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To search for compounds with antiprotozoal activity, effects of snake venoms on the ciliates Tetrahymena pyriformis was studied. T. pyriformis from subkingdom of Protozoa, including the protozoal pathogens, was used as a model organism to select the venoms that are the most active against parasitic protozoans. Various concentrations of venoms were added to the cells, and the cells that survived after 24 h were counted. Among the six snake species from the Viperidae family, the venom of the viper Vipera berus, which completely killed the cells at 49 μg/mL, was the most active. Among four species from the Elapidae family, the previously studied cobra venoms containing cytotoxins with strong antiprotozoal activity as well as the venom of krait Bungarus multicinctus (10 μg/mL) were the most active. The venoms of the pit vipers and Nikolsky's viper did not show any activity at 12.5 mg/mL. Thus, the venoms of V. berus and B. multicinctus are promising for the isolation of new antiprotozoal compounds., (© 2022. Pleiades Publishing, Ltd.)

The venoms of snakes from Viperidae family mainly influence the function of various blood components. However, the published data indicate that these venoms contain also neuroactive components, the most studied being neurotoxic phospholipases A₂ (PLA₂s). Earlier we have shown (Gorbacheva et al., 2008) that several Viperidae venoms blocked nicotinic acetylcholine receptors (nAChRs) and voltage-gated Ca²+ channels in isolated identified neurons of the fresh-water snail Lymnaea stagnalis. In this paper, we report on isolation from puff adder Bitis arietans venom and characterization of a novel protein bitanarin that reversibly blocks nAChRs. To isolate the protein, the venom of B. arietans was fractionated by gel-filtration, ion-exchange and reversed phase chromatography and fractions obtained were screened for capability to block nAChRs. The isolated protein competed with [¹²⁵I]iodinated α-bungarotoxin for binding to human α7 and Torpedo californica nAChRs, as well as to acetylcholine-binding protein from L. stagnalis, the IC₅₀ being 20 ± 1.5, 4.3 ± 0.2, and 10.6 ± 0.6 μM, respectively. It also blocked reversibly acetylcholine-elicited current in isolated L. stagnalis neurons with IC₅₀ of 11.4 μM. Mass-spectrometry analysis determined the molecular mass of 27.4 kDa and the presence of 28 cysteine residues forming 14 disulphide bonds. Edman degradation of the protein and tryptic fragments showed its similarity to PLA₂s from snake venoms. Indeed, the protein possessed high PLA₂ activity, which was 1.95 mmol/min/μmol. Bitanarin is the first described PLA₂ that contains 14 disulphide bonds and the first nAChR blocker possessing PLA₂ activity., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Cysteine-rich proteins found in animal venoms (CRISP-Vs) are members of a large family of cysteine-rich secretory proteins (CRISPs). CRISP-Vs acting on different ion channels were found in venoms or mRNA (cDNA) encoding CRISP-Vs were cloned from snakes of three main families (Elapidae, Colubridae and Viperidae). About thirty snake CRISP-Vs were sequenced so far, however no complete sequence for CRISP-V from Viperinae subfamily was reported. We have cloned and sequenced for the first time cDNAs encoding CRISP-Vs from Vipera nikolskii and Vipera berus vipers (Viperinae). The deduced mature CRISP-V amino acid sequences consist of 220 amino acid residues. Phylogenetic analysis showed that viper proteins are closely related to those of Crotalinae snakes. The presence of CRISP-V in the V. berus venom was revealed using a combination of gel-filtration chromatography, electrophoresis and MALDI mass spectrometry. The finding of the putative channel blocker in viper venom may indicate its action on prey nervous system.

The existing data indicate that snake venom is most toxic towards the natural vertebrate preys. Several species of snake include arthropods in their food. However, there is no available data on the toxicity of venom from entomophagous snakes towards their prey. We have studied the toxicity of venom from vipers of Pelias group towards crickets Gryllus assimilis. The Pelias group includes several closely related viper species inhabiting mainly the South European part of Russia, and they differ in their feeding preferences. Snakes from the Vipera renardi, Vipera lotievi, Vipera kaznakovi, and Vipera orlovi species feed on wide range of animals including insects, whereas snakes from Vipera berus and Vipera nikolskii species do not include insects in their diet. We have found that the venom from vipers that include insects in their diet possesses greater toxicity towards crickets. The greatest toxicity was observed for the venom from V. lotievi, which displays a preference for insects in its diet. Therefore, based on our data, we suggest that the viper entomophagy is not a result of behavior plasticity, but is probably determined at a genetic level.