Genes and evolution of two-domain toxins from lynx spider venom

AbstractSpiderines are comparatively long polypeptide toxins (∼110 residues) from lynx spiders (genus Oxyopes). They are built of an N-terminal linear cationic domain (∼40 residues) and a C-terminal knottin domain (∼60 residues). The linear domain empowers spiderines with strong cytolytic activity. In the present work we report 16 novel spiderine sequences from Oxyopes takobius and Oxyopes lineatus classified into two subfamilies. Strikingly, negative selection acts on both linear and knottin domains. Genes encoding Oxyopes two-domain toxins were sequenced and found to be intronless. We further discuss a possible scenario of lynx spider modular toxin evolution

Spider Venom Peptides for Gene Therapy of Chlamydia Infection ▿

Spider venoms are vast natural pharmacopoeias selected by evolution. The venom of the ant spider Lachesana tarabaevi contains a wide variety of antimicrobial peptides. We tested six of them (latarcins 1, 2a, 3a, 4b, 5, and cytoinsectotoxin 1a) for their ability to suppress Chlamydia trachomatis infection. HEK293 cells were transfected with plasmid vectors harboring the genes of the selected peptides. Controlled expression of the transgenes led to a significant decrease of C. trachomatis viability inside the infected cells

Refined structure of BeM9 reveals arginine hand, an overlooked structural motif in scorpion toxins affecting sodium channels

Sodium channel alpha-toxins from scorpion venom (α-NaTx) inhibit the inactivation of voltage-gated sodium channels. We used solution NMR to investigate the structure of BeM9 toxin from Mesobuthus eupeus scorpion, a prototype α-NaTx classified as an "α-like" toxin due to its wide spectrum of activity on insect and mammalian channels. We identified a new motif that we named "arginine hand," whereby arginine side chain forms several hydrogen bonds with main chain atoms. The arginine hand was found in the "specificity module," a part of the molecule that dictates toxin selectivity; and just single arginine-to-lysine point mutation drastically changed BeM9 selectivity profile.status: publishe

Lachesana tarabaevi, an expert in membrane-active toxins

In the present study, we show that venom of the ant spider Lachesana tarabaevi is unique in terms of molecular composition and toxicity. Whereas venom of most spiders studied is rich in disulfide-containing neurotoxic peptides, L. tarabaevi relies on the production of linear (no disulfide bridges) cytolytic polypeptides. We performed full-scale peptidomic examination of L. tarabaevi venom supported by cDNA library analysis. As a result, we identified several dozen components, and a majority (∼80% of total venom protein) exhibited membrane-active properties. In total, 33 membrane-interacting polypeptides (length of 18-79 amino acid residues) comprise five major groups: repetitive polypeptide elements (Rpe), latarcins (Ltc), met-lysines (MLys), cyto-insectotoxins (CIT) and latartoxins (LtTx). Rpe are short (18 residues) amphiphilic molecules that are encoded by the same genes as antimicrobial peptides Ltc 4a and 4b. Isolation of Rpe confirms the validity of the iPQM (inverted processing quadruplet motif) proposed to mark the cleavage sites in spider toxin precursors that are processed into several mature chains. MLys (51 residues) present 'idealized' amphiphilicity when modelled in a helical wheel projection with sharply demarcated sectors of hydrophobic, cationic and anionic residues. Four families of CIT (61-79 residues) are the primary weapon of the spider, accounting for its venom toxicity. Toxins from the CIT 1 and 2 families have a modular structure consisting of two shorter Ltc-like peptides. We demonstrate that in CIT 1a, these two parts act in synergy when they are covalently linked. This finding supports the assumption that CIT have evolved through the joining of two shorter membrane-active peptides into one larger molecule

Apamin structure and pharmacology revisited

Apamin is often cited as one of the few substances selectively acting on small-conductance Ca2+-activated potassium channels (KCa2). However, published pharmacological and structural data remain controversial. Here, we investigated the molecular pharmacology of apamin by two-electrode voltage-clamp in Xenopus laevis oocytes and patch-clamp in HEK293, COS7, and CHO cells expressing the studied ion channels, as well as in isolated rat brain neurons. The microtitre broth dilution method was used for antimicrobial activity screening. The spatial structure of apamin in aqueous solution was determined by NMR spectroscopy. We tested apamin against 42 ion channels (KCa, KV, NaV, nAChR, ASIC, and others) and confirmed its unique selectivity to KCa2 channels. No antimicrobial activity was detected for apamin against Gram-positive or Gram-negative bacteria. The NMR solution structure of apamin was deposited in the Protein Data Bank. The results presented here demonstrate that apamin is a selective nanomolar or even subnanomolar-affinity KCa2 inhibitor with no significant effects on other molecular targets. The spatial structure as well as ample functional data provided here support the use of apamin as a KCa2-selective pharmacological tool and as a template for drug design