The presence of cytotoxic CD4 and exhausted-like CD8+ T-cells is a signature of active tuberculosis.

Chronic infections induce CD4+ T-cells with cytotoxic functions (CD4 CTLs); at present, it is still unknown whether latent tuberculosis (LTB) and active tuberculosis (ATB) induce CD4 CTLs. Plasma and cells from four patient groups-uninfected contact (UC), LTB, and ATB (divided as sensitive [DS-TB]- or resistant [DR-TB]-drug)-were evaluated by flow cytometry, q-PCR, and proteomics. The data showed that ATB patients had an increased frequency of CD4+ T-cells and a decreased frequency of CD8+ T-cells. The latter displays an exhausted-like profile characterized by CD39, CD279, and TIM-3 expression. ATB had a high frequency of CD4 + perforin+ cells, suggesting a CD4 CTL profile. The expression (at the transcriptional level) of granzyme A, granzyme B, granulysin, and perforin, as well as the genes T-bet (Tbx21) and NKG2D (Klrk1), in enriched CD4+ T-cells, confirmed the cytotoxic signature of CD4+ T-cells during ATB (which was stronger in DS-TB than in DR-TB). Moreover, proteomic analysis revealed the presence of HSP70 (in DS-TB) and annexin A5 (in DR-TB), which are molecules that have been associated with favoring the CD4 CTL profile. Finally, we found that lipids from Mycobacterium tuberculosis increased the presence of CD4 CTLs in DR-TB patients. Our data suggest that ATB is characterized by exhausted-like CD8+ T-cells, which, together with a specific microenvironment, favor the presence of CD4 CTLs.

Structure, function, and chemical synthesis of Vaejovis mexicanus peptide 24: a novel potent blocker of Kv1.3 potassium channels of human T lymphocytes.

Animal venoms are rich sources of ligands for studying ion channels and other pharmacological targets. Proteomic analyses of the soluble venom from the Mexican scorpion Vaejovis mexicanus smithi showed that it contains more than 200 different components. Among them, a 36-residue peptide with a molecular mass of 3864 Da (named Vm24) was shown to be a potent blocker of Kv1.3 of human lymphocytes (K(d) ∼ 3 pM). The three-dimensional solution structure of Vm24 was determined by nuclear magnetic resonance, showing the peptide folds into a distorted cystine-stabilized α/ß motif consisting of a single-turn α-helix and a three-stranded antiparallel ß-sheet, stabilized by four disulfide bridges. The disulfide pairs are formed between Cys6 and Cys26, Cys12 and Cys31, Cys16 and Cys33, and Cys21 and Cys36. Sequence analyses identified Vm24 as the first example of a new subfamily of α-type K(+) channel blockers (systematic number α-KTx 23.1). Comparison with other Kv1.3 blockers isolated from scorpions suggests a number of structural features that could explain the remarkable affinity and specificity of Vm24 toward Kv1.3 channels of lymphocytes.

Quantitative proteomic analysis reveals high interference on protein expression of H9c2 cells activated with glucose and cardiotonic steroids.

In recent decades, the incidence of death and morbidity due to diabetes has increased worldwide, causing a high social and economic impact. Diabetes is a major cause of blindness, kidney failure, heart attack, stroke and lower limb amputation. However, the molecular mechanisms that make the heart and kidneys the main targets of diabetes are not completely understood. To better understand the complex biochemical mechanism of diabetic cardiomyopathy, we investigated the effects of hyperglycemia with concomitant digoxin and ouabain stimulation in H9c2 cells. Total extracted proteins were analyzed by label-free LC-MS/MS, quantified by Scaffold software and validated by parallel reaction monitoring (PRM) methodology. Here, we show that the eukaryotic initiation factors (Eifs) and elongation factors (Eefs) Eif3f, Eef2 and Eif4a1 are overexpressed following cardiotonic steroid (CTS) stimulation. Similarly, the expression of four 14-3-3 proteins that play a key role in cardiac ventricular compaction was altered after CTS stimulation. In total, the expression of nine protein groups was altered in response to the stimulation of H9c2 cells. Here, the biological consequences of these changes are discussed in depth. SIGNIFICANCE: Hyperglycemia is the main physiological condition that provokes tissue and vascular injuries in heart of diabetic patients. However, the changings at large scale in the expression of proteins of cardiomyocytes generated by this condition was not yet studied. Here we report for the first time the altered biosynthesis of nine groups of proteins of H9c2 cells activated by high glucose concentrations and by cardiotonic steroids (CTS). Furthermore, the increased biosynthesis of Eifs, Eefs and 14-3-3 protein groups by CTS, which play a crucial role in cardiomyopathies are original data reported in this work. These findings not only enhance our knowledge concerning to the effects of hyperglycemia and CTS on H9c2 cells but also indicate potential molecular targets to interfere in diabetes cardiomyopathy progression.

Structural characterization of five post-translationally modified isomorphs of a novel putative delta-conotoxin from the vermivorous snail Conus delessertii from the Mexican Caribbean Sea.

A novel peptide, de7b, was isolated from the venom of Conus delessertii, a worm-hunting species collected in the Caribbean Sea off the Yucatan Peninsula. Its primary structure was determined by automated Edman degradation and confirmed by mass spectrometry: it contains 28 amino acids, including six Cys residues. Peptide de7b is the second, O-conotoxin-like peptide isolated from the venom of this species, and it exists in different post-translationally modified isomorphs, some of which contain gamma-carboxy-glutamate (gamma) and/or 4-hydroxy-proline (O) at positions 4, 7, and/or 14. Its primary structure is DCI(P/O)GG(E/gamma)NCDVFR(O/P)YRCCSGYCILLLCA, with molecular masses varying from 3078.6 to 3154.6Da, depending on the number and kind of modified amino acid residues. Peptide de7b shows significant sequence identity with several O-conotoxins purified and biologically characterized from molluscivorous and piscivorous cone snails of the Indo-Pacific region, the tropical Atlantic and Eastern Pacific Oceans, especially with the delta-conotoxins but also with the omega-conotoxins from molluscivorous species, which suggests that it might affect voltage-gated Na(+) or Ca(2+)channels. Peptide de7b has 32% sequence identity with putative gamma-conotoxin de7a, previously characterized from the same species; both peptides contain the same number of amino acid residues and of non-Cys residues between the pairs of consecutive Cys residues. However, these peptides have charge differences at seven positions within the N-terminal half indicating that they might have distinct molecular targets that remain to be identified.

Dissecting Toxicity: The Venom Gland Transcriptome and the Venom Proteome of the Highly Venomous Scorpion Centruroides limpidus (Karsch, 1879).

Venom glands and soluble venom from the Mexican scorpion Centruroides limpidus (Karsch, 1879) were used for transcriptomic and proteomic analyses, respectively. An RNA-seq was performed by high-throughput sequencing with the Illumina platform. Approximately 80 million reads were obtained and assembled into 198,662 putative transcripts, of which 11,058 were annotated by similarity to sequences from available databases. A total of 192 venom-related sequences were identified, including Na+ and K+ channel-acting toxins, enzymes, host defense peptides, and other venom components. The most diverse transcripts were those potentially coding for ion channel-acting toxins, mainly those active on Na+ channels (NaScTx). Sequences corresponding to ß- scorpion toxins active of K+ channels (KScTx) and λ-KScTx are here reported for the first time for a scorpion of the genus Centruroides. Mass fingerprint corroborated that NaScTx are the most abundant components in this venom. Liquid chromatography coupled to mass spectometry (LC-MS/MS) allowed the identification of 46 peptides matching sequences encoded in the transcriptome, confirming their expression in the venom. This study corroborates that, in the venom of toxic buthid scorpions, the more abundant and diverse components are ion channel-acting toxins, mainly NaScTx, while they lack the HDP diversity previously demonstrated for the non-buthid scorpions. The highly abundant and diverse antareases explain the pancreatitis observed after envenomation by this species.

αD-Conotoxins in Species of the Eastern Pacific: The Case of Conus princeps from Mexico.

Conus snails produce venoms containing numerous peptides such as the α-conotoxins (α-CTXs), which are well-known nicotinic acetylcholine receptor (nAChR) antagonists. Thirty-eight chromatographic fractions from Conus princeps venom extract were isolated by RP-HPLC. The biological activities of 37 fractions (0.07 µg/µL) were assayed by two-electrode voltage clamp on human α7 nAChRs expressed in Xenopus laevis oocytes. Fractions F7 and F16 notably inhibited the response elicited by acetylcholine by 52.7 ± 15.2% and 59.6 ± 2.5%, respectively. Fraction F7 was purified, and an active peptide (F7-3) was isolated. Using a combination of Edman degradation, mass spectrometry, and RNASeq, we determined the sequence of peptide F7-3: AVKKTCIRSTOGSNWGRCCLTKMCHTLCCARSDCTCVYRSGKGHGCSCTS, with one hydroxyproline (O) and a free C-terminus. The average mass of this peptide, 10,735.54 Da, indicates that it is a homodimer of identical subunits, with 10 disulfide bonds in total. This peptide is clearly similar to αD-CTXs from species of the Indo-Pacific. Therefore, we called it αD-PiXXA. This toxin slowly and reversibly inhibited the ACh-induced response of the hα7 nAChR subtype, with an IC50 of 6.2 µM, and it does not affect the hα3ß2 subtype at 6.5 µM.

Proteomic analysis of the venom from the fish eating coral snake Micrurus surinamensis: novel toxins, their function and phylogeny.

The protein composition of the soluble venom from the South American fish-eating coral snake Micrurus surinamensis surinamensis, here abbreviated M. surinamensis, was separated by RP-HPLC and 2-DE, and their components were analyzed by automatic Edman degradation, MALDI-TOF and ESI-MS/MS. Approximately 100 different molecules were identified. Sixty-two components possess molecular masses between 6 and 8 kDa, are basically charged molecules, among which are cytotoxins and neurotoxins lethal to fish (Brachidanios rerio). Six new toxins (abbreviated Ms1-Ms5 and Ms11) were fully sequenced. Amino acid sequences similar to the enzymes phospholipase A2 and amino acid oxidase were identified. Over 20 additional peptides were identified by sequencing minor components of the HPLC separation and from 2-DE gels. A functional assessment of the physiological activity of the six toxins was also performed by patch clamp using muscular nicotinic acetylcholine receptor assays. Variable degrees of blockade were observed, most of them reversible. The structural and functional data obtained were used for phylogenetic analysis, providing information on some evolutionary aspects of the venom components of this snake. This contribution increases by a factor of two the total number of alpha-neurotoxins sequenced from the Micrurus genus in currently available literature.

New insights into the proteomic characterization of the coral snake Micrurus pyrrhocryptus venom.

A proteomic analysis of the soluble venom of the coral snake Micrurus pyrrhocryptus is reported in this work. The whole soluble venom was separated by RP-HPLC and the molecular weights of its components (over 100) were determined by mass spectrometry. Three main sets of components were identified, corresponding to peptides with molecular masses from 5 to 8 kDa, proteins from 12 to 16 kDa and proteins from 20 to 30 kDa. Two components were fully sequenced: one α-neurotoxic peptide of 7210 Da with slight blocking activity of the nicotinic acetylcholine receptor (nAChR) and a phospholipase A2 (PLA2) with molecular weight 13517 Da and no effect on the nAChR. PLA2 activity was evaluated for all RP-HPLC components. In addition, N-terminal sequence was obtained for eleven components using Edman degradation. Among these, three were similar to known PLA2's, six to three-finger toxins (3FTx) and one to Kunitz-type serine protease inhibitors. Two-dimensional gel electrophoresis of the venom allowed the separation of about thirty spots with components of molecular weights from 25 to 70 kDa. Seventeen spots were recovered from the gel, digested with trypsin and the corresponding peptides (85) were sequenced by MS/MS allowing identification of amino acid sequences with similarities to snake venom metalloproteases (SVMP), PLA2's, L-amino acid oxidases (LAAO), acetylcholinesterases (AChE) and serine proteases (SP). In addition, LC-MS analysis of peptides obtained from tryptic digestion of whole soluble venom allowed the identification of 695 peptides, whose amino acid sequence could correspond to at least 355 components found in other snake venoms, where C-type lectins, vespryns, zinc finger proteins, and waprins were found, among others. These results show the complexity of the venom and provide important knowledge for future work on identification and activity determination of venom components from this coral snake.

The diversity of venom components of the scorpion species Paravaejovis schwenkmeyeri (Scorpiones: Vaejovidae) revealed by transcriptome and proteome analyses.

The recent publication of high-throughput transcriptomic and proteomic analyses of scorpion venom glands has increased our knowledge on the biodiversity of venom components. In this contribution, we report the transcriptome of the venom gland and the proteome of the venom for the scorpion species Paravaejovis schwenkmeyeri, a member of the family Vaejovidae. We report 138 annotated transcripts encoding putative peptides/proteins with sequence identity to known venom components available from different databases. A fingerprint analysis containing the molecular masses of 212 components of the whole soluble venom revealed molecular weights of approximately 700 to 13,800 Da, with most detected proteins ranging from 1500 to 3000 Da. Amino acid sequencing of venom components by LC-MS/MS allowed the identification of fragments from 27 peptides encoded by transcripts found in the transcriptome analysis. Enzymatic assays conducted with the soluble venom fraction confirmed the presence of enzymes such as hyaluronidases and phospholipases. The database presented here increases our general knowledge on the biodiversity of venom components from neglected non-buthid scorpions.

Proteomic analysis of the venom and characterization of toxins specific for Na+ - and K+ -channels from the Colombian scorpion Tityus pachyurus.

The Colombian scorpion Tityus pachyurus is toxic to humans and is capable of producing fatal accidents, but nothing is known about its venom components. This communication reports the separation of at least 57 fractions from the venom by high performance liquid chromatography. From these, at least 104 distinct molecular weight compounds were identified by mass spectrometry analysis. The complete amino acid sequences of three peptides were determined and the partial sequences of three others were also identified. Electrophysiological experiments conducted with ion-channels expressed heterologously on Sf9 cells showed the presence of a potent Shaker B K(+)-channel blocker. This peptide (trivial name Tpa1) contains 23 amino acid residues closely packed by three disulfide bridges with a molecular mass of 2,457 atomic mass units. It is the third member of the sub-family 13, for which the systematic name is proposed to be alpha-KTx13.3. The mice assay showed clearly the presence of toxic peptides to mammals. One of them named Tpa2, containing 65 amino acid residues with molecular mass of 7,522.5 atomic mass units, is stabilized by four disulfide bridges. It was shown to modify the Na(+)-currents of F-11 and TE671 cells in culture, similar to the beta scorpion toxins. These results demonstrate the presence of toxic peptides in the venom of T. pachyurus and confirm that accidents with this species of scorpion should be considered an important human hazard in Colombia.

Novel alpha-conotoxins from Conus spurius and the alpha-conotoxin EI share high-affinity potentiation and low-affinity inhibition of nicotinic acetylcholine receptors.

alpha-Conotoxins from marine snails are known to be selective and potent competitive antagonists of nicotinic acetylcholine receptors. Here we describe the purification, structural features and activity of two novel toxins, SrIA and SrIB, isolated from Conus spurius collected in the Yucatan Channel, Mexico. As determined by direct amino acid and cDNA nucleotide sequencing, the toxins are peptides containing 18 amino acid residues with the typical 4/7-type framework but with completely novel sequences. Therefore, their actions (and that of a synthetic analog, [gamma15E]SrIB) were compared to those exerted by the alpha4/7-conotoxin EI from Conus ermineus, used as a control. Their target specificity was evaluated by the patch-clamp technique in mammalian cells expressing alpha(1)beta(1)gammadelta, alpha(4)beta(2) and alpha(3)beta(4) nicotinic acetylcholine receptors. At high concentrations (10 microm), the peptides SrIA, SrIB and [gamma15E]SrIB showed weak blocking effects only on alpha(4)beta(2) and alpha(1)beta(1)gammadelta subtypes, but EI also strongly blocked alpha(3)beta(4) receptors. In contrast to this blocking effect, the new peptides and EI showed a remarkable potentiation of alpha(1)beta(1)gammadelta and alpha(4)beta(2) nicotinic acetylcholine receptors if briefly (2-15 s) applied at concentrations several orders of magnitude lower (EC(50), 1.78 and 0.37 nm, respectively). These results suggest not only that the novel alpha-conotoxins and EI can operate as nicotinic acetylcholine receptor inhibitors, but also that they bind both alpha(1)beta(1)gammadelta and alpha(4)beta(2) nicotinic acetylcholine receptors with very high affinity and increase their intrinsic cholinergic response. Their unique properties make them excellent tools for studying the toxin-receptor interaction, as well as models with which to design highly specific therapeutic drugs.

Wide phylogenetic distribution of Scorpine and long-chain beta-KTx-like peptides in scorpion venoms: identification of "orphan" components.

Scorpine and toxins specific for potassium channels of the family beta (beta-Ktx) are two types of structurally related scorpion venom components, characterized by an unusually long extended N-terminal segment, followed by a Cys-rich domain with some resemblance to other scorpion toxins. In this communication, we report evidence supporting the ubiquitous presence of Scorpine and beta-KTx-like polypeptides and their precursors in scorpions of the genus Tityus of the family Buthidae, but also included is the first example of such peptides in scorpions from the family Iuridae. Seven new beta-KTxs or Scorpine-like peptides and precursors are reported: five from the genus Tityus (T. costatus, T. discrepans and T. trivittatus) and two from Hadrurus gertschi. The cDNA precursors for all of these peptides were obtained by molecular cloning and their presence in the venoms were confirmed for various peptides. Analysis of the sequences revealed the existence of at least three distinct groups: (1) beta-KTx-like peptides from buthids; (2) Scorpine-like peptides from scorpionid and iurid scorpions; (3) heterogeneous peptides similar to BmTXKbeta of buthids and iurids. The biological function for most of these peptides is not well known; that is why they are here considered "orphan" peptides.

A Deeper Examination of Thorellius atrox Scorpion Venom Components with Omic Techonologies.

This communication reports a further examination of venom gland transcripts and venom composition of the Mexican scorpion Thorellius atrox using RNA-seq and tandem mass spectrometry. The RNA-seq, which was performed with the Illumina protocol, yielded more than 20,000 assembled transcripts. Following a database search and annotation strategy, 160 transcripts were identified, potentially coding for venom components. A novel sequence was identified that potentially codes for a peptide with similarity to spider ω-agatoxins, which act on voltage-gated calcium channels, not known before to exist in scorpion venoms. Analogous transcripts were found in other scorpion species. They could represent members of a new scorpion toxin family, here named omegascorpins. The mass fingerprint by LC-MS identified 135 individual venom components, five of which matched with the theoretical masses of putative peptides translated from the transcriptome. The LC-MS/MS de novo sequencing allowed to reconstruct and identify 42 proteins encoded by assembled transcripts, thus validating the transcriptome analysis. Earlier studies conducted with this scorpion venom permitted the identification of only twenty putative venom components. The present work performed with more powerful and modern omic technologies demonstrates the capacity of accomplishing a deeper characterization of scorpion venom components and the identification of novel molecules with potential applications in biomedicine and the study of ion channel physiology.

Venom gland transcriptomic and venom proteomic analyses of the scorpion Megacormus gertschi Díaz-Najera, 1966 (Scorpiones: Euscorpiidae: Megacorminae).

The soluble venom from the Mexican scorpion Megacormus gertschi of the family Euscorpiidae was obtained and its biological effects were tested in several animal models. This venom is not toxic to mice at doses of 100 µg per 20 g of mouse weight, while being lethal to arthropods (insects and crustaceans), at doses of 20 µg (for crickets) and 100 µg (for shrimps) per animal. Samples of the venom were separated by high performance liquid chromatography and circa 80 distinct chromatographic fractions were obtained from which 67 components have had their molecular weights determined by mass spectrometry analysis. The N-terminal amino acid sequence of seven protein/peptides were obtained by Edman degradation and are reported. Among the high molecular weight components there are enzymes with experimentally-confirmed phospholipase activity. A pair of telsons from this scorpion species was dissected, from which total RNA was extracted and used for cDNA library construction. Massive sequencing by the Illumina protocol, followed by de novo assembly, resulted in a total of 110,528 transcripts. From those, we were able to annotate 182, which putatively code for peptides/proteins with sequence similarity to previously-reported venom components available from different protein databases. Transcripts seemingly coding for enzymes showed the richest diversity, with 52 sequences putatively coding for proteases, 20 for phospholipases, 8 for lipases and 5 for hyaluronidases. The number of different transcripts potentially coding for peptides with sequence similarity to those that affect ion channels was 19, for putative antimicrobial peptides 19, and for protease inhibitor-like peptides, 18. Transcripts seemingly coding for other venom components were identified and described. The LC/MS analysis of a trypsin-digested venom aliquot resulted in 23 matches with the translated transcriptome database, which validates the transcriptome. The proteomic and transcriptomic analyses reported here constitute the first approach to study the venom components from a scorpion species belonging to the family Euscorpiidae. The data certainly show that this venom is different from all the ones described thus far in the literature.

Biochemical and biological activities of the venom of the Chinese pitviper Zhaoermia mangshanensis, with the complete amino acid sequence and phylogenetic analysis of a novel Arg49 phospholipase A2 myotoxin.

Zhaoermia mangshanensis (formerly Trimeresurus mangshanensis, Ermia mangshanensis) represents a monotypic genus of pitviper known only from Mt Mang in China's Hunan Province, and is among the largest and most spectacular of Asian venomous snakes. The venom of Zhaoermia exhibits high coagulant activity on bovine and human fibrinogen and human plasma, high phosphodiesterase and arginine ester hydrolytic activity, and moderate to low l-amino acid oxidase, kallikrein, caseinolytic, phospholipase A(2) (PLA(2)), haemorrhagic and myotoxic activities. The approximate i.p. LD(50) of the venom in mice was estimated to be 4 mg/kg. We purified the major toxin of Zhaoermia venom by gel-filtration, cation-exchange chromatography and HPLC. The toxin, a homodimer with an experimental monomeric mass of 13,972 Da, induced edema and myonecrosis in mice, but was devoid of detectable PLA(2) catalytic activity. Its complete amino acid sequence is composed of 121 amino acid residues cross-linked by seven disulfide bridges, and shows more than 80% identity to two Lys49-PLA(2)s from distantly related Asian pitvipers, Protobothrops mucrosquamatus and Calloselasma rhodostoma. Phylogenetic analysis of the novel toxin, zhaoermiatoxin, confirmed that it is rooted within a comprehensive sample of Lys49-PLA(2)s despite having an arginine residue in position 49, suggesting a secondary Lys49-->Arg substitution which did not alter the catalytic inactivity of the molecule.

Characterization of venom components from the scorpion Androctonus crassicauda of Turkey: peptides and genes.

The soluble venom from the scorpion Androctonus crassicauda was fractionated by high performance liquid chromatography. At least 44 different sub-fractions were resolved and collected for finger print mass analysis using an electrospray mass spectrometer. This analysis revealed the presence of 80 distinct molecular mass components, from which five were further characterized. A peptide, named Acra1 was fully sequenced. It contains 58 amino acid residues cross-bridged by six cysteines forming three disulfide pairs, with a molecular mass of 6497 Da. A second purified peptide named Acra2 was partially sequenced with a molecular mass of 7849 Da. Acra1 is toxic and Acra2 is lethal to mice, at the dose assayed. Additionally, a cDNA library of the venomous gland of one specimen was prepared and several clones were obtained among which is one that codes for Acra1. Three analog gene sequences were found with point mutations either in the section that corresponds to the mature peptide or to the signal peptide. The signal peptide is 22 amino acid residues long. Several other gene sequences obtained suggest the presence in this venom of three distinct groups of peptides, among which are peptides similar to known Na(+)-channel specific toxins of other scorpions. A new type of peptide was identified with odd number of cysteines (seven), allowing the formation of heterodimers with molecular masses in the range of 16,000 atomic mass units (a.m.u.).

Venom Gland Transcriptomic and Proteomic Analyses of the Enigmatic Scorpion Superstitionia donensis (Scorpiones: Superstitioniidae), with Insights on the Evolution of Its Venom Components.

Venom gland transcriptomic and proteomic analyses have improved our knowledge on the diversity of the heterogeneous components present in scorpion venoms. However, most of these studies have focused on species from the family Buthidae. To gain insights into the molecular diversity of the venom components of scorpions belonging to the family Superstitioniidae, one of the neglected scorpion families, we performed a transcriptomic and proteomic analyses for the species Superstitionia donensis. The total mRNA extracted from the venom glands of two specimens was subjected to massive sequencing by the Illumina protocol, and a total of 219,073 transcripts were generated. We annotated 135 transcripts putatively coding for peptides with identity to known venom components available from different protein databases. Fresh venom collected by electrostimulation was analyzed by LC-MS/MS allowing the identification of 26 distinct components with sequences matching counterparts from the transcriptomic analysis. In addition, the phylogenetic affinities of the found putative calcins, scorpines, La1-like peptides and potassium channel κ toxins were analyzed. The first three components are often reported as ubiquitous in the venom of different families of scorpions. Our results suggest that, at least calcins and scorpines, could be used as molecular markers in phylogenetic studies of scorpion venoms.

A Comprehensive Proteomic Study of the Skin Secretions of the Frog Lithobates spectabilis.

Disulfide C-terminal loop fragments derived from AMPs and the presence of peptidases have been previously reported in the skin secretions of different amphibians. However, there are only a few studies on the identification of enzymes in frog skin secretion based on the primary structure of these proteins. Similarly, little data exist regarding the identification of disulfide C-terminal loops at large scale. Therefore, a comprehensive study on this issue certainly could bring in much more information for understanding this molecular process and its biochemical consequences. Thus, the aim of this work was to characterize the presence of disulfide C-terminal loop fragments of AMPs and identify the proteins and probable enzymes present in the completely unknown secretion contents of the frog Lithobates spectabilis. For this purpose, high-resolution mass spectrometry was applied to analyze the skin secretions processed by two different protocols: (1) using a cocktail of enzymatic inhibitors and 2) without any protease inhibitors, maintaining the solution for 2 hours at 10°C. Results from procedure-1, revealed 122 molecular masses, whereas procedure-2 permitted 253 different molecular masses to be identified. Fifty-nine peptides including 22 disulfide C-terminal loop-containing peptides were obtained following procedure-2. Polyacrylamide gel electrophoresis separation, tryptic digestion and LCMS/ MS were used for "de novo" sequencing of 111 different peptides and the unequivocal identification of fifteen proteins including at least three different peptidases. Additionally, it was possible to fully sequence eight peptides, including a ranatuerin-related peptide identified here as Spectabilin, that was subsequently chemically synthesized and showed high antibacterial, antiparasitic and cytotoxic activities.

Two novel toxins from the Amazonian scorpion Tityus cambridgei that block Kv1.3 and Shaker B K(+)-channels with distinctly different affinities.

Two novel toxic peptides (Tc30 and Tc32) were isolated and characterized from the venom of the Brazilian scorpion Tityus cambridgei. The first have 37 and the second 35 amino acid residues, with molecular masses of 3,871.8 and 3,521.5, respectively. Both contain three disulfide bridges but share only 27% identity. They are relatively potent inhibitors of K(+)-currents in human T lymphocytes with K(d) values of 10 nM for Tc32 and 16 nM for Tc30, but they are less potent or quite poor blockers of Shaker B K(+)-channels, with respective K(d) values of 74 nM and 4.7 microM. Tc30 has a lysine in position 27 and a tyrosine at position 36 identical to those of charybdotoxin. These two positions conform the dyad considered essential for activity. On the contrary, Tc32 has a serine in the position equivalent to lysine 27 of charybdotoxin and does not contain any aromatic amino acid. Due to its unique primary sequence and to its distinctive preference for K(+)-channels of T lymphocytes, it was classified as the first example of a new subfamily of K(+)-channel-specific peptides (alpha-KT x 18.1). Tc30 is a member of the Tityus toxin II-9 subfamily and was given the number alpha-KT x 4.4.

Inhibition of the collapse of the Shaker K+ conductance by specific scorpion toxins.

The Shaker B K(+) conductance (G(K)) collapses when the channels are closed (deactivated) in Na(+) solutions that lack K(+) ions. Also, it is known that external TEA (TEA(o)) impedes the collapse of G(K), and that channel block by TEA(o) and scorpion toxins are two mutually exclusive events. Therefore, we tested the ability of scorpion toxins to inhibit the collapse of G(K) in 0 K(+). We have found that these toxins are not uniform regarding the capacity to protect G(K). Those toxins, whose binding to the channels is destabilized by external K(+), are also effective inhibitors of the collapse of G(K). In addition to K(+), other externally added cations also destabilize toxin block, with an effectiveness that does not match the selectivity sequence of K(+) channels. The inhibition of the drop of G(K) follows a saturation relationship with [toxin], which is fitted well by the Michaelis-Menten equation, with an apparent Kd bigger than that of block of the K(+) current. However, another plausible model is also presented and compared with the Michaelis-Menten model. The observations suggest that those toxins that protect G(K) in 0 K(+) do so by interacting either with the most external K(+) binding site of the selectivity filter (suggesting that the K(+) occupancy of only that site of the pore may be enough to preserve G(K)) or with sites capable of binding K(+) located in the outer vestibule of the pore, above the selectivity filter.