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At least 127 records · Page 7Linked to original sources
PubMed1992

Sea anemone Radianthus macrodactylus--a new source of palytoxin.

A very potent non-protein toxin was isolated from the sea anemone Radianthus macrodactylus with the use of chromatography on polytetrafluoroethylene, CM-Sephadex C-25 and by cation and anion exchange HPLC. The toxin was identified as palytoxin by u.v.-, i.r.- and 500 MHz 1H NMR spectroscopy. Its LD50 was 0.74 +/- 0.29 micrograms/kg by i.v. injection into mice. So far, palytoxin has been associated with zoanthids only. The toxin caused the loss of haemoglobin from erythrocytes but only in about 2 hr after the beginning of incubation, which is characteristic for palytoxin from zoanthids. Sea anemone palytoxin was divided into major and minor components by HPLC. The latter proved to be a product of degradation of palytoxin.

Acrylamides↗
PubMed1993

Characterization of peptides in sea anemone venom collected by a novel procedure.

Peptide neurotoxins were isolated from the venom obtained by electrical stimulation of the sea anemone Bunodosoma caissarum. This technique allows almost pure venom to be collected, and the animals to survive. Three neurotoxins (assayed on crustacean nerves) were isolated by gel filtration and reversed-phase high performance liquid chromatography. Hemolysins were also detected in the venom. The amino acid sequence of a major neurotoxin BcIII was determined. BcIII has 48 amino acid residues with six half-cystine residues. This sequence has homology with the type 1 long sea anemone neurotoxins. Two minor toxins (BcI and II) have similar amino acid composition and amino-terminal sequences to BcIII.

Action Potentials↗
PubMed1995

Characterization of a potassium channel toxin from the Caribbean Sea anemone Stichodactyla helianthus.

A peptide toxin, ShK, that blocks voltage-dependent potassium channels was isolated from the whole body extract of the Caribbean sea anemone Stichodactyla helianthus. It competes with dendrotoxin I and alpha-dendrotoxin for binding to synaptosomal membranes of rat brain, facilities acetylcholine release at an avian neuromuscular junction and suppresses K+ currents in rat dorsal root ganglion neurones in culture. Its amino acid sequence is R1SCIDTIPKS10RCTAFQCKHS20MKYRLSFCRK30TCGTC35. There is no homology with other K+ channel-blocking peptides, except for BgK from the sea anemone Bunodosoma granulifera. ShK and BgK appear to be in a different structural class from other toxins affecting K+ channels.

Amino Acid Sequence↗
PubMedDate not supplied

Isolation of <Glu-Asn-Phe-His-Leu-Arg-Pro-NH2 (Antho-RPamide II), a novel, biologically active neuropeptide from sea anemones.

Using a radioimmunoassay against the C-terminal sequence Arg-Pro-NH2 (RPamide) we have isolated the neuropeptide <Glu-Asn-Phe-His-Leu-Arg-Pro-NH2 (Antho-RPamide II) from extracts of the sea anemone Anthopleura elegantissima. Addition of low concentrations of Antho-RPamide II to a tentacle preparation of sea anemones inhibited the spontaneous, rhythmic contractions, suggesting that the peptide is a neurotransmitter or neuromodulator.

Amino Acid Sequence↗
PubMed1996

The anthozoan neuropeptide Antho-RWamide I modulates Ca2+ current in sea anemone myoepithelial cells.

The anthozoan neuropeptide Antho-RWamide I (< Glu-Ser-Leu-Arg-Trp-NH2) excites contraction of endodermal muscles in sea anemones. Single electrode voltage clamp recordings from semi-intact preparations of endodermal myoepithelial cells reveal that Antho-RWamide I increases an inward Ca2+ current. Evidence for the involvement of a Ca2+ current in contraction was supported by the observation that Cd2+ abolished spontaneous contractions and reduced inward current. Contractions and inward currents induced by Antho-RWamide I were not, however, completely abolished in the presence of Cd2+. We conclude that Antho-RWamide, a putative neurotransmitter at sea anemone smooth muscle, acts by opening, either directly or indirectly, Ca2+ channels in the muscle membrane.

Animals↗
PubMed2006

Effects of ApC, a sea anemone toxin, on sodium currents of mammalian neurons.

We have characterized the actions of ApC, a sea anemone polypeptide toxin isolated from Anthopleura elegantissima, on neuronal sodium currents (I(Na)) using current and voltage-clamp techniques. Neurons of the dorsal root ganglia of Wistar rats (P5-9) in primary culture were used for this study. These cells express tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) I(Na). In current-clamp experiments, application of ApC increased the average duration of the action potential. Under voltage-clamp conditions, the main effect of ApC was a concentration-dependent increase in the TTX-S I(Na) inactivation time course. No significant effects were observed on the activation time course or on the current peak-amplitude. ApC also produced a hyperpolarizing shift in the voltage at which 50% of the channels are inactivated and caused a significant decrease in the voltage dependence of Na+ channel inactivation. No effects were observed on TTX-R I(Na). Our results suggest that ApC slows the conformational changes required for fast inactivation of the mammalian Na+ channels in a form similar to other site-3 toxins, although with a greater potency than ATX-II, a highly homologous anemone toxin.

Animals↗
PubMed2004

Molecular characterization of two CuZn-superoxide dismutases in a sea anemone.

Cnidarians living in symbiosis with photosynthetic cells--called zooxanthellae--are submitted to high oxygen levels generated by photosynthesis. To cope with this hyperoxic state, symbiotic cnidarians present a high diversity of superoxide dismutases (SOD) isoforms. To understand better the mechanism of resistance of cnidarian hosts to hyperoxia, we studied copper- and zinc-containing SOD (CuZnSOD) from Anemonia viridis, a temperate symbiotic sea anemone. We cloned two CuZnSOD genes that we call AvCuZnSODa and AvCuZnSODb. Their molecular analysis suggests that the AvCuZnSODa transcript encodes an extracellular form of CuZnSOD, whereas the AvCuZnSODb transcript encodes an intracellular form. Using in situ hybridization, we showed that both AvCuZnSODa and AvCuZnSODb transcripts are expressed in the endodermal and ectodermal cells of the sea anemone, but not in the zooxanthellae. The genomic flanking sequences of AvCuZnSODa and AvCuZnSODb revealed different putative binding sites for transcription factors, suggesting different modes of regulation for the two genes. This study represents a first step in the understanding of the molecular mechanisms of host animal resistance to permanent hyperoxia status resulting from the photosynthetic symbiosis. Moreover, AvCuZnSODa and AvCuZnSODb are the first SODs cloned from a diploblastic animal, contributing to the evolutionary understanding of SODs.

Amino Acid Sequence↗
PubMed2006

Catalase characterization and implication in bleaching of a symbiotic sea anemone.

Symbiotic cnidarians are marine invertebrates harboring photosynthesizing microalgae (named zooxanthellae), which produce great amounts of oxygen and free radicals upon illumination. Studying antioxidative balance is then crucial to understanding how symbiotic cnidarians cope with ROS production. In particular, it is suspected that oxidative stress triggers cnidarian bleaching, i.e., the expulsion of zooxanthellae from the animal host, responsible for symbiotic cnidarian mass mortality worldwide. This study therefore investigates catalase antioxidant enzymes and their role in bleaching of the temperate symbiotic sea anemone Anemonia viridis. Using specific separation of animal tissues (ectoderm and endoderm) from the symbionts (zooxanthellae), spectrophotometric assays and native PAGE revealed both tissue-specific and activity pattern distribution of two catalase electrophoretypes, E1 and E2. E1, expressed in all three tissues, presents high sensitivity to the catalase inhibitor aminotriazole (ATZ) and elevated temperatures. The ectodermal E1 form is responsible for 67% of total catalase activity. The E2 form, expressed only within zooxanthellae and their host endodermal cells, displays low sensitivity to ATZ and relative thermostability. We further cloned an ectodermal catalase, which shares 68% identity with mammalian monofunctional catalases. Last, 6 days of exposure of whole sea anemones to ATZ (0.5 mM) led to effective catalase inhibition and initiated symbiont expulsion. This demonstrates the crucial role of this enzyme in cnidarian bleaching, a phenomenon responsible for worldwide climate-change-induced mass mortalities, with catastrophic consequences for marine biodiversity.

Amino Acid Sequence↗
PubMed2006

The crude venom from the sea anemone Stichodactyla helianthus induces haemolysis and slight peroxidative damage in rat and human erythrocytes.

The haemolytic and peroxidative effects of crude venom of the sea anemone Stichodactyla helianthus were evaluated in rat and human erythrocytes. Venom extract caused a significant concentration-dependent effect on haemolysis (release of haemoglobin). Human erythrocytes were more sensitive (0.094 mg protein/ml) than those of the rats (0.3787 mg protein/ml). In contrast, a light effect on lipid peroxidation (LP, an index of oxidative damage to membrane lipids) was recorded. The concentrations needed to produce a significant effect on LP in rat and human erythrocytes were, respectively, 2-fold and 7-fold higher than those required to produce significant haemolysis. The differential effect of S. helianthus venom on haemolysis and oxidation of membrane lipids is not common for venoms of other sea anemones, which usually show a tightly related effect on LP and haemolytic damage.

Animals↗
PubMed2004

Comparison of sea anemone and scorpion toxins binding to Kv1 channels: an example of convergent evolution.

Comparison of data from functional mapping carried out on scorpion and sea anemones toxins blocking currents through voltage-gated potassium channels revealed that, despite their different 3D structures, the binding cores of these toxins displayed some similarities. Further molecular modeling studies suggested that these similarities reflect the use by these toxins of a common binding mode to exert their blocking function. Therefore, scorpion and sea anemone toxins offer an example of mechanistic convergent evolution.

Amino Acid Sequence↗
PubMed2004

Isolation, properties and partial amino acid sequence of a new actinoporin from the sea anemone Radianthus macrodactylus.

A new cytolytic toxin, actinoporin RTX-S II, was isolated from the sea anemone Radianthus macrodactylus with a high degree of purity by a combination of gel filtration, ion-exchange and reverse-phase chromatography. RTX-S II has molecular mass of 19,280 Da and isoelectric point of 10.0. The hemolytic activity of RTX-S II is inhibited by sphingomyelin. RTX-S II had an LD(50) of 70 mg/kg, and is lacking in phospholipase activity. The amino acid composition of this protein contains a high amount of basic and non-polar amino acids and no cysteine. The N-terminal sequence of RTX-S II was determined. The partial amino acid sequence (141 aa) of RTX-S II was deduced based on the cDNA sequence obtained with two oligonucleotides encoding the N-terminal portion of RTX-S II and the internal conserved cytolysin peptide by PCR. A comparison of the RTX-S II cDNA sequence and the rtx-s II gene obtained with the same PCR primers indicates that they are 100% identical at the nucleotide level. It shows that no introns are present in the corresponding region of the rtx-s II gene. Multiple alignments of RTX-S II with known sequences of actinoporins show that RTX-S II is highly homologous to magnificalysin II from Heteractis magnifica. The predicted secondary structure of RTX-S II is predominantly anti-parallel beta-structure, which is in good agreement with experimental data obtained from other sea anemones-actinoporins.

Amino Acid Sequence↗
PubMed2005

Biochemical and physiological analyses of a hemolytic toxin isolated from a sea anemone Actineria villosa.

A species of venomous sea anemone Actineria villosa was recently found inhabiting the coastal areas of Okinawa, Japan. This marine animal produces various proteinous toxins, so that a local health organization was called for medical treatment for those who had accidental contact with this animal. In this study we analyzed the biochemical and physiological properties of hemolytic protein from A. villosa. The toxin purified from the tentacles of the animals was found to be a protein with a molecular weight of approximately 19 kDa. We named this newly found hemolytic toxin of A. villosa, Avt-I. Incubation of the toxin with sphingomyelin inhibited hemolytic activity by up to 85%, showing that Avt-I may target sphingomyelin on the erythrocyte membrane. The hemolytic activity was stably maintained at temperatures below 45 degrees C, however, a sharp linear decrease in heat stability was observed within the range of 45-55 degrees C. Our results provide the first evidence that A. villosa produces a toxin with strong hemolytic activity similar in biochemical and physiological properties to other members of actinoporin family previously isolated from related species of sea anemones.

Amino Acid Sequence↗
PubMed2005

Novel peptide toxins from acrorhagi, aggressive organs of the sea anemone Actinia equina.

Two peptide toxins, acrorhagin I (50 residues) and II (44 residues), were isolated from special aggressive organs (acrorhagi) of the sea anemone Actinia equina by gel filtration on Sephadex G-50 and reverse-phase HPLC on TSKgel ODS-120T. The LD50 against crabs of acrorhagin I and II were estimated to be 520 and 80 microg/kg, respectively. 3'- and 5'-RACE established the amino acid sequences of the acrorhagin precursors. The precursor of acrorhagin I is composed of both signal and mature peptides and that of acrorhagin II has an additional sequence (propart) between signal and mature peptides. Acrorhagin I has no sequence homologies with any toxins, while acrorhagin II is somewhat similar to spider neurotoxins (hainantoxin-I from Selenocosmia hainana and Tx 3-2 from Phoneutria nigriventer) and cone snail neurotoxin (omega-conotoxin MVIIB from Conus magus). In addition, analogous peptides (acrorhagin Ia and IIa) were also cloned during RT-PCR experiments performed to confirm the nucleotide sequences of acrorhagins. This is the first to demonstrate the existence of novel peptide toxins in the sea anemone acrorhagi.

Amino Acid Sequence↗
PubMed1999

Antiparasite activity of sea-anemone cytolysins on Giardia duodenalis and specific targeting with anti-Giardia antibodies.

The killing activity of sea-anemone cytolysins on Giardia duodenalis was investigated. Three different toxins, sticholysin I and II from Stichodactyla helianthus (St I and St II) and equinatoxin II from Actinia equina (EqtII) were all found to be active in an acute test, with a C50 in the nanomolar range (St I, 0.5 nM; St II, 1.6 nM; and EqtII, 0.8 nM). A method to target the cytolysin activity more specifically towards the parasite cells by using anti-Giardia antibodies was then investigated. Parasite cells were sensitised with a primary murine monoclonal or polyclonal antibody followed by a biotinylated secondary anti-mouse-IgG monoclonal antibody. Subsequently, avidin and a biotinylated EqtII mutant were added, either in two separate steps or as a pre-formed conjugate. When the monoclonal antibody was used, the C50 of biotinylated EqtII was 1.3 nM with sensitised cells and 5 nM with non-sensitised cells, indicating a four-fold enhancement of activity with the cell treatment. Treatment with the polyclonal antibody was somehow more effective than with the monoclonal antibody in an acute test. This indicates that sea-anemone cytolysins can efficiently kill Giardia cells, and that it is possible to improve, to a certain extent, the anti-parasite specificity of these toxins with anti-Giardia antibodies. However, the feasibility of this approach "in vivo" remains to be demonstrated.

Animals↗
PubMed2001

Isolation and characterisation of five neurotoxic and cardiotoxic polypeptides from the sea anemone Anthopleura elegantissima.

Five toxins (APE 1 to APE 5) of the sea anemone species Anthopleura elegantissima (Brandt) have been isolated from a toxic by-product fraction of its concentrated crude watery-methanolic extract, prepared previously for the isolation of a neuropeptide (the head-activator) by Schaller and Bodenmüller (Proc. Natl. Acad. Sci. USA 78 (1981) 7000) from 200kg sea anemones. Toxin purification was performed by desalting of the starting material by dialysis (MWCO 3500) against distilled water, anion exchange chromatography on QAE-Sephadex A25 at pH 8, twice gel filtration on Sephadex G50 m, repeated chromatography on QAE-Sephadex at pH 10 and chromatography on the cation exchanger Fractogel EMD SO(3)(-)-650 M.Final purification of the toxins was achieved by HPLC on MN SP 250/10 Nucleosil 500-5 C(18) PPN and MN SP 250/21 Nucleosil 300-7 C(18). Each toxin was composed of at least two isotoxins of which APE 1-1, APE 1-2, APE 2-1, APE 2-2 and APE 5-3 were isolated in preparative scale. With exception of APE 5-3 the sequences of the isotoxins have been elucidated. They resemble the 47 residue type-I long polypeptide toxins native to Anemonia sulcata (Pennant). All isotoxins paralyse the shore crab (Carcinus maenas) by tetanic contractions after i.m. application. The toxins modify current passing through the fast Na(+) channel in neuroblastoma cells, leading to delayed and incomplete inactivation. APE 1-1, APE 2-1 and APE 5-3 produce a positive inotropic effect in mammalian heart muscle, although they differ in potency. The order of potency is APE 2-1>APE 1-1>APE 5-3 (i.e. threshold concentrations are 1, 10 and 300nM, respectively). In addition, they enhance the spontaneous beating frequency in isolated right atria (guinea pig). The most potent cardiotoxic isotoxin is APE 2-1, its sequence is identical with that of AP-C, a toxin isolated and characterised previously by Norton et al. (Drugs and Foods from the Sea, 1978, University of Oklahoma Press, p. 37-50).LD50 APE 2-1:1 micro g/kg b.w. C. maenas (i.m.). LD50 APE 1-1:10 microg/kg b.w. C. maenas (i. m.). LD50 APE 5-3:50 microg/kg b.w. C. maenas (i.m.).

Animals↗
PubMed2002

Cytolytic peptide and protein toxins from sea anemones (Anthozoa: Actiniaria).

More than 32 species of sea anemones have been reported to produce lethal cytolytic peptides and proteins. Based on their primary structure and functional properties, cytolysins have been classified into four polypeptide groups. Group I consists of 5-8 kDa peptides, represented by those from the sea anemones Tealia felina and Radianthus macrodactylus. These peptides form pores in phosphatidylcholine containing membranes. The most numerous is group II comprising 20 kDa basic proteins, actinoporins, isolated from several genera of the fam. Actiniidae and Stichodactylidae. Equinatoxins, sticholysins, and magnificalysins from Actinia equina, Stichodactyla helianthus, and Heteractis magnifica, respectively, have been studied mostly. They associate typically with sphingomyelin containing membranes and create cation-selective pores. The crystal structure of equinatoxin II has been determined at 1.9A resolution. Lethal 30-40 kDa cytolytic phospholipases A(2) from Aiptasia pallida (fam. Aiptasiidae) and a similar cytolysin, which is devoid of enzymatic activity, from Urticina piscivora, form group III. A thiol-activated cytolysin, metridiolysin, with a mass of 80 kDa from Metridium senile (fam. Metridiidae) is a single representative of the fourth family. Its activity is inhibited by cholesterol or phosphatides. Biological, structure-function, and pharmacological characteristics of these cytolysins are reviewed.

Amino Acid Sequence↗
PubMed2003

An epidermal growth factor-like toxin and two sodium channel toxins from the sea anemone Stichodactyla gigantea.

Three peptide toxins (gigantoxins I-III) with crab toxicity were isolated from the sea anemone Stichodactyla gigantea by gel filtration on Sephadex G-50 and reverse-phase HPLC on TSKgel ODS-120T and their complete amino acid sequences were determined. Gigantoxins II (44 residues) and III (48 residues) have LD(50) (against crabs) of 70 and 120 microg/kg, respectively, and are analogous to the known type 1 and 2 sea anemone sodium channel toxins, respectively. On the other hand, gigantoxin I (48 residues) is potently paralytic to crabs (ED(50) 215 microg/kg), although its lethality is very weak (LD(50)>1000 microg/kg). Interestingly, gigantoxin I has 31-33% homologies with mammalian epidermal growth factors (EGFs), with the same location of six cysteine residues. In accordance with the sequence similarity, gigantoxin I exhibits EGF activity as evidenced by rounding of A431 cells and tyrosine phosphorylation of the EGF receptor in the cells, although much less potently than human EGF. Gigantoxin I is the first example of EGF-like toxins of natural origin.

Amino Acid Sequence↗
PubMed1997

Halcurin, a polypeptide toxin from the sea anemone Halcurias sp., with a structural resemblance to type 1 and 2 toxins.

The aqueous extract of the sea anemone Halcurias sp. belonging to the suborder Endocoelantheae was found to be potently lethal to crabs, although it showed neither lethal activity in mice nor hemolytic activity. A polypeptide toxin (named halcurin) with a LD50 of 5.8 micrograms/kg against crabs was isolated by gel filtration on Sephadex G-50 and reverse-phase high-performance liquid chromatography on TSKgel ODS-120T. The complete amino acid sequence of halcurin comprising 47 residues was elucidated by sequence analysis of the native molecule and its enzymatic fragment. Comparison with the known sea anemone polypeptide toxins (types 1-3), which are all from members of the suborder Nynantheae, revealed a high sequence homology (49-74%) of halcurin with type 2 toxins. Also, halcurin has several residues conserved for only type 1 toxins. These results, together with the fact the Halcurias sp. is a more primitive species than members of Nynantheae, suggest that type 1 and 2 toxins have evolved from a common ancestor with a sequence more similar to halcurin.

Amino Acid Sequence↗