism was thereby proposed. Given that Re-VVA2 I82E/L86K did not exhibit the conserved nuclease structure and sequence, it is considered an atypical duplex-specific nuclease.

The Cytocidal Spectrum of Bacillus thuringiensis Toxins: From Insects to Human Cancer Cells

Bacillus thuringiensis (Bt) is a ubiquitous bacterium in soils, insect cadavers, phylloplane, water, and stored grain, that produces several proteins, each one toxic to different biological targets such as insects, nematodes, mites, protozoa, and mammalian cells. Most Bt toxins identify their particular target through the recognition of specific cell membrane receptors. Cry proteins are the best-known toxins from Bt and a great amount of research has been published. Cry are cytotoxic to insect larvae that affect important crops recognizing specific cell membrane receptors such as cadherin, aminopeptidase-N, and alkaline phosphatase. Furthermore, some Cry toxins such as Cry4A, Cry4B, and Cry11A act synergistically with Cyt toxins against dipteran larvae vectors of human disease. Research developed with Cry proteins revealed that these toxins also could kill human cancer cells through the interaction with specific receptors. Parasporins are a small group of patented toxins that may or may not have insecticidal activity. These proteins could kill a wide variety of mammalian cancer cells by recognizing specific membrane receptors, just like Cry toxins do. Surface layer proteins (SLP), unlike the other proteins produced by Bt, are also produced by most bacteria and archaebacteria. It was recently demonstrated that SLP produced by Bt could interact with membrane receptors of insect and human cancer cells to kill them. Cyt toxins have a structure that is mostly unrelated to Cry toxins; thereby, other mechanisms of action have been reported to them. These toxins affect mainly mosquitoes that are vectors of human diseases like Anopheles spp (malaria), Aedes spp (dengue, zika, and chikungunya), and Culex spp (Nile fever and Rift Valley fever), respectively. In addition to the Cry, Cyt, and parasporins toxins produced during spore formation as inclusion bodies, Bt strains also produce Vip (Vegetative insecticidal toxins) and Sip (Secreted insecticidal proteins) toxins with insecticidal activity during their vegetative growth phase.

Up-regulation of carbon metabolism-related glyoxylate cycle and toxin production in Beauveria bassiana JEF-007 during infection of bean bug, Riptortus pedestris (Hemiptera: Alydidae)

Beauveria bassiana (Bb) is used as an environment-friendly biopesticide. However, the molecular mechanisms of Bb-host interactions are not well understood. Herein, RNA isolated from B. bassiana (Bb JEF-007) and Riptortus pedestris (Hemiptera: Alydidae) infected with this strain were firstly subjected to high-throughput next generation sequencing (NGS) to analyze and compare transcriptomes. Due to lack of fungal and host genome information, fungal transcriptome was processed to partially exclude non-infection specific genes and host-flora. Differentially Expressed Gene (DEG) analysis showed that 2381 genes were up-regulated and 2303 genes were down-regulated upon infection. Most DEGs were classified into the categories of single-organism, cellular and metabolism processes by Gene Ontology analysis. Most DEGs were involved in metabolic pathways based on Kyoto Encyclopedia of Genes and Genomes pathway mapping. Carbon metabolism-related enzymes in the glyoxylate cycle were significantly up-regulated, suggesting a possible role for them in Bb growth in the host. Additionally, transcript levels of several fungal genes were dramatically increased after infection, such as cytotoxic lectin-like protein, bacterial-like toxin, proteins related to cell wall formation, hyphal growth, nutrient uptake, and halogenated compound synthesis. This work provides insight into how entomopathogenic B. bassiana grows in agriculturally harmful bean bug at 6 d post infection.

Structural insights into Bacillus thuringiensis Cry, Cyt and parasporin toxins

Since the first X-ray structure of Cry3Aa was revealed in 1991, numerous structures of B. thuringiensis toxins have been determined and published. In recent years, functional studies on the mode of action and resistance mechanism have been proposed, which notably promoted the developments of biological insecticides and insect-resistant transgenic crops. With the exploration of known pore-forming toxins (PFTs) structures, similarities between PFTs and B. thuringiensis toxins have provided great insights into receptor binding interactions and conformational changes from water-soluble to membrane pore-forming state of B. thuringiensis toxins. This review mainly focuses on the latest discoveries of the toxin working mechanism, with the emphasis on structural related progress. Based on the structural features, B. thuringiensis Cry, Cyt and parasporin toxins could be divided into three categories: three-domain type α-PFTs, Cyt toxin type β-PFTs and aerolysin type β-PFTs. Structures from each group are elucidated and discussed in relation to the latest data, respectively.

Fungal hemolysins

Hemolysins are a class of proteins defined by their ability to lyse red cells but have been described to exhibit pleiotropic functions. These proteins have been extensively studied in bacteria and more recently in fungi. Within the last decade, a number of studies have characterized fungal hemolysins and revealed a fascinating yet diverse group of proteins. The purpose of this review is to provide a synopsis of the known fungal hemolysins with an emphasis on those belonging to the aegerolysin protein family. New insight and perspective into fungal hemolysins in biotechnology and health are additionally presented.

High-resolution crystal structure of activated Cyt2Ba monomer from Bacillus thuringiensis subsp. israelensis

The Cyt family of proteins consists of delta-endotoxins expressed during sporulation of several subspecies of Bacillus thuringiensis. Its members possess insecticidal, hemolytic, and cytolytic activities through pore formation and attract attention due to their potential use as vehicles for targeted membrane destruction. The delta-endotoxins of subsp. israelensis include three Cyt species: a major Cyt1Aa and two minor proteins, Cyt2Ba and Cyt1Ca. A cleaved Cyt protein that lacks the N- and C-terminal segments forms a toxic monomer. Here, we describe the crystal structure of Cyt2Ba, cleaved at its amino and carboxy termini by bacterial endogenous protease(s). Overall, its fold resembles that of the previously described volvatoxin A2 and the nontoxic form of Cyt2Aa. The structural similarity between these three proteins may provide information regarding the mechanism(s) of membrane-perforating toxins.

Inhibitory effects of nontoxic protein volvatoxin A1 on pore-forming cardiotoxic protein volvatoxin A2 by interaction with amphipathic alpha-helix

Volvatoxin A2, a pore-forming cardiotoxic protein, was isolated from the edible mushroom Volvariella volvacea. Previous studies have demonstrated that volvatoxin A consists of volvatoxin A2 and volvatoxin A1, and the hemolytic activity of volvatoxin A2 is completely abolished by volvatoxin A1 at a volvatoxin A2/volvatoxin A1 molar ratio of 2. In this study, we investigated the molecular mechanism by which volvatoxin A1 inhibits the cytotoxicity of volvatoxin A2. Volvatoxin A1 by itself was found to be nontoxic, and furthermore, it inhibited the hemolytic and cytotoxic activities of volvatoxin A2 at molar ratios of 2 or lower. Interestingly, volvatoxin A1 contains 393 amino acid residues that closely resemble a tandem repeat of volvatoxin A2. Volvatoxin A1 contains two pairs of amphipathic alpha-helices but it lacks a heparin-binding site. This suggests that volvatoxin A1 may interact with volvatoxin A2 but not with the cell membrane. By using confocal microscopy, it was demonstrated that volvatoxin A1 could not bind to the cell membrane; however, volvatoxin A1 could inhibit binding of volvatoxin A2 to the cell membrane at a molar ratio of 2. Via peptide competition assay and in conjunction with pull-down and co-pull-down experiments, we demonstrated that volvatoxin A1 and volvatoxin A2 may form a complex. Our results suggest that this occurs via the interaction of one molecule of volvatoxin A1, which contains two amphipathic alpha-helices, with two molecules of volvatoxin A2, each of which contains one amphipathic alpha-helix. Taken together, the results of this study reveal a novel mechanism by which volvatoxin A1 regulates the cytotoxicity of volvatoxin A2 via direct interaction, and potentially provide an exciting new strategy for chemotherapy.

Crystal structures and electron micrographs of fungal volvatoxin A2

Membrane adhesion and insertion of protein are essential to all organisms, but the underlying mechanisms remain largely unknown. Membrane pore-forming toxins (PFTs) are potential model systems for studying these mechanisms. We have determined the crystal structures of volvatoxin A2 (VVA2), a fungal PFT from Volvariella volvacea, using Br-multiple-wavelength anomalous diffraction (MAD). The VVA2 structures obtained at pH 4.6, pH 5.5 and pH 6.5 were refined to resolutions of 1.42 A, 2.6 A and 3.2 A, respectively. The structures reveal that the VVA2 monomer contains a single alpha/beta domain. Most of the VVA2 surface is occupied by its oligomerization motif and two putative heparin-binding motifs. Residues Ala91 to Ala101 display several conformations at different pH values, which might be under the control of His87. We also found that the shape of one putative heparin-binding motif in VVA2 appears similar to those found in fibroblast growth factors, and the other one displays a linear polypeptide. Our results suggest several possible intermediates of protein assembly in solution and protein adhering to cell membranes before conformational changes. The electron micrographs of VVA2 molecules in solution, at a protein concentration of 1 microg ml(-1), show that they can assemble into filament-like or braid-like oligomers in a pH-dependent way. In addition, the arc-shaped VVA2 structure obtained at pH 6.5 suggests that VVA2 could form a two-layered helical oligomer with 18 subunits per turn. The structures presented here could be used to elucidate the pore-formation mechanisms of VVA2 and its structural neighbors, Cyt toxins from Bacillus thuringiensis.

Functional domains of a pore-forming cardiotoxic protein, volvatoxin A2

Volvatoxin A2 (VVA2), a novel pore-forming cardiotoxic protein was isolated from the mushroom Volvariella volvacea. We identified an N-terminal fragment (NTF) (1-127 residues) of VVA2 as a domain for oligomerization by limited tryptic digestion. On preincubation of NTF with VVA2, NTF was found to inhibit VVA2 hemolytic activity by inducing VVA2 oligomerization in the solution in the same manner as liposomes. By site-directed mutagenesis, the amphipathic alpha-helix B of NTF or VVA2 was shown to be indispensable for its biological functions. Interestingly, at a molar ratio of recombinant NTF (reNTF)/VVA2 as low as 0.01, reNTF was able to inhibit VVA2 hemolytic activity and induce VVA2 oligomerization. This indicates that reNTF can trigger VVA2 oligomerization by a seeding effect. Furthermore, the recombinant C-terminal fragment (128-199 residues) was found to be a functional domain that mediates the membrane binding of VVA2. We found a fragment localized at the C-terminal half of VVA2 containing beta6, -7, and -8, which is protected from protease digestion because of its insertion of a membrane. We also identified a putative heparin binding site (HBS) located in the VVA2 C terminus (166-194 residues), which was conserved among 10 kinds of snake venom cardiotoxins. VVA2 or the reHBS fragment was shown to interact with sulfated glycoaminoglycans by affinity column chromatography. The finding of a higher number of glycoaminoglycans in the membrane of cardiac myocytes suggested that they could be the specific membrane target for VVA2. Taken together, these findings indicate that VVA2 contains two functional domains, NTF and CTF. The NTF domain is responsible for VVA2 oligomerization and the CTF domain for membrane binding and insertion. Our results support a model whereby the formation of VVA2 oligomeric pre-pore complexes precedes their membrane insertion.

Pleurotus and Agrocybe hemolysins, new proteins hypothetically involved in fungal fruiting

Novel hemolytic proteins, ostreolysin and aegerolysin, were purified from the fruiting bodies of the edible mushrooms Pleurotus ostreatus and Agrocybe aegerita. Both ostreolysin and aegerolysin have a molecular weight of about 16 kDa, have low isoelectric points of 5.0 and 4.85, are thermolabile, and hemolytic to bovine erythrocytes at nanomolar concentrations. Their activity is impaired by micromolar Hg(2+) but not by membrane lipids and serum low-density lipoproteins (LDL). The sequence of respectively 50 and 10 N-terminal amino acid residues of ostreolysin and aegerolysin has been determined and found to be highly identical with a cDNA-derived amino acid sequence of putative Aa-Pri1 protein from the mushroom A. aegerita, Asp-hemolysin from Aspergillus fumigatus, and two bacterial hemolysin-like proteins expressed during sporulation. We found that ostreolysin is expressed during formation of primordia and fruiting bodies, which is in accord with previous finding that the Aa-Pri1 gene is specifically expressed during fruiting initiation. It is suggestive that the isolated hemolysins play an important role in initial phase of fungal fruiting.

Assembly of flammutoxin, a cytolytic protein from the edible mushroom Flammulina velutipes, into a pore-forming ring-shaped oligomer on the target cell

Flammutoxin has been previously isolated as a cardiotoxic and cytolytic polypeptide of 22 or 32 kDa from the fruiting bodies of the edible mushroom Flammulina velutipes. In the present study, we purified flammutoxin as a single haemolytic protein of 31 kDa and studied the mode of its cytolytic action. (1) Flammutoxin caused efflux of potassium ions from human erythrocytes and swelling of the cells before haemolysis. (2) Flammutoxin did not lyse human erythrocytes in the presence of non-electrolytes with hydrodynamic diameters of >5.0 nm, although it caused leakage of potassium ions and swelling of the cells under the same conditions. (3) Experiments including solubilization of cell-bound toxin with 2% (w/v) SDS at 20 degrees C and subsequent Western immunoblots showed that flammutoxin formed a band corresponding to 180 kDa under the conditions where it lysed erythrocytes. (4) Electron microscopy of flammutoxin-treated human erythrocytes revealed the presence of a ring-shaped structure with outer and inner diameters of 10 and 5 nm, respectively, on the cells. (5) A ring-shaped toxin oligomer of the same dimensions was solubilized from the toxin-treated human erythrocytes with 2% (w/v) SDS at 20 degrees C and isolated by a sucrose-gradient ultracentrifugation. These data indicated that flammutoxin assembles into a ring-shaped oligomer possessing a hydrophilic pore of 4-5 nm on target cells.

Crystallization and preliminary x-ray analysis of volvatoxin A2 from Volvariella volvacea

Volvatoxin A2, an ion channel disturbed cardiotoxic and hemolytic protein from the edible mushroom, Volvarilla volvacea, has been crystallized by the vapor diffusion method using polyethylene glycol 4000 and ammonium sulfate in sodium acetate buffer pH 4.6. The best crystals belong to the monoclinic space group C2 with unit cell dimensions a = 155.25 angstroms, b = 58.06 angstroms, c = 116.92 angstroms, and beta = 119.5 degrees. These crystals diffract to at least 2.2 angstroms and there are four molecules of molecular weight 24 kDa per asymmetric unit with a solvent content of 48%.

Purification and some properties of a hemolysin from the poisonous mushroom Rhodophyllus rhodopolius

A hemolytic protein which causes diarrhea and death to mice was purified from the fruit bodies of a poisonous mushroom species Rhodophyllus rhodopolius (Fries) by DEAE-cellulose column chromatography, ammonium sulfate precipitation, gel filtration on Sephadex G-200, and DEAE-Sephadex A-25 column chromatography. The mol. wt of the purified hemolysin was estimated to be 40,000 by SDS-polyacrylamide slab gel electrophoresis. The hemolytic activity of the purified hemolysin was destroyed by heating at 60 degrees C for 10 min, and partially reduced by pepsin, papain and 2-mercaptoethanol. Cholesterol and phosphatidylcholine did not inhibit the activity. The hemolysin was unstable below pH 7.0 but stable at pH 8.0. The optimal pH for hemolysis was 6.0. Hemolysis did not occur below 4 degrees C even though the hemolysin bound to the erythrocyte. Mouse, chicken, rat, horse and human erythrocytes were sensitive in this order, but sheep and cow erythrocytes were not lysed by the toxin.

Pleurotus mushrooms. Part II. Chemical composition, nutritional value, post-harvest physiology, preservation, and role as human food

The fruit bodies of Pleurotus species as a class of "Edible Fungal Foods" have been discovered to have definite nutritive and medicinal values. They are a good source of nonstarchy carbohydrates, dietary fiber (that can help in reducing the plasma cholesterol), most of the essential amino acids, minerals and vitamins of B group, and folic acid (necessary to counteract pernicious anaemia) in particular. Considering the essential amino acid index, biological value, in vitro digestibility, nutritional index, and protein score, Pleurotus species fall between high grade vegetables and low grade meats. Fractions of water-soluble polysaccharides are reported to possess antitumor activity. The physiological processes such as changes in water content, respiratory rate, texture, color, and activities of enzymes like proteases and polyphenol oxidases during the after-harvest life are delineated. The problems and prospects of processing the fruit bodies by various methods are discussed. Potentialities for production and consumption of the fruit bodies in different parts of the world are brought out.

Some properties of flammutoxin from the edible mushroom Flammulina velutipes

A cytolytic toxin from the basidiocarps of the edible mushroom Flammulina velutipes was purified to homogeneity. The lysin, flammutoxin, is a single polypeptide chain of Mr 32,000 and pK about 5.4. It contains unusually large amounts of tryptophan, serine and glycine, and few or none of the sulfur-containing amino acids. Erythrocytes of rat, rabbit, guinea pig, man, mouse, cat and dog were sensitive to lysis, in that order, whereas erythrocytes of sheep, ox, goat, swine and horse were largely or completely resistant to lysis. The toxin appears not to be a phospholipase and it was not inhibitable by any of a variety of lipids. Hemolysis probably involves alteration of the erythrocyte membrane, with formation of submicroscopic ion channels, and it appears to be of the osmotic type. In some respects flammutoxin resembles phallolysin, a cytolytic toxin obtained from the mushroom Amanita phalloides.

Interactions between membranes and cytolytic peptides

The physico-chemical and biological properties of cytolytic peptides derived from diverse living entities have been discussed. The principal sources of these agents are bacteria, higher fungi, cnidarians (coelenterates) and the venoms of snakes, insects and other arthropods. Attention has been directed to instances in which cytolytic peptides obtained from phylogenetically remote as well as from related sources show similarities in nature and/or mode of action (congeneric lysins). The manner in which cytolytic peptides interact with plasma membranes of eukaryotic cells, particularly the membranes of erythrocytes, has been discussed with emphasis on melittin, thiolactivated lysins and staphylococcal alpha-toxin. These and other lytic peptides are characterized in Table III. They can be broadly categorized into: (a) those which alter permeability to allow passage of ions, this process eventuating in colloid osmotic lysis, signs of which are a pre-lytic induction or latent period, pre-lytic leakage of potassium ions, cell swelling and inhibition of lysis by sucrose. Examples of lysins in which this mechanism is involved are staphylococcal alpha-toxin, streptolysin S and aerolysin; (b) phospholipases causing enzymic degradation of bilayer phospholipids as exemplified by phospholipases C of Cl. perfringens and certain other bacteria; (c) channel-forming agents such as helianthin, gramicidin and (probably) staphylococcal delta-toxin in which toxin molecules are thought to embed themselves in the membrane to form oligomeric transmembrane channels.

A study on the interaction of crotapotin with crotoxin phospholipase A2, notexin and other presynaptic neurotoxins

1 Crotapotin, the acidic subunit of crotoxin, greatly potentiated the presynaptic effect of isolated basic phospholipase A (PLA) of crotoxin in both mouse diaphragm and chick biventer cervicis muscles whereas the myotoxic effect was not affected significantly.2 In contrast to crotoxin PLA, the presynaptic effects of notexin and notechis-5, self-active single chain toxins, were antagonized by crotapotin while actions of beta-bungarotoxin were not affected.3 By assaying PLA activity, crotoxin PLA was found to be unstable in physiological salt solution, especially when in contact with muscle, due to massive non-specific binding to and destruction by the muscle.4 The decline of crotoxin PLA was greatly reduced by the presence of crotapotin but not by another acidic protein, volvatoxin A(2), or heparin.5 Notechis-5 was found to be stable even when in the presence of muscles.6 [(3)H]-acetylated crotoxin PLA, which retained about 40% of its original enzyme and presynaptic blocking activities, also bound rapidly to the mouse diaphragm on incubation and this binding was greatly hindered by the simultaneous addition of crotapotin.7 The prevention of binding of crotoxin PLA by crotapotin occurred mostly at those sites where the binding was easily dissociable on washing. No antagonism of binding occurred at the firmly binding site.8 The binding of [(3)H]-acetylated crotapotin was much less than that of crotoxin PLA, and interestingly, the binding was increased by the latter, suggesting that crotapotin may be first bound to the diaphragm together with crotoxin PLA.9 No specific binding at the endplate zone was found either for crotoxin PLA or for crotapotin.10 It is concluded that crotapotin potentiates the presynaptic effect of crotoxin PLA by curtailing its non-specific affinity with muscles, minimizing its dispersal and destruction en route to the nerve terminal, but not by acting as an affinity probe for the nerve terminal.

A cytolytic protein from the edible mushroom, Pleurotus ostreatus

Aqueous extracts of the edible mushroom, Pleurotus ostreatus, contain a substance that is lytic in vitro for mammalian erythrocytes. The hemolytic agent, pleurotolysin, was purified to homogeneity and found to be a protein lacking seven of the amino acids commonly found in proteins. In the presence of sodium dodecyl sulfate it exists a monomers of molecular weight 12 050 whereas under non-dissociating conditions it appears to exist as dimers. It is isoelectric at about pH 6.4. The sensitivity of erythrocytes from different animals correlates with sphingomyelin content of the erythrocyte membranes. Sheep erythrocyte membranes inhibit pleurotolysin-induced hemolysis and the inhibition is time and temperature dependent. Ability of membranes to inhibit hemolysis is abolished by prior treatment of membranes with specific phospholipases. Pleurotolysin-induced hemolysis is inhibited by liposomes prepared from cholesterol, dicetyl phosphate and sphingomyelin derived from sheep erythrocytes whereas a variety of other lipid preparations fail to inhibit. It is concluded that sphingomyelin plays a key role in the hemolytic reaction.

Fungal toxins as a parasitic factor responsible for the establishment of fungal infections

Although the mechanism of fungal infections, particularly that of opportunistic fungus infections, has been studied extensively, much still remains to be clarified. As is the case of certain bacterial infections, it has long been assumed by numerous investigators that some toxins, enzymes and other metabolites produced in vitro as well as in vivo by pathogenic fungi or their cellular constituents might be responsible for the establishment of fungal infections. However, there are very few papers which deal with isolation and/or characterization of pathogenic fungus-derived toxins, particularly those of high molecular weight, to sufficiently meet various criteria for toxins including etiopathological ability. Likewise, it has been speculated that certain enzymes produced by pathogenic fungi are related to the pathogenesis of infections with the fungi implicated, but no direct evidence has been provided. It is commonly held by researchers concerned with medical mycology that the lowering of specific and/or nonspecific resistance of a host to pathogenic fungi is a prerequisite for the establishment of infections, particularly opportunistic infections. However, it is also accepted that if a given fungus possesses no parasite factors (e.g. toxigenicity, invasiveness and others), it would be unable to initiate infection even when the host is in a severe immunodeficient state. This is supported by our recent studies working with Saccharomyces cerevisiae and some other so-called nonpathogenic yeasts (unpublished data). Based on these considerations, the author and his co-workers have attempted to isolate several high and low molecular weight toxins in a pure state from virulent strains of Candida albicans and Aspergillus fumigatus as opportunist. Studies have also been made on the etiopathological roles of some successfully isolated toxins in infections with the fungi implicated (46). In addition to our experimental results, general concepts in fungal toxins, particularly those related to such toxins as isolated in our laboratory are outlined. Since opportunistic fungus infections have created a global problem because of their world-wide prevalence, a sharp demarcation between the so-called pathogenic and nonpathogenic fungi has become vague. Despite this situation, two terms are conventionally used throughout this paper.

Amatoxins, phallotoxins, phallolysin, and antamanide: the biologically active components of poisonous Amanita mushrooms

This review gives a comprehensive account of the molecular toxicology of the bicyclic peptides obtained from the poisonous mushrooms of the genus Amanita. The discussion of the biochemical events will be preceded by a consideration of the chemistry of the toxic peptides. The structural features essential for biological activities of both the amatoxins and the phallotoxins will be discussed, also including the most important analytical data. Similar consideration will be given to antamanide, a cyclic peptide, which counteracts phalloidin. In addition, the phallolysins, three cytolytic proteins from Amanita phalloides will be discussed. The report on the biological activity of the amatoxins will deal with the sensitivity of the different RNA-polymerases towards the toxins and with their action on various cell types. Consideration will also be given to systems in which alpha-amanitin was used and can be used as a molecular tool; in the past, many investigators used the inhibitor in molecular biology, genetics, and even in physiological research. As for the phallotoxins, discussion of the affinity of these toxins for actin is provied. Further discussion attempts to understand the course of intoxication by filling in the gap between the first molecular event, formation of microfilaments, and the various lesions in hepatocytes during the intoxication.

The action of a toxin from the sea anemone Anemonia sulcata upon Mammalian heart muscles

The cardiac activity of toxin II, a basic polypeptide (m.w.: 4770) from the sea anemone Anemonia sulcata, was investigated in isolated electrically driven guinea-pig and rat auricles, Langendorff heart preparations of guinea-pigs and cat heart-lung preparations. Low concentrations of toxin II (2-100 nM) evoked a dose-dependent positive inotropic effect in the three different heart muscle preparations investigated. Higher concentrations of toxin II produced toxic symptoms like contracture and arrhythmia in auricles and atria (about 25 nM). In isolated cat hearts high toxin II concentrations (about 160 nM) caused unusual toxic symptoms such as long periods of ventricular fibrillation alternating with periods of normal cardiac activity. In rat and guinea-pig auricles as well as in Langendorff hearts of guinea-pigs the extent and rate of the positive inotropic effect induced by toxin II depended on the extracellular calcium concentration (0.45 to 2.7 mM). Toxin II did not alter the heart rate in spontaneously beating isolated cat hearts. In electrically driven guinea-pig auricles, the rate of the inotropic effect induced by toxin II was accelerated by increasing stimulation frequencies. Toxin II did not change the coronary flow in Langendorff heart preparations of guinea-pigs.

Toxic effects of phallolysin from amanita phalloides

Phallolysin, a protein from Amanita phalloides with cytolytic effects in vitro, was highly toxic when given intravenously to rats, mice, rabbits and guinea pigs: i.v. LD50 in rats was 85 Haemolytic Units (HU)/kg, corresponding to 0.05 mg protein/kg b.w. Death ensued from intravascular haemolysis. In rats large doses (600 HU/kg b.w.) caused cardiac death within a few minutes due to liberation of potassium from lysed cells. The serum contained lethal concentrations of potassium. There was also histological evidence of severe renal damage as a result of the haemolysis. In addition, phallolysin directly damaged the isolated guinea pig heart and the isolated rat liver, probably by its action on membranes. Given by mouth, phallolysin was not poisonous to rats.