The Experts below are selected from a list of 501 Experts worldwide ranked by ideXlab platform
Michael E. Adams - One of the best experts on this subject based on the ideXlab platform.
-
Heterodimeric Structure of the Spider Toxin o-Agatoxin IA Revealed by Precursor Analysis and Mass Spectrometry*
2008Co-Authors: Ameurfina D. Santos$$y, Michael E. Adams, Julita S. Imperial, Tanuja Chaudharyl, Ronald C. Beavis, Brian T. Chait, John P. Hunspergers, Baldomero M. Oliveras, David R. HillyardAbstract:We report the first molecular characterization of a In the funnel web spider, Agelenopsis Aperta, a large variety precursor sequence for a small, Ca2+ channel blocking, of small polypeptide toxins are present. Two general classes peptide spider toxin, w-agatoxin IA. By integrating have been identified, the p-agatoxins (Skinner et al., 1989), information generated from a molecular genetic ap- which activate Na2+ channels at the insect neuromuscular proach using agatoxin cDNAs with data provided from junction (Adams et al., 1989), and the w-agatoxins. The w-mass spectrometry of the mature toxin, we were able agatoxins specifically inhibit voltage-sensitive Ca2+ channels to deduce the likely mechanisms by which the toxin (Adams et al., 1990; Scott et al., 1990; Mintz et al., 1991,1992; precursor peptide is processed to its mature heterodi- Venema et al., 1992). Four different classes of w-agatoxins meric form. A particularly interesting feature of the have been described, each with divergent biochemical charprepropeptide is the occurrence of two glutamate-rich acteristics and pharmacological specificity (Olivera et al., sequences interposed between the signal sequences, the major peptide toxin, and the minor toxin peptide. Ex-1991; Adams et al., 1992). The first of these to be charactercisio
-
Agatoxins: ion channel specific toxins from the American funnel web spider, Agelenopsis Aperta.
Toxicon : official journal of the International Society on Toxinology, 2004Co-Authors: Michael E. AdamsAbstract:Agatoxins from Agelenopsis Aperta venom target three classes of ion channels, including transmitter-activated cation channels, voltage-activated sodium channels, and voltage-activated calcium channels. The α-agatoxins are non-competitive, use-dependent antagonists of glutamate receptor channels, and produce rapid but reversible paralysis in insect prey. Their actions are facilitated by the μ-agatoxins, which shift voltage-dependent activation of neuronal sodium channels to more negative potentials, causing spontaneous transmitter release and repetitive action potentials. The ω-agatoxins target neuronal calcium channels, modifying their properties in distinct ways, either through gating modification (ω-Aga-IVA) or by reduction of unitary current (ω-Aga-IIIA). The α-agatoxins and ω-agatoxins modify both insect and vertebrate ion channels, while the μ-agatoxins are selective for insect channels. Agatoxins have been used as selective pharmacological probes for characterization of ion channels in the brain and heart, and have been evaluated as candidate biopesticides.
-
The solution structure of ω-Aga-IVB, a P-type calcium channel antagonist from venom of the funnel web spider, Agelenopsis Aperta
Journal of Biomolecular NMR, 1995Co-Authors: Michael D. Reily, Venkataraman Thanabal, Michael E. AdamsAbstract:The 48 amino acid peptides ω-Aga-IVA and ω-Aga-IVB are the first agents known to specifically block P-type calcium channels in mammalian brain, thus complementing the existing suite of pharmacological tools used for characterizing calcium channels. These peptides provide a new set of probes for studies aimed at elucidating the structural basis underlying the subtype specificity of calcium channel antagonists. We used 288 NMR-derived constraints in a protocol combining distance geometry and molecular dynamics employing the program DGII, followed by energy minimization with Discover to derive the three-dimensional structure of ω-Aga-IVB. The toxin consists of a well-defined core region, comprising seven solvent-shielded residues and a well-defined triple-stranded β-sheet. Four loop regions have average backbone rms deviations between 0.38 and 1.31 Å, two of which are well-defined type-II β-turns. Other structural features include disordered C- and N-termini and several conserved basic amino acids that are clustered on one face of the molecule. The reported structure suggests a possible surface for interaction with the channel. This surface contains amino acids that are identical to those of another known P-type calcium channel antagonist, ω-Aga-IVA, and is rich in basic residues that may have a role in binding to the anionic sites in the extracellular regions of the calcium channel.
-
The solution structure of omega-Aga-IVB, a P-type calcium channel antagonist from venom of the funnel web spider, Agelenopsis Aperta.
Journal of biomolecular NMR, 1995Co-Authors: Michael D. Reily, Venkataraman Thanabal, Michael E. AdamsAbstract:The 48 amino acid peptides ω-Aga-IVA and ω-Aga-IVB are the first agents known to specifically block P-type calcium channels in mammalian brain, thus complementing the existing suite of pharmacological tools used for characterizing calcium channels. These peptides provide a new set of probes for studies aimed at elucidating the structural basis underlying the subtype specificity of calcium channel antagonists. We used 288 NMR-derived constraints in a protocol combining distance geometry and molecular dynamics employing the program DGII, followed by energy minimization with Discover to derive the three-dimensional structure of ω-Aga-IVB. The toxin consists of a well-defined core region, comprising seven solvent-shielded residues and a well-defined triple-stranded β-sheet. Four loop regions have average backbone rms deviations between 0.38 and 1.31 A, two of which are well-defined type-II β-turns. Other structural features include disordered C- and N-termini and several conserved basic amino acids that are clustered on one face of the molecule. The reported structure suggests a possible surface for interaction with the channel. This surface contains amino acids that are identical to those of another known P-type calcium channel antagonist, ω-Aga-IVA, and is rich in basic residues that may have a role in binding to the anionic sites in the extracellular regions of the calcium channel.
-
Toxityping rat brain calcium channels with omega-toxins from spider and cone snail venoms.
Biochemistry, 1993Co-Authors: Michael E. Adams, Julita S. Imperial, Richard A. Myers, Baldomero M. OliveraAbstract:Different types of voltage-sensitive Ca2+ channels in the brain can be defined by specific ligands: L-type Ca2+ channels are uniquely sensitive to dihydropyridines, and N-type Ca2+ channels are selectively blocked by the Conus peptide omega-CTX-GVIA. Cloning data have revealed additional calcium channel types in mammalian brain for which selective ligands would be desirable. We describe binding experiments involving three newer ligands that block dihydropyridine- and omega-CTX-GVIA-resistant Ca channels: omega-Aga-IIIA and omega-Aga-IVA from venom of the spider Agelenopsis Aperta and omega-CTX-MVIIC from Conus magus. [125I]omega-Aga-IVA binds with high affinity (IC50 = approximately 50 nM) to receptors in rat brain which may correspond to P-like calcium channels. A second high-affinity site (IC50 = approximately 1 nM) is defined by [125I]omega-CTX-MVIIC, proposed here to be on an "O"-type calcium channel. [125I]omega-Aga-IIIA targets homologous binding sites present on multiple Ca channel types. The IIIA sites overlap with the binding sites for [125I]omega-CTX-GVIA and [125I]omega-CTX-MVIIC. The IIIA sites do not overlap with the site defined by omega-Aga-IVA. Thus toxin ligands may be highly specific for a particular Ca channel (i.e., GVIA for the N-type channel) or exhibit broader specificity (i.e., omega-Aga-IIIA, which appears to bind L-, N-, P-, and O-type Ca2+ channels).
Susan E. Riechert - One of the best experts on this subject based on the ideXlab platform.
-
In the spider nursery: indifference, cooperation or antagonism?
Journal of Arachnology, 2017Co-Authors: Susan E. Riechert, Jonathan N. Pruitt, Jennifer M. BoscoAbstract:Based on studies of adult behavior, the desert spider Agelenopsis Aperta (Gertsch, 1934) is considered exemplary of a species exhibiting an aggressive syndrome. This study offers a first examination of the nature of interactions that juvenile A. Aperta engage in during the period when sibs are clustered on a group web. We test the hypothesis that early instar A. Aperta lack the aggressiveness noted for older instars. Our data set is comprised of observations of five weekly feedings offered to 818 sibling pairs, constituting an average of 4.6 replicate sib pairs from each of 174 families. At each weekly feeding, a worker termite was offered to each sib in the shared container in which they had built web retreats. We observed no cooperative foraging during the course of these feedings. Rather, most families exhibited a mix of independent foraging and non-injurious contests over prey. We present a brief overview of the occurrence and initiation of contests over prey, with particular reference to the weekly feeding in which contests first occur versus the feeding in which a seminal contest takes place (i.e., where sibs earn permanent winner versus loser status).
-
Molecular evidence for Pleistocene glacial cycles driving diversification of a North American desert spider, Agelenopsis Aperta.
Molecular ecology, 2004Co-Authors: Nadia A. Ayoub, Susan E. RiechertAbstract:The influence of historical climatic vs. geological changes on species diversification patterns was investigated in a widely distributed North American desert spider, Agelenopsis Aperta (Araneae: Agelenidae), with particular reference to Pleistocene glacial cycles and earlier patterns of mountain building. Levels of sequence divergence obtained from the mitochondrial gene, cytochrome oxidase I, dated to the Pleistocene, eliminating Rocky Mountain orogeny as a cause of diversification, as orogeny ended 4 million years ago. The results of phylogenetic and network analyses showed the presence of three geographically defined clades, which were consistent with the presence of at least three glacial refugia: (i) east of the Rocky Mountains; (ii) between the Rocky Mountains and Sierra Nevadas; and (iii) west of the Sierra Nevadas. In addition, populations within the Rocky Mountains exhibited significantly lower genetic diversity than populations east of the Rocky Mountains and the haplotypes found within the Rockies were a subset of eastern haplotypes. These patterns suggest that a post-Pleistocene range expansion occurred out of an eastern glacial refugium into the Rocky Mountains. Examination of phylogeographical studies of other North American desert taxa indicated that mountain building explained diversification patterns more effectively for some taxa but Pleistocene climate change was more important for others, including A. Aperta.
-
Do female spiders select heavier males for the genes for behavioral aggressiveness they offer their offspring
Evolution; international journal of organic evolution, 2003Co-Authors: Susan E. Riechert, Philip M. JohnsAbstract:We explore the hypothesis that females choose to mate with heavier males for the genes for behavioral aggressiveness they offer their offspring in the desert spider, Agelenopsis Aperta. Behavioral aggressiveness is important to competition for limited resources in the field and is thus correlated with the mass spiders achieve. We established four crosses based on the body mass relationships of parents subjected to selection in their natural environment (female mass/male mass: HI/HI, HI/LO, LO/HI, and LO/LO) and reared the F1 offspring in a noncompetitive laboratory environment. Offspring size and mass at maturity were measured, life history parameters recorded, and behavioral aggressiveness scored in a series of tests. Significant familial effects were detected in all of these measures, but pertinent cross effects were observed only in the assays measuring behavioral aggressiveness. The results were summarized in terms of the fitness costs to HI females of mating with LO males (fewer female offspring of the more aggressive phenotypes) and the benefits to LO females of mating with HI males (fewer fearful offspring of both sexes).
-
Superfluous killing in spiders: a consequence of adaptation to food-limited environments?
Behavioral Ecology, 2001Co-Authors: Jennifer L. Maupin, Susan E. RiechertAbstract:The hypothesis that superfluous killing, partial consumption, and abandonment of prey is a consequence of adaptation to foodlimited environments was tested in two feeding trials on a desert spider, Agelenopsis Aperta. First, we made comparisons among populations inhabiting sites of high prey (HP) or low prey (LP) availability that differed in their degree of genetic isolation. Typically, A. Aperta entirely consumed one or two of the prey items it captured in a feeding bout. Additional prey were partially consumed or abandoned without eating. Spiders from the genetically isolated HP population, however, captured fewer prey and showed a higher incidence of full feeding on prey than did individuals from the other populations. Only one spider from this population captured a prey item that it failed to feed on, whereas spiders from LP populations failed to feed on high numbers of captured prey. The greatest variability in feeding behavior was exhibited in the HP population that experienced gene flow. The second test was based on the finding that aggressiveness is largely a sex-linked trait in A. Aperta: the aggressiveness of the female parent only is inherited by male offspring, whereas both parents contribute to this trait in female offspring. All female F1 hybrids between LP and HP parental types exhibited high levels of superfluous killing, as did male F1 hybrids derived from LP females. F1 hybrid males derived from HP females exhibited extremely low levels of superfluous killing. Superfluous killing thus has its basis in the genetic control of levels of aggression.
-
Superfluous killing in spiders: a consequence of adaptation to food-limited environments
2001Co-Authors: Jennifer L. Maupin, Susan E. RiechertAbstract:The hypothesis that superfluous killing, partial consumption, and abandonment of prey is a consequence of adaptation to food-limited environments was tested in two feeding trials on a desert spider, Agelenopsis Aperta. First, we made comparisons among populations inhabiting sites of high prey (HP) or low prey (LP) availability that differed in their degree of genetic isolation. Typically, A. Aperta entirely consumed one or two of the prey items it captured in a feeding bout. Additional prey were partially consumed or abandoned without eating. Spiders from the genetically isolated HP population, however, captured fewer prey and showed a higher incidence of full feeding on prey than did individuals from the other populations. Only one spider from this population captured a prey item that it failed to feed on, whereas spiders from LP populations failed to feed on high numbers of captured prey. The greatest variability in feeding behavior was exhibited in the HP population that experienced gene flow. The second test was based on the finding that aggressiveness is largely a sex-linked trait in A. Aperta: the aggressiveness of the female parent only is inherited by male offspring, whereas both parents contribute to this trait in female offspring. All female F1 hybrids between LP and HP parental types exhibited high levels of superfluous killing, as did male F1 hybrids derived from LP females. F1 hybrid males derived from HP females exhibited extremely low levels of superfluous killing. Superfluous killing thus has its basis in the genetic control of levels of aggression. Key words: Agelenopsis Aperta, behavioral variation, genetic determination, predation, predator populations, spiders, superfluous killing. [Behav Ecol 12:569–576 (2001)] Geographically isolated populations often have evolvedinto distinct ecotypes that differ in morphological, lif
Bruce P Bean - One of the best experts on this subject based on the ideXlab platform.
-
Structure and properties of omega-agatoxin IVB, a new antagonist of P-type calcium channels.
Molecular pharmacology, 1993Co-Authors: Michael E. Adams, Isabelle M Mintz, M.d. Reily, V. Thanabal, Bruce P BeanAbstract:A new peptide antagonist of voltage-activated calcium channels was purified from venom of the funnel web spider, Agelenopsis Aperta. This 48-amino acid peptide, omega-agatoxin (omega-Aga)-IVB, was found to be a potent (Kd, approximately 3 nM) blocker of P-type calcium channels in rat cerebellar Purkinje neurons but had no activity against T-type, L-type, or N-type calcium channels in a variety of neurons. The calcium channel-blocking properties of omega-Aga-IVB were similar to those of another toxin, omega-Aga-IVA, which has 71% amino acid identity with omega-Aga-IVB. The 10-fold greater abundance of omega-Aga-IVB in venom allowed structural studies using NMR spectroscopy. The three-dimensional structure derived from NMR data resulted in a proposed disulfide bond configuration for the peptide. Although omega-Aga-IVB has fewer basic and more acidic residues than does omega-Aga-IVA, the two toxins show conservation of positively charged residues in a mid-peptide region that is predicted to form one face of the omega-Aga-IVB molecule. This region may be crucial for high affinity binding to the P-type calcium channel. In contrast, the amino termini of the two toxins have different charges and seem unlikely to be involved in binding to the channel.
-
Block of calcium channels in rat neurons by synthetic ω-Aga-IVA
Neuropharmacology, 1993Co-Authors: Isabelle M Mintz, Bruce P BeanAbstract:We investigated block of voltage-dependent Ca channels in freshly dissociated rat central and peripheral neurons by the synthetic peptide ω-Aga-IVA. Synthetic ω-Aga-IVA blocked ∼90% of the high-threshold Ca current in cerebellar Purkinje neurons with an estimated Kd of ∼ 1.5 nM, slightly higher than that determined for block by toxin purified from Agelenopsis Aperta venom. At 200 nM, the synthetic peptide blocked a small fraction of current in dorsal root ganglion neurons but had no effect on identified components of current carried by low-threshold T-type channels or by dihydropyridine-sensitive L-type Ca channels. Up to 800 nM synthetic peptide had no effect on the current in sympathetic neurons, carried mainly by ω-conotoxin GVIA-sensitive N-type channels. In spinal cord neurons, the same fraction of high-threshold current was blocked by synthetic peptide or purified toxin. We conclude that synthetic ω-Aga-IVA has the same high selectivity for blocking P-type Ca channels as does toxin purified from spider venom.
-
inhibition of n and l type ca2 channels by the spider venom toxin omega aga iiia
Proceedings of the National Academy of Sciences of the United States of America, 1991Co-Authors: Isabelle M Mintz, Michael E. Adams, Virginia J. Venema, Bruce P BeanAbstract:Abstract omega-Aga-IIIA, an 8.5-kDa peptide toxin isolated from the venom of Agelenopsis Aperta, was found to be a highly potent inhibitor of Ca channels in cardiac muscle and in peripheral and central neurons of rats and frogs. Cardiac L-type Ca channels were completely (Kd approximately 0.6 nM) blocked by omega-Aga-IIIA. In sensory neurons, the toxin inhibited most high-threshold Ca current but not T-type Ca current. omega-Aga-IIIA blocked with similar potency (Kd approximately 1.5 nM) both omega-conotoxin GVIA-sensitive and dihydropyridine-sensitive current components but left a fraction (approximately 35%) of high-threshold current that was also resistant to omega-conotoxin and dihydropyridines. The toxin blocks N- and L-type channels with equal potency and therefore may identify a high-affinity binding site common to these two Ca channel types.
Isabelle M Mintz - One of the best experts on this subject based on the ideXlab platform.
-
Structure and properties of omega-agatoxin IVB, a new antagonist of P-type calcium channels.
Molecular pharmacology, 1993Co-Authors: Michael E. Adams, Isabelle M Mintz, M.d. Reily, V. Thanabal, Bruce P BeanAbstract:A new peptide antagonist of voltage-activated calcium channels was purified from venom of the funnel web spider, Agelenopsis Aperta. This 48-amino acid peptide, omega-agatoxin (omega-Aga)-IVB, was found to be a potent (Kd, approximately 3 nM) blocker of P-type calcium channels in rat cerebellar Purkinje neurons but had no activity against T-type, L-type, or N-type calcium channels in a variety of neurons. The calcium channel-blocking properties of omega-Aga-IVB were similar to those of another toxin, omega-Aga-IVA, which has 71% amino acid identity with omega-Aga-IVB. The 10-fold greater abundance of omega-Aga-IVB in venom allowed structural studies using NMR spectroscopy. The three-dimensional structure derived from NMR data resulted in a proposed disulfide bond configuration for the peptide. Although omega-Aga-IVB has fewer basic and more acidic residues than does omega-Aga-IVA, the two toxins show conservation of positively charged residues in a mid-peptide region that is predicted to form one face of the omega-Aga-IVB molecule. This region may be crucial for high affinity binding to the P-type calcium channel. In contrast, the amino termini of the two toxins have different charges and seem unlikely to be involved in binding to the channel.
-
Block of calcium channels in rat neurons by synthetic ω-Aga-IVA
Neuropharmacology, 1993Co-Authors: Isabelle M Mintz, Bruce P BeanAbstract:We investigated block of voltage-dependent Ca channels in freshly dissociated rat central and peripheral neurons by the synthetic peptide ω-Aga-IVA. Synthetic ω-Aga-IVA blocked ∼90% of the high-threshold Ca current in cerebellar Purkinje neurons with an estimated Kd of ∼ 1.5 nM, slightly higher than that determined for block by toxin purified from Agelenopsis Aperta venom. At 200 nM, the synthetic peptide blocked a small fraction of current in dorsal root ganglion neurons but had no effect on identified components of current carried by low-threshold T-type channels or by dihydropyridine-sensitive L-type Ca channels. Up to 800 nM synthetic peptide had no effect on the current in sympathetic neurons, carried mainly by ω-conotoxin GVIA-sensitive N-type channels. In spinal cord neurons, the same fraction of high-threshold current was blocked by synthetic peptide or purified toxin. We conclude that synthetic ω-Aga-IVA has the same high selectivity for blocking P-type Ca channels as does toxin purified from spider venom.
-
inhibition of n and l type ca2 channels by the spider venom toxin omega aga iiia
Proceedings of the National Academy of Sciences of the United States of America, 1991Co-Authors: Isabelle M Mintz, Michael E. Adams, Virginia J. Venema, Bruce P BeanAbstract:Abstract omega-Aga-IIIA, an 8.5-kDa peptide toxin isolated from the venom of Agelenopsis Aperta, was found to be a highly potent inhibitor of Ca channels in cardiac muscle and in peripheral and central neurons of rats and frogs. Cardiac L-type Ca channels were completely (Kd approximately 0.6 nM) blocked by omega-Aga-IIIA. In sensory neurons, the toxin inhibited most high-threshold Ca current but not T-type Ca current. omega-Aga-IIIA blocked with similar potency (Kd approximately 1.5 nM) both omega-conotoxin GVIA-sensitive and dihydropyridine-sensitive current components but left a fraction (approximately 35%) of high-threshold current that was also resistant to omega-conotoxin and dihydropyridines. The toxin blocks N- and L-type channels with equal potency and therefore may identify a high-affinity binding site common to these two Ca channel types.
Manabu Kuwada - One of the best experts on this subject based on the ideXlab platform.
-
structural analysis of n linked carbohydrate chains of funnel web spider Agelenopsis Aperta venom peptide isomerase
Bioscience Biotechnology and Biochemistry, 1998Co-Authors: Yasushi Shikata, Hiroshi Ohe, Nariyasu Mano, Manabu Kuwada, Naoki AsakawaAbstract:The structure of the N-linked carbohydrate chains of peptide isomerase from the venom of the funnel web spider (Agelenopsis Aperta) has been analyzed. Carbohydrates were released from peptide isomerase by hydrazinolysis and reductively aminated with 2-aminopyridine. The fluorescent derivatives were purified by phenol/chloroform extraction, followed by size-exclusion HPLC. The structure of the purified pyridylamino (PA-) carbohydrate chains were analyzed by a combination of two-dimensional HPLC mapping, sugar composition analysis, sequential exoglycosidase digestions, and mass spectrometry. The peptide isomerase contains six kinds of N-linked carbohydrate chains of truncated high-mannose type, with a fucose α1-6 linked to the reducing N-acetylglucosamine in approximately 80% of them.
-
isolation and characterization of a peptide isomerase from funnel web spider venom
Journal of Biological Chemistry, 1995Co-Authors: Yasushi Shikata, Tetsuyuki Teramoto, Yukio Nishizawa, Kouichi Katayama, Tomohiro Watanabe, Atsushi Inoue, Yoshiyuki Kawakami, Manabu KuwadaAbstract:Abstract A novel peptide isomerase was purified from the venom of funnel web spider, Agelenopsis Aperta. The complete primary structure of the isomerase has been established by sequence analyses of polypeptide chains, assignments of disulfide bridges, carbohydrate analyses, and mass spectrometry of sugar chains. The isomerase was found to be a 29-kDa polypeptide that consists of an 18-residue light chain and a 243-residue heavy chain connected by a single disulfide bridge. The heavy chain contains three intramolecular disulfide bridges and one N-linked oligosaccharide chain with a simple trimannosyl core structure. A sequence homology search showed a significant similarity of the enzyme with serine proteases, particularly around a putative catalytic triad of the isomerase. The isomerase specifically interconverts the configuration of Ser of a 48-amino-acid peptide, -agatoxin-TK, and the conversion rate from L-Ser to D-Ser was approximately two times faster than the reverse reaction.
-
Omega-agatoxin-TK containing D-serine at position 46, but not synthetic omega-[L-Ser46]agatoxin-TK, exerts blockade of P-type calcium channels in cerebellar Purkinje neurons.
Molecular pharmacology, 1994Co-Authors: Manabu Kuwada, K. Y. Kumagaye, Tetsuyuki Teramoto, Tetsuhiro Niidome, Kohei Sawada, Tomohiro Watanabe, K. Nakajima, T Kawai, Y Kawakami, Y NishizawaAbstract:omega-Agatoxin-TK (omega-Aga-TK), a 48-amino-acid peptide isolated from the venom of the funnel web spider (Agelenopsis Aperta), is a selective and potent inhibitor of P-type calcium channels in the nervous system. We have synthesized a peptide that has the amino acid sequence identified for native omega-Aga-TK. The synthetic omega-Aga-TK, however, showed 80-90-fold less potent inhibition of P-type calcium channels, compared with native omega-Aga-TK. Enantiomer analysis of native omega-Aga-TK revealed D-serine at position 46, and synthetic omega-[D-Ser46]Aga-TK had the same potency as native omega-Aga-TK for blocking P-type calcium channels in cultured cerebellar Purkinje neurons. Two peptide fragments of omega-Aga-TK, namely omega-Aga-TK(1-43) and the carboxyl-terminal peptide fragment omega-Aga-TK(44-48), did not produce any significant inhibition of P-type calcium channels or interfere with the blockade of the channels elicited by native omega-Aga-TK. Molecular dynamics calculations showed that the carboxyl-terminal, six-amino-acid peptide of omega-Aga-TK containing D-Ser46 assumes a different conformation than does the peptide containing L-Ser46. These results suggest that the specific conformation of the carboxyl-terminal region of omega-Aga-TK, particularly the configuration of Ser46, together with a beta-sheet structure formed by four disulfide bonds, might be essential for blockade of P-type calcium channels.
-
a novel peptide from funnel web spider venom ω aga tk selectively blocks p type calcium channels
Biochemical and Biophysical Research Communications, 1993Co-Authors: Tetsuyuki Teramoto, Manabu Kuwada, Tetsuhiro Niidome, Kohei Sawada, Yukio Nishizawa, Kouichi KatayamaAbstract:In the course of purification of ω-Aga-IVA, a specific P-type calcium channel blocker, from the venom of Agelenopsis Aperta we discovered a novel peptide. This peptide, named ω-agatoxin Tsukuba (ω-Aga-TK), also blocked P-type channels and was twelve times more abundant in the venom than ω-Aga-IVA. ω-Aga-TK was purified to homogeneity by a two-step reverse-phase HPLC procedure. Its amino acid sequence is 71% identical to that of ω-Aga-IVA. ω-Aga-TK has a negatively charged N-terminus, whereas ω-Aga-IVA has a positively charged one. Electrophysiological data indicate that ω-Aga-TK is a potent and selective inhibitor of P-type channels.
