Functional and structural diversification of the Anguimorpha lizard venom system.

Venom has only been recently discovered to be a basal trait of the Anguimorpha lizards. Consequently, very little is known about the timings of toxin recruitment events, venom protein molecular evolution, or even the relative physical diversifications of the venom system itself. A multidisciplinary approach was used to examine the evolution across the full taxonomical range of this ∼130 million-year-old clade.

Evolution and diversification of the Toxicofera reptile venom system.

The diversification of the reptile venom system has been an area of major research but of great controversy. In this review we examine the historical and modern-day efforts of all aspects of the venom system including dentition, glands and secreted toxins and highlight areas of future research opportunities. We use multidisciplinary techniques, including magnetic resonance imaging of venom glands through to molecular phylogenetic reconstruction of toxin evolutionary history, to illustrate the diversity within this integrated weapons system and map the timing of toxin recruitment events over the toxicoferan organismal evolutionary tree.

A central role for venom in predation by Varanus komodoensis (Komodo Dragon) and the extinct giant Varanus (Megalania) priscus.

The predatory ecology of Varanus komodoensis (Komodo Dragon) has been a subject of long-standing interest and considerable conjecture. Here, we investigate the roles and potential interplay between cranial mechanics, toxic bacteria, and venom. Our analyses point to the presence of a sophisticated combined-arsenal killing apparatus.

Evolutionary origin and development of snake fangs.

Many advanced snakes use fangs-specialized teeth associated with a venom gland-to introduce venom into prey or attacker. Various front- and rear-fanged groups are recognized, according to whether their fangs are positioned anterior (for example cobras and vipers) or posterior (for example grass snakes) in the upper jaw. A fundamental controversy in snake evolution is whether or not front and rear fangs share the same evolutionary and developmental origin.

Early evolution of the venom system in lizards and snakes.

Among extant reptiles only two lineages are known to have evolved venom delivery systems, the advanced snakes and helodermatid lizards (Gila Monster and Beaded Lizard). Evolution of the venom system is thought to underlie the impressive radiation of the advanced snakes (2,500 of 3,000 snake species). In contrast, the lizard venom system is thought to be restricted to just two species and to have evolved independently from the snake venom system.

Venomous snakes of Israel: ecology and snakebite.

Ten species of venomous snakes belonging to three families occur in Israel and in Jordan, some of which may pose a serious threat to humans. Specific, local antivenins are available against only two of the species, while against others regional or European preparations are used. It is suggested that in addition to the monospecific anti-Vipera palaestinae, a polyspecific antivenin be prepared against the clinically most important venomous snakes of the region, namely, Echis coloratus, Pseudocerastes fieldi, Cerastes cerastes, Walterinnesia aegyptia, and Atractaspis engaddensis.

A snake bite by the Burrowing Asp, Atractaspis engaddensis.

During routine milking of a group of Burrowing Asps Atractaspis engaddensis, one of the authors was bitten in the index finger by one fang, as is characteristic of bites by snakes of the genus. Local effects, oedema, erythema and numbness appeared within minutes, followed by systemic effects, including general weakness, sweating, pallor, fluctuations in the level of consciousness, vomiting and watery non-bloody diarrhoea. Gross oedema of the hand developed and extended up to the forearm.

Resistance of the Egyptian mongoose to sarafotoxins.

The Egyptian mongoose (Herpestes ichneumon) is known for its resistance to viperid and elapid venoms. The current work demonstrates that it is also resistant to the venom of Atractaspis and its most toxic component, sarafotoxin-b. Intravenous administration of this toxin, at a dose of about 13 times LD100 for mice, resulted in disturbance in electrocardiograms in the mongoose, which returned to normal after several hours.

The binding site of the nicotinic acetylcholine receptor in animal species resistant to alpha-bungarotoxin.

The ligand binding site of the nicotinic acetylcholine receptor (AChR) is located in the alpha-subunit, within a small fragment containing the tandem cysteines at positions 192 and 193. We have been analyzing the binding site domain of AChRs from several animal species exhibiting various degrees of resistance to alpha-bungarotoxin (alpha-BTX). Our earlier work on the snake and mongoose AChR, both of which do not bind alpha-BTX, suggested that amino acid substitutions at positions 187, 189, and 194 of the AChR alpha-subunit are important in determining the resistance of these AChRs to alpha-BTX.

Biological activities of [Thr2]sarafotoxin-b, a synthetic analogue of sarafotoxin-b.

The 21 amino acid sarafotoxins (SRTX) c and d/e as well as endothelin-3 (ET-3) are known to be less toxic and weaker pharmacologically than the other isopeptides SRTX-a, SRTX-b and ET-1. Since SRTX-c, SRTX-d/e and ET-3 possess a Thr instead of a Ser at position 2, we investigated the possibility that this mutation could be responsible for the observed biological differences. Here we show that the synthetic [Thr2]SRTX-b has indeed a lower vasoconstriction efficacy (approximately 35%) in the rabbit aorta, but it is nearly as potent as SRTX-b in toxicity tests and in influencing contraction of the rat uterus.

Sarafotoxins and endothelins: evolution, structure and function.

The venom of the burrowing asp Atractaspis engaddensis contains several 21 amino acid residue peptides known as sarafotoxins. The sarafotoxins are homologous to the mammalian endothelin family, and they have similar biological activities. This review covers recent advances in the study of the chemical and biological properties of the sarafotoxins and endothelins.

Cloning and sequence analysis of cDNAs encoding precursors of sarafotoxins. Evidence for an unusual "rosary-type" organization.

Sarafotoxins (SRTXs) are 21-amino acid peptides structurally and functionally similar to endothelins (ETs). To understand how SRTXs are overproduced in venom glands of the snakes Atractaspis engaddensis and hence used as toxins, we cloned cDNAs encoding SRTXs and elucidated their nucleotide sequences. We predict that SRTX precursors are large prepropolypeptide chains with an unusual "rosary-type" structure made of 12 successive similar stretches of 40 residues (39 in the first stretch).

How the mongoose can fight the snake: the binding site of the mongoose acetylcholine receptor.

The ligand binding site of the nicotinic acetylcholine receptor (AcChoR) is within a short peptide from the alpha subunit that includes the tandem cysteine residues at positions 192 and 193. To elucidate the molecular basis of the binding properties of the AcChoR, we chose to study nonclassical muscle AcChoRs from animals that are resistant to alpha-neurotoxins. We have previously reported that the resistance of snake AcChoR to alpha-bungarotoxin (alpha-BTX) may be accounted for by several major substitutions in the ligand binding site of the receptor.

The secretion of Duvernoy's gland of Malpolon monspessulanus induces haemorrhage in the lungs of mice.

A toxic protein that induces death of mice with profuse bleeding from the nostrils was isolated from the secretion of Duvernoy's gland of Malpolon monspessulanus (Colubridae). The toxic protein, referred to as CM-b, showed mainly one band on SDS-PAGE corresponding to a mol. wt of 24,000.

Inhibition of the proteolytic activity of hemorrhagin-e from Crotalus atrox venom by antihemorrhagins from homologous serum.

Antihemorrhagic proteins from Crotalus atrox serum were tested for their ability to inhibit the proteolytic activity of the hemorrhagic toxin-e from Crotalus atrox venom and of several other proteolytic enzymes: trypsin, collagenase and thermolysin. The antihemorrhagic proteins inhibited the proteolytic activity of hemorrhagin-e when tested on gelatin type I and collagen type IV, the proteolytic activity of trypsin on photofilm gelatin and the proteolytic activity of whole venom when tested on azocollagen and photofilm gelatin. The antihemorrhagins failed to inhibit the proteolytic activity of trypsin when tested on the specific synthetic substrate N-acetyl-DL-phenylalanine-beta-naphthyl ester (APNE), the activity of microbial collagenase on N-(3-[2-furyl]acryloyl)-Leu-Gly-Pro-Ala (FALGPA) or on azocollagen and the activity of thermolysin on N-(3-[2-furyl]acryloyl)-Gly-Leu amide (FAGLA).

Activity of sarafotoxin/endothelin peptides in the heart and brain of lower vertebrates.

The effects of sarafotoxin-b (SRTX-b) and endothelin-1 (ET-1) were tested in the fish tilapia (Ore niloticus x O. aureus hybrids) and torpedo (Torpedo ocellata), the toad (Bufo viridis), the agama lizard (Agama stellio) and water snake (Natrix tessellata). In isolated heart preparations of the fish and agama, peptide doses of 0.

Endothelin and sarafotoxin: influence on steroid-regulated motility of rat uterus.

The sarafotoxins (SRTX) and endothelins (ET) were shown to influence the motility of the isolated rat uterus by inducing an increase in the rate and in the maximum tension of the spontaneous rhythmic contractions and a suppression of the relaxation phase of these contractions. Ovariectomized rats, 24 weeks post-operation, show no spontaneous motility of their uteri and the SRTX/ET peptides induce only a slight tonic increase in the uterine tension. Treatment with 17 beta estradiol restores spontaneous motility and sensitivity to the SRTX/ET peptides in all three contraction modes.

Endothelins and sarafotoxins: effects on motility, binding properties and phosphoinositide hydrolysis during the estrous cycle of the rat uterus.

The effects of four peptides of the endothelin/sarafotoxin (ET/SRTX) family on the motility of the rat uterus were examined during the different stages of the estrous cycle. ET-1, ET-3, SRTX-b and SRTX-c showed similar effects on the contraction of the uterus: a slight increase in the maximum tension of the spontaneous rhythmic contractions, a suppression of the relaxation phase of these contractions and an increase in their rate. All three effects were concentration dependent.

Contractile effects and binding properties of endothelins/sarafotoxins in the guinea pig ileum.

Seven of the eight known isopeptides of the endothelin/sarafotoxin (ET/SRTX) family were tested on the isolated guinea pig ileum and found to cause a concentration-dependent increase in basal tone. The rate or the amplitude of the spontaneous rhythmic contractions of the ileal smooth muscle were essentially not affected by any of the peptides. The maximum contraction elicited by vasoactive intestinal contractor (VIC) was slightly stronger than that induced by endothelin-1 (ET-1) or sarafotoxin-b (SRTX-b), and significantly stronger than the maximal contractions elicited by sarafotoxin-a (SRTX-a), sarafotoxin-c (SRTX-c), or endothelin-3 (ET-3).

Kinetic and cross-linking studies indicate different receptors for endothelins and sarafotoxins in the ileum and cerebellum.

Kinetics of ligand/receptor interactions using ET-1, ET-3 and SRTX-b were studied and cross-linking experiments carried out in guinea pig ileum and rat cerebellar preparations. Dissociation studies indicate that the two regions are characterized by different receptor subtypes and different modes of ligand binding. Autoradiographic patterns obtained following cross-linking of ET-1 and ET-3 to the different tissues support these conclusions.

Evolution of the sarafotoxin/endothelin superfamily of proteins.

Sixteen protein and nucleic acid sequences from the vasoconstrictor sarafotoxin/endothelin/endothelin-like superfamily of peptides were studied, and the evolutionary relationships between the sarafotoxin and endothelin gene families as well as the phylogenetic topology within each gene family and the three endothelin subfamilies was reconstructed. The endothelin gene family has diverged from an ancestral gene that has experienced an exon duplication event followed by two gene duplication events. The sarafotoxins' lineage diverged from the ancestral gene prior to the first endothelin gene duplication event.

Purification and properties of an antivenom factor from the plasma of the South American rattlesnake (Crotalus durissus terrificus).

The lethal toxicity of Crotalus durissus terrificus (Crotalinae, Viperidae) can be attributed mainly to the presence of a neurotoxic protein, crotoxin, which also shows phospholipase A2 activity. It has been previously demonstrated that both lethal and phospholipase A2 activities of crotoxin can be neutralized by an alpha 1-globulin factor that is present in the homologous blood. Crotalus durissus terrificus plasma also renders some degree of protection to mice against the lethal toxicity of heterologous venoms from snakes of the genus Bothrops (Crotalinae, Viperidae), but not of the genus Micrurus (Elapinae, Elapidae).

The evolutionary history of the sarafotoxin/endothelin/endothelin-like superfamily.

The evolutionary relationships among 17 protein and nucleic acid sequences from the sarafotoxin/endothelin/endothelin-like superfamily of peptides were studied. The endothelin/endothelin-like gene family has diverged from an ancestral gene that has experienced an exon duplication event followed by two complete gene duplications. The sarafotoxin lineage diverged from the ancestral gene prior to the first gene duplication event.