Nucleotide sequence and structure analysis of cDNAs encoding short-chain neurotoxins from venom glands of a sea snake (Aipysurus laevis)

Toxin Fused with SUMO Tag: A New Expression Vector Strategy to Obtain Recombinant Venom Toxins with Easy Tag Removal inside the Bacteria

Many animal toxins may target the same molecules that need to be controlled in certain pathologies; therefore, some toxins have led to the formulation of drugs that are presently used, and many other drugs are still under development. Nevertheless, collecting sufficient toxins from the original source might be a limiting factor in studying their biological activities. Thus, molecular biology techniques have been applied in order to obtain large amounts of recombinant toxins into Escherichia coli. However, most animal toxins are difficult to express in this system, which results in insoluble, misfolded, or unstable proteins. To solve these issues, toxins have been fused with tags that may improve protein expression, solubility, and stability. Among these tags, the SUMO (small ubiquitin-related modifier) has been shown to be very efficient and can be removed by the Ulp1 protease. However, removing SUMO is a labor- and time-consuming process. To enhance this system, here we show the construction of a bicistronic vector that allows the expression of any protein fused to both the SUMO and Ulp1 protease. In this way, after expression, Ulp1 is able to cleave SUMO and leave the protein interest-free and ready for purification. This strategy was validated through the expression of a new phospholipase D from the spider Loxosceles gaucho and a disintegrin from the Bothrops insularis snake. Both recombinant toxins showed good yield and preserved biological activities, indicating that the bicistronic vector may be a viable method to produce proteins that are difficult to express.

Marine Natural Products from New Caledonia--A Review

Marine micro- and macroorganisms are well known to produce metabolites with high biotechnological potential. Nearly 40 years of systematic prospecting all around the New Caledonia archipelago and several successive research programs have uncovered new chemical leads from benthic and planktonic organisms. After species identification, biological and/or pharmaceutical analyses are performed on marine organisms to assess their bioactivities. A total of 3582 genera, 1107 families and 9372 species have been surveyed and more than 350 novel molecular structures have been identified. Along with their bioactivities that hold promise for therapeutic applications, most of these molecules are also potentially useful for cosmetics and food biotechnology. This review highlights the tremendous marine diversity in New Caledonia, and offers an outline of the vast possibilities for natural products, especially in the interest of pursuing collaborative fundamental research programs and developing local biotechnology programs.

Danger in the reef: Proteome, toxicity, and neutralization of the venom of the olive sea snake, Aipysurus laevis

Four specimens of the olive sea snake, Aipysurus laevis, were collected off the coast of Western Australia, and the venom proteome was characterized and quantitatively estimated by RP-HPLC, SDS-PAGE, and MALDI-TOF-TOF analyses. A. laevis venom is remarkably simple and consists of phospholipases A2 (71.2%), three-finger toxins (3FTx; 25.3%), cysteine-rich secretory proteins (CRISP; 2.5%), and traces of a complement control module protein (CCM; 0.2%). Using a Toxicity Score, the most lethal components were determined to be short neurotoxins. Whole venom had an intravenous LD50 of 0.07 mg/kg in mice and showed a high phospholipase A2 activity, but no proteinase activity in vitro. Preclinical assessment of neutralization and ELISA immunoprofiling showed that BioCSL Sea Snake Antivenom was effective in cross-neutralizing A. laevis venom with an ED50 of 821 μg venom per mL antivenom, with a binding preference towards short neurotoxins, due to the high degree of conservation between short neurotoxins from A. laevis and Enhydrina schistosa venom. Our results point towards the possibility of developing recombinant antibodies or synthetic inhibitors against A. laevis venom due to its simplicity.

Snake postsynaptic neurotoxins: gene structure, phylogeny and applications in research and therapy

Snake venoms are complex mixtures of biologically active polypeptides that target a variety of vital physiological functions in mammals. alpha-Neurotoxins, toxins that cause paralysis by binding to the nicotinic receptors at the postsynaptic region of the neuromuscular junction have been widely studied in terms of their structure-function relationships as well as gene structure, organization and expression. In this review, we describe the structure of alpha-neurotoxin genes and discuss their evolutionary relationships. Almost all members of neurotoxins have been found to exhibit a common evolutionary origin. The importance of alpha-neurotoxins in therapy and research has also been discussed to highlight their potential applications especially in the area of drug discovery.

Postsynaptic α-Neurotoxin Gene of the Spitting Cobra, Naja naja sputatrix: Structure, Organization, and Phylogenetic Analysis

The venom of the spitting cobra, Naja naja sputatrixcontains highly potent α-neurotoxins (NTXs) in addition to phospholipase A2 (PLA2) and cardiotoxin (CTX). In this study, we report the complete characterization of three genes that are responsible for the synthesis of three isoforms of α-NTX in the venom of a single spitting cobra. DNA amplification by long-distance polymerase chain reaction (LD-PCR) and genome walking have provided information on the gene structure including their promoter and 5′ and 3′ UTRs. Each NTX isoform is ∼4 kb in size and contains three exons and two introns. The sequence homology among these isoforms was found to be 99%. Two possible transcription sites were identified by primer extension analysis and they corresponded to the adenine (A) nucleotide at positions +1 and −45. The promoter also contains two TATA boxes and a CCAAT box. Putative binding sites for transcriptional factors AP-2 and GATA are also present. The high percentage of similarity observed among the NTX gene isoforms of N. n. sputatrix as well as with the α-NTX and κ-NTX genes from other land snakes suggests that the NTX gene has probably evolved from a common ancestral gene.

[The genomic DNA sequences reported in this paper have been submitted to GenBank databases under accession nos. AF096999 to AF097001.]

Four new postsynaptic neurotoxins from Naja naja sputatrix venom: cDNA cloning, protein expression, and phylogenetic analysis

cDNAs encoding 4 short chain alpha-neurotoxins from Malayan spitting cobra (Naja naja sputatrix) venom were cloned and expressed in Escherichia coli. The recombinant toxins possessed identical amino acid sequences to alpha-neurotoxins. This is the first report on cloning and expression of isoforms of neurotoxins from a species of spitting cobra. Two of these isoforms were also identified in the crude venom by reverse phase-high performance liquid chromatography (RP-HPLC), capillary electrophoresis followed by mass spectrometry and characterized by protein sequencing. Based on the variable amino acid residues, the neurotoxins in N. n. sputatrix could be assigned to 2 major groups, 10E11T and 10Q11A, which could be further subdivided into 10E11T28S: 10E11T28G and 10Q11A28S; 10Q11A28G respectively. These substitutions were also found to be unique to N. n. sputatrix neurotoxins. Phylogenetic analysis based on molecular properties of the toxins provided further support for the classification of N. n. sputatrix neurotoxin into 2 fundamental groups.

Black widow spider toxins: the present and the future

The venom of the black widow spider Latrodectus mactans tredisimguttatus was found to contain a family of high molecular weight toxic proteins inducing a sharp increase in transmitter secretion from the affected nerve endings, which are highly specific for vertebrates, or for insects, or for crustaceans. Along with the known alpha-latrotoxin, five latroinsectotoxins affecting the neurotransmitter release from presynaptic endings of insects and one latrocrustatoxin active only for crustaceans were isolated and studied in detail. Alpha-latrotoxin provokes a massive transmitter release from different nerve endings of vertebrates, whereas other toxins increase the secretion process either in insects or crustaceans. The cDNAs encoding the putative alpha-latrotoxin and two latroinsectotoxins (alpha-latroinsectotoxin and delta-latroinsectotoxin) precursors were cloned and sequenced. These toxins are polypeptides of about 1000 amino acids and share a high level of amino acid identity. Analysis of amino acid sequences of the three toxins reveals the central regions being almost entirely composed of series of ankyrin-like repeats. Taking into account the size and multifunctional properties of latrotoxin its molecule can be divided into several functional domains. Immunochemical experiments indicated the presence in the alpha-latrotoxin molecule of distinguishable functional domains responsible for ionophoric and secretogenic actions. The highly purified preparation of alpha-latrotoxin was shown to contain an additional component, a low molecular weight protein structurally related to crustacean hyperglycemic hormones. Several attempts were made to characterize and isolate alpha-latrotoxin receptor components. The existence of Ca-dependent and Ca-independent binding proteins was found in the presynaptic membrane preparations.

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.

The nephrotoxicity of fractionated components of Aipysurus laevis venom

Six major venom fractions were obtained when crude Aipysurus laevis (Olive sea snake) venom was fractionated by standard HPLC techniques. Subcutaneous doses of between 9.5-20.3 micrograms venom/kg body weight were injected into male Quackenbush mice, showing that all six fractions of A. laevis venom are nephrotoxic, producing renal lesions within 24 hrs and lasting for up to three months. It is postulated that each fraction contains a nephrotoxic component, suggesting a core or common biochemical structure, the nature of which is to yet to be determined; and those from different fractions may act synergistically. The resulting renal lesions are no different from those seen in our previous whole venom study, but the severity is less and shorter in duration. A significant difference is that after fraction injection, the kidneys returned to normality after two months, with minor segmental glomerulosclerosis being the only remaining stigma of the previous damage. This is contrary to the whole venom-induced tubulo-interstitial nephritis with cystic changes seen after three months of envenomation. All fractions also increase the granularity of the juxtaglomerular cells, for reasons unknown.

Isolation and identification of angiotensin-like peptides from the plasma of the snake Bothrops jararaca

Two distinct hypertensive peptides were purified and characterized from Bothrops jararaca (Bj) plasma incubated at pH 4, 37 degrees C, 24 hr. These peptides were active on rat and Bj blood pressure, on rat isolated uterus, on guinea pig isolated ileum and on Bj isolated duodenum. At the releasing conditions no further activities were found for kininases, angiotensinases or angiotensin converting enzymes. The peptides were purified by ethanol/ether extraction, Sephadex G-25 gel filtration, semipreparative reverse-phase (C-18) HPLC and analytical (C-18) HPLC. The amino-acid sequences of the purified peptides corresponded to (Ile5)AII and (Val5-Tyr9)AI and their molecular masses were confirmed by mass spectrometry as 1046.6 and 1348.0 respectively. The presence of those two angiotensins on Bj plasma may have some evolutionary significance since (Ile5)AII is known as a mammalian angiotensin and (Val5)AII as a non-mammalian one.

Structure of the low molecular weight protein copurified with alpha-latrotoxin

Some samples of latrotoxin purified from the black widow spider venom contain two components: alpha-latrotoxin (M(r) approximately 130,000) and a low mol. wt protein with M(r) about 8000. Clones carrying the cDNA sequence for the low mol. wt protein copurified with alpha-latrotoxin were isolated from spider venom glands. Nucleotide sequence analysis of the cloned cDNA revealed the primary structure of the polypeptide to be 18 amino acids signal peptide and 70 amino acids protein chain with mol. wt of 7947 and pI of approximately 4.0. The protein exhibits certain structural homology with erabutoxin-a from the sea snake.

Amino acid sequence of a muscarinic toxin deduced from the cDNA nucleotide sequence

We prepared a cDNA library from venom glands of the green mamba Dendroaspis angusticeps. A cDNA clone was isolated using an appropriate nucleotide probe. The nucleotide sequence codes for a 21 residue signal peptide followed by a 65 residue protein having the amino acid sequence of muscarinic toxin 2, as confirmed in the accompanying paper (Karlsson, E., Risinger, C., Jolkkonen, M., Wernstedt, C. and Adem, A.). The cDNA encoding the muscarinic toxin has been compared with those encoding other snake toxins. There are close similarities with short-chain curaremimetic neurotoxins.