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At least 73 records · Page 4Linked to original sources
PubMed2003

Identification of a novel family of proteins in snake venoms. Purification and structural characterization of nawaprin from Naja nigricollis snake venom.

The three-dimensional structure of nawaprin has been determined by nuclear magnetic resonance spectroscopy. This 51-amino acid residue peptide was isolated from the venom of the spitting cobra, Naja nigricollis, and is the first member of a new family of snake venom proteins referred to as waprins. Nawaprin is relatively flat and disc-like in shape, characterized by a spiral backbone configuration that forms outer and inner circular segments. The two circular segments are held together by four disulfide bonds, three of which are clustered at the base of the molecule. The inner segment contains a short antiparallel beta-sheet, whereas the outer segment is devoid of secondary structures except for a small turn or 310 helix. The structure of nawaprin is very similar to elafin, a human leukocyte elastase-specific inhibitor. Although substantial parts of the nawaprin molecule are well defined, the tips of the outer and inner circular segments, which are hypothesized to be critical for binding interactions, are apparently disordered, similar to that found in elafin. The amino acid residues in these important regions in nawaprin are different from those in elafin, suggesting that nawaprin is not an elastase-specific inhibitor and therefore has a different function in the snake venom.

Amino Acid Sequence↗
PubMed2001

Comparative biochemistry of disintegrins isolated from snake venom: consideration of the taxonomy and geographical distribution of snakes in the genus Echis.

Species in the genus Echis have been classified mainly based on their morphological appearance and the analytical patterns of their serum. However, re-classification of the genus Echis has recently been suggested by taxonomists, toxicologists, and clinicians, since there have been problems with the current classification, such as the efficacy of antivenoms used for treating bites and the broad geographical distribution of Echis snakes. In this study, we purified five novel disintegrins, the platelet aggregation inhibitors pyramidin A and B from the venom of Echis pyramidum, ocellatin from the venom of Echis ocellatus, and leucogastin A and B from the venom of Echis leucogaster, to compare their sequences and allow us to re-evaluate the classification of various species in the genus Echis. Comparison of the amino acid sequences of five new and four known isolated disintegrins from snake venoms of six Echis species and their distribution strongly support the recent re-classification of the genus Echis.

Africa↗
PubMed1998

Molecular evolution of snake toxins: is the functional diversity of snake toxins associated with a mechanism of accelerated evolution?

Recent studies revealed that animal toxins with unrelated biological functions often possess a similar architecture. To tentatively understand the evolutionary mechanisms that may govern this principle of functional prodigality associated with a structural economy, two complementary approaches were considered. One of them consisted of investigating the rates of mutations that occur in cDNAs and/or genes that encode a variety of toxins with the same fold. This approach was largely adopted with phospholipases A2 from Viperidae and to a lesser extent with three-fingered toxins from Elapidae and Hydrophiidae. Another approach consisted of investigating how a given fold can accommodate distinct functional topographies. Thus, a number of topologies by which three-fingered toxins exert distinct functions were investigated either by making chemical modifications and/or mutational analyses or by studying the three-dimensional structure of toxin-target complexes. This review shows that, although the two approaches are different, they commonly indicate that most if not all the surface of a snake toxin fold undergoes natural engineering, which may be associated with an accelerated rate of evolution. The biochemical process by which this phenomenon occurs remains unknown.

Amino Acid Sequence↗
PubMedDate not supplied

Delayed myotoxicity in snake envenoming by the tiger snake group.

Snakebite on the North Coast of New South Wales is not an uncommon cause of envenoming. We report a case of a young woman who presented after a snake bite and did not develop fulminant signs and symptoms of envenoming until 32 h after the bite.

Adult↗
PubMedDate not supplied

[Snake bites by Bothrops moojeni: correlation of the clinical picture with the snake size].

During a period of 19 months (March 1986-September 1987), 22 cases of snake bites caused by Bothrops moojeni in São José do Rio Preto, São Paulo (South-east Brazil) were studied. The animals have their length measured and two groups were constituted: group I - 9 cases with length between 30 and 53 cm and group II - 13 cases with length between 80 and 147 cm. Our results revealed: 1. the local effects--pain and swelling--were frequently mild in group I; 2 - non-clotting blood (bed-side test) occurred in two groups, a little more frequently in group I; 3. local complications--necrosis, compartment syndrome and infection--occurred in more than a half and exclusively in group II, in spite of larger and faster antivenom therapy. We have concluded that larger Bothrops moojeni produced great increment in swelling, necrosis and infection and mild decrement in coagulation action.

Animals↗
PubMed1976

The clotting of a snake (Crotalus viridis Helleri) plasma and its interaction with various snake venoms.

The clotting of C. V. Helleri plasma is not accelerated by the factor X activator or thrombin-like enzymes from its own venom. Clotting of the plasma is accelerated by the factor Xactivator from Russell's viper venom, but not by the thrombin-like enzyme from Agkistrodon Rhodostoma venom ("Arvin"). The prothrombin activator from the Taipan venom clots C.V. Helleri plasma equally well as human plasma, but the thrombin which is produced has a marked specificity for its own fibrinogen, and clots bovine fibrinogen more slowly. C.V. Helleri plasma contains an inhibitor which progressively inactivates bovine factor Xa and thrombin, but the inhibitor is not potentiated by heparin. The slow, protracted clotting of the snake plasma either alone or when mixed with human plasma or bovine fibrinogen suggests that this inhibitor may interfere with the polymerisation of fibrin monomer.

Ancrod↗
PubMed1994

[Snake bite by a poisonous snake. Report of an unusual case].

We report on a 31-year-old white woman, who was bitten in her right calf by a "spitting cobra" (Neia nigricollis) during a safari in Tansania. Minor initial systemic symptoms such as nausea and vomiting were followed by severe oedematous swelling of the extremity after 2-3 h and demarcation of a 2.75 x 2.75 in. area of necrotic skin. The patient returned to her home country, where 8 days after the snake-bite necrosectomy was performed. Antibiotics, anti-inflammatory agents and local therapy with hydrocolloidal wound dressings were administered. With this therapy the lesion healed completely with minor scarring within 5 months. A new Salmonella strain was isolated from the ground of the ulcer.

Adult↗
PubMedDate not supplied

Snake venoms in science and clinical medicine. 3. Neuropharmacological aspects of the activity of snake venoms.

Neuromuscular weakness is a common feature of snake bite. The toxins responsible for weakness either block neuromuscular transmission or they are myotoxic and damage skeletal muscle. In this article the major classes of toxins responsible for causing neuromuscular weakness are described. It is shown how a detailed knowledge of the biochemical and pharmacological properties of the toxins is essential if the clinical problems associated with bites by many species are to be properly understood. It is also shown that such an understanding allows apparent discrepancies between 'laboratory' and 'clinical' findings to be resolved.

Animals↗
PubMed1995

The integrin alpha IIb beta 3 contains distinct and interacting binding sites for snake-venom RGD (Arg-Gly-Asp) proteins. Evidence that the receptor-binding characteristics of snake-venom RGD proteins are related to the amino acid environment flanking the sequence RGD.

We have previously demonstrated [Lu, Williams, Deadman, Salmon, Kakkar, Wilkinson, Baruch, Authi and Rahman (1994) Biochem. J. 304, 929-936] the preferential antagonism of the interactions of the integrin alpha IIb beta 3 on activated platelets with three immobilized glycoprotein ligands (fibrinogen, fibronectin and von Willebrand factor) by a selected panel of snake-venom RGD (Arg-Gly-Asp)-containing proteins including the disintegrins kistrin and elegantin, and the neurotoxin variant dendroaspin. Kistrin and dendroaspin, although structurally unrelated, contain similar amino acids flanking the tripeptide RGD and behaved as identical antagonists preferentially inhibiting platelet adhesion to immobilized fibrinogen as opposed to fibronectin. In contrast, elegantin, which shares extensive sequence similarity with kistrin but has different amino acids around the tripeptide RGD, preferentially inhibited platelet adhesion to immobilized fibronectin as opposed to fibrinogen. To develop further insights into the mechanisms underlying the preferential antagonism shown by the venom proteins in the adhesion studies, we, in the present study, sought to determine the binding properties of kistrin, elegantin and dendroaspin to the alpha IIb beta 3 complex by radioligand kinetic and competition studies. In direct binding experiments, both kistrin and dendroaspin were observed to bind to a single class of binding site on ADP-activated platelets with apparent equilibrium dissociation constant (Kdapp) values of 42 +/- 2 nM and 21 +/- 6 nM respectively. In competition studies, dendroaspin blocked the binding of 125I-labelled kistrin to ADP-activated platelets in a simple competitive manner, with an apparent equilibrium inhibition constant (Kiapp) of 143 +/- 14 nM, from which an indirect Kdapp = 22 nM for dendroaspin was determined. This result suggests that kistrin and dendroaspin bind to the same site on the integrin alpha IIb beta 3 consistent with their similar inhibitory properties. In contrast, elegantin recognized two classes of binding sites on the alpha IIb beta 3 complex with Kdapp values of 10.5 +/- 0.8 nM and 175 +/- 10 nM, and, unlike dendroaspin, did not inhibit the binding of 125I-labelled kistrin to ADP-activated platelets. However, in reciprocal experiments both kistrin and dendroaspin inhibited the binding of 125I-elegantin to ADP-activated platelets in a non-competitive manner, with Kiapp values of 34 +/- 3 nM and 21 +/- 2 nM respectively. Thus elegantin appears to interact with distinct but interacting sites on the alpha IIb beta 3 complex from the binding site of kistrin and dendroaspin, consistent with its distinctive inhibitory preferences as shown in platelet adhesion studies.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Diphosphate↗
PubMed1989

Studies on Australian snake venoms. Part 1: The haemodynamic effects of brown snake (Pseudonaja) species in the dog.

The haemodynamic effects of Brown Snake (Pseudonaja) species (textilis, nuchalis, affinis) were investigated in anaesthetised, mechanically ventilated dogs. Blood pressure decreased to minimal levels five minutes after intravenous envenomation. Hypotension was accompanied by significant decrements in cardiac output and stroke volume and a rise in peripheral vascular resistance. Heart rate increased transiently during 0.5-2.0 minutes after envenomation but had declined below resting levels five minutes after envenomation. No statistically significant change was recorded in central venous pressure. Depression of myocardial contractility is postulated as the mechanism of venom induced hypotension.

Animals↗
PubMed1991

Studies on Australian snake venoms, Part II: The haematological effects of brown snake (Pseudonaja) species in the dog.

The haematological effects of Brown Snake (Pseudonaja) species (textilis, affinis, nuchalis) were studied in anaesthetised, mechanically ventilated dogs. Marked thrombocytopenia, depletion of serum fibrinogen and prolonged prothrombin and activated partial thromboplastin time, were recorded at 5 to 10 and 30 to 40 minutes after intravenous envenomation. Fibrin degradation products were not elevated. Because these haematological effects occurred simultaneously with cardiovascular depression (previously reported), we postulate that hypotension sometimes observed in human envenomation may be due to intravascular coagulation with myocardial ischaemia.

Animals↗
PubMed2005

Snakes across the Strait: trans-Torresian phylogeographic relationships in three genera of Australasian snakes (Serpentes: Elapidae: Acanthophis, Oxyuranus, and Pseudechis).

We analyze the phylogeny of three genera of Australasian elapid snakes (Acanthophis-death adders; Oxyuranus-taipans; Pseudechis-blacksnakes), using parsimony, maximum likelihood, and Bayesian analysis of sequences of the mitochondrial cytochrome b and ND4 genes. In Acanthophis and Pseudechis, we find evidence of multiple trans-Torresian sister-group relationships. Analyses of the timing of cladogenic events suggest crossings of the Torres Strait on several occasions between the late Miocene and the Pleistocene. These results support a hypothesis of repeated land connections between Australia and New Guinea in the late Cenozoic. Additionally, our results reveal undocumented genetic diversity in Acanthophis and Pseudechis, supporting the existence of more species than previously believed, and provide a phylogenetic framework for a reinterpretation of the systematics of these genera. In contrast, our Oxyuranus scutellatus samples from Queensland and two localities in New Guinea share a single haplotype, suggesting very recent (late Pleistocene) genetic exchange between New Guinean and Australian populations.

Animals↗