The Experts below are selected from a list of 189 Experts worldwide ranked by ideXlab platform
John W Crabb - One of the best experts on this subject based on the ideXlab platform.
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Pseudechetoxin: A peptide blocker of cyclic nucleotide-gated ion channels
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: R. Lane Brown, Karen A West, Tammie L. Haley, John W CrabbAbstract:Ion channels activated by the binding of cyclic nucleotides first were discovered in retinal rods where they generate the cell’s response to light. In other systems, however, it has been difficult to unambiguously determine whether cyclic nucleotide-dependent processes are mediated by protein kinases, their classical effector enzymes, or cyclic nucleotide-gated (CNG) ion channels. Part of this difficulty has been caused by the lack of specific pharmacological tools. Here we report the purification from the venom of the Australian King Brown snake of a peptide toxin that inhibits current through CNG channels. This toxin, which we have named Pseudechetoxin (PsTx), was purified by cation exchange and RP-HPLC and has a molecular mass of about 24 kDa. When applied to the extracellular face of membrane patches containing the α-subunit of the rat olfactory CNG channel, PsTx blocked the cGMP-dependent current with a Ki of 5 nM. Block was independent of voltage and required only a single molecule of toxin. PsTx also blocked CNG channels containing the bovine rod α-subunit with high affinity (100 nM), but it was less effective on the heteromeric version of the rod channel (Ki ≈ 3 μM). We have obtained N-terminal and partial internal sequence data and the amino acid composition of PsTx. These data indicate that PsTx is a basic protein that exhibits some homology with helothermine, a toxin isolated from the venom of the Mexican Beaded Lizard. PsTx promises to be a valuable pharmacological tool for studies on the structure and physiology of CNG channels.
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pseudechetoxin a peptide blocker of cyclic nucleotide gated ion channels pseudechis australis australian king brown snakeypeptide toxinsysnake venomypatch clamp techniqueypeptide sequencing
1999Co-Authors: Lane R Brown, Ammie T L Haley, Karen A West, John W CrabbAbstract:Ion channels activated by the binding of cyclic nucleotides first were discovered in retinal rods where they generate the cell's response to light. In other systems, however, it has been difficult to unambiguously determine whether cyclic nucleotide-dependent processes are mediated by protein kinases, their classical effector enzymes, or cyclic nucleotide-gated (CNG) ion channels. Part of this difficulty has been caused by the lack of specific pharmacological tools. Here we report the purification from the venom of the Australian King Brown snake of a peptide toxin that inhibits current through CNG channels. This toxin, which we have named Pseudechetoxin (PsTx), was purified by cation ex- change and RP-HPLC and has a molecular mass of about 24 kDa. When applied to the extracellular face of membrane patches containing the a-subunit of the rat olfactory CNG channel, PsTx blocked the cGMP-dependent current with a Ki of 5 nM. Block was independent of voltage and required only a single molecule of toxin. PsTx also blocked CNG channels containing the bovine rod a-subunit with high affinity (100 nM), but it was less effective on the heteromeric version of the rod channel (Ki ' 3 mM). We have obtained N-terminal and partial internal sequence data and the amino acid composi- tion of PsTx. These data indicate that PsTx is a basic protein that exhibits some homology with helothermine, a toxin isolated from the venom of the Mexican Beaded Lizard. PsTx promises to be a valuable pharmacological tool for studies on the structure and physiology of CNG channels.
Christopher Shaw - One of the best experts on this subject based on the ideXlab platform.
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Helokinestatin-7 peptides from the venoms of Heloderma Lizards
Peptides, 2012Co-Authors: Hui Wang, Tianbao Chen, Lei Wang, Mei Zhou, Gemma Lowe, Yingqi Zhang, Christopher ShawAbstract:Abstract Helokinestatins 1–6 constitute a family of bradykinin antagonist peptides originally isolated from the venoms of the Gila Monster, Heloderma suspectum and the Mexican Beaded Lizard, Heloderma horridum. Here we report the identification, isolation and preliminary pharmacological characterization of two novel tridecapeptides, named helokinestatin-7S (FDDDSTELILEPR – 1550 Da) and helokinestatin-7H (FDDDSRKLILEPR – 1604 Da), whose primary structures were predicted from cDNAs cloned from venom libraries of respective Heloderma Lizards. Computed molecular masses of putative helokinestatin-7 peptides were used as tools to locate these peptides in archived LC/MS fractions from respective venoms and sequences were confirmed by MS/MS fragmentation. A synthetic replicate of helokinestatin-7H was found to antagonize the relaxation effect of bradykinin on rat arterial smooth muscle but to have no measurable effects alone. In contrast, synthetic helokinestatin-7S was found to directly contract this preparation. Studies on related natural peptides with subtle differences in primary structure can provide the tools for structure/activity studies in pharmacological investigations directed toward unraveling the molecular basis of venom toxicity and for the evaluation of potential therapeutic leads.
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The natriuretic peptide/helokinestatin precursor from Mexican Beaded Lizard (Heloderma horridum) venom: Amino acid sequence deduced from cloned cDNA and identification of two novel encoded helokinestatins☆
Peptides, 2011Co-Authors: Mu Yang, Tianbao Chen, Lei Wang, Mei Zhou, Anwei Ding, Christopher ShawAbstract:Abstract Natriuretic peptides are common components of reptile venoms and molecular cloning of their biosynthetic precursors has revealed that in snakes, they co-encode bradykinin-potentiating peptides and in venomous Lizards, some co-encode bradykinin inhibitory peptides such as the helokinestatins. The common natriuretic peptide/helokinestatin precursor of the Gila Monster, Heloderma suspectum, encodes five helokinestatins of differing primary structures. Here we report the molecular cloning of a natriuretic peptide/helokinestatin precursor cDNA from a venom-derived cDNA library of the Mexican Beaded Lizard (Heloderma horridum). Deduction of the primary structure of the encoded precursor protein from this cloned cDNA template revealed that it consisted of 196 amino acid residues encoding a single natriuretic peptide and five helokinestatins. While the natriuretic peptide was of identical primary structure to its Gila Monster (H. suspectum) homolog, the encoded helokinestatins were not, with this region of the common precursor displaying some significant differences to its H. suspectum homolog. The helokinestatin-encoding region contained a single copy of helokinestatin-1, 2 copies of helokinestatin-3 and single copies of 2 novel peptides, (Phe)5-helokinestatin-2 (VPPAFVPLVPR) and helokinestatin-6 (GPPFNPPPFVDYEPR). All predicted peptides were found in reverse phase HPLC fractions of the same venom. Synthetic replicates of both novel helokinestatins were found to antagonize the relaxing effect of bradykinin on rat tail artery smooth muscle. Thus Lizard venom continues to provide a source of novel biologically active peptides.
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Isolation and cloning of exendin precursor cDNAs from single samples of venom from the Mexican Beaded Lizard (Heloderma horridum) and the Gila monster (Heloderma suspectum).
Toxicon, 2006Co-Authors: Tianbao Chen, Hang Fai Kwok, Craig Ivanyi, Christopher ShawAbstract:Reptile venoms are complex cocktails of bioactive molecules, including peptides. While the drug discovery potential of most species remains unrealized, many are endangered and afforded protection under international treaties. In this study, we describe how potential clinically important bioactive peptides and their corresponding mRNAs can be structurally characterized from single, small samples of reptile venom. The potential type-2 diabetes therapeutics, exendin-3 and exendin-4, from the Mexican Beaded Lizard (Heloderma horridum) and the Gila monster (Heloderma suspectum), respectively, have been characterized at both protein and nucleic acid levels to illustrate the efficacy of the technique and its contribution to biodiversity conservation.
Tianbao Chen - One of the best experts on this subject based on the ideXlab platform.
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Helokinestatin-7 peptides from the venoms of Heloderma Lizards
Peptides, 2012Co-Authors: Hui Wang, Tianbao Chen, Lei Wang, Mei Zhou, Gemma Lowe, Yingqi Zhang, Christopher ShawAbstract:Abstract Helokinestatins 1–6 constitute a family of bradykinin antagonist peptides originally isolated from the venoms of the Gila Monster, Heloderma suspectum and the Mexican Beaded Lizard, Heloderma horridum. Here we report the identification, isolation and preliminary pharmacological characterization of two novel tridecapeptides, named helokinestatin-7S (FDDDSTELILEPR – 1550 Da) and helokinestatin-7H (FDDDSRKLILEPR – 1604 Da), whose primary structures were predicted from cDNAs cloned from venom libraries of respective Heloderma Lizards. Computed molecular masses of putative helokinestatin-7 peptides were used as tools to locate these peptides in archived LC/MS fractions from respective venoms and sequences were confirmed by MS/MS fragmentation. A synthetic replicate of helokinestatin-7H was found to antagonize the relaxation effect of bradykinin on rat arterial smooth muscle but to have no measurable effects alone. In contrast, synthetic helokinestatin-7S was found to directly contract this preparation. Studies on related natural peptides with subtle differences in primary structure can provide the tools for structure/activity studies in pharmacological investigations directed toward unraveling the molecular basis of venom toxicity and for the evaluation of potential therapeutic leads.
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the natriuretic peptide helokinestatin precursor from mexican Beaded Lizard heloderma horridum venom amino acid sequence deduced from cloned cdna and identification of two novel encoded helokinestatins
Peptides, 2011Co-Authors: Mu Yang, Tianbao Chen, Lei Wang, Mei Zhou, Anwei Ding, C. ShawAbstract:Abstract Natriuretic peptides are common components of reptile venoms and molecular cloning of their biosynthetic precursors has revealed that in snakes, they co-encode bradykinin-potentiating peptides and in venomous Lizards, some co-encode bradykinin inhibitory peptides such as the helokinestatins. The common natriuretic peptide/helokinestatin precursor of the Gila Monster, Heloderma suspectum, encodes five helokinestatins of differing primary structures. Here we report the molecular cloning of a natriuretic peptide/helokinestatin precursor cDNA from a venom-derived cDNA library of the Mexican Beaded Lizard (Heloderma horridum). Deduction of the primary structure of the encoded precursor protein from this cloned cDNA template revealed that it consisted of 196 amino acid residues encoding a single natriuretic peptide and five helokinestatins. While the natriuretic peptide was of identical primary structure to its Gila Monster (H. suspectum) homolog, the encoded helokinestatins were not, with this region of the common precursor displaying some significant differences to its H. suspectum homolog. The helokinestatin-encoding region contained a single copy of helokinestatin-1, 2 copies of helokinestatin-3 and single copies of 2 novel peptides, (Phe)5-helokinestatin-2 (VPPAFVPLVPR) and helokinestatin-6 (GPPFNPPPFVDYEPR). All predicted peptides were found in reverse phase HPLC fractions of the same venom. Synthetic replicates of both novel helokinestatins were found to antagonize the relaxing effect of bradykinin on rat tail artery smooth muscle. Thus Lizard venom continues to provide a source of novel biologically active peptides.
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The natriuretic peptide/helokinestatin precursor from Mexican Beaded Lizard (Heloderma horridum) venom: Amino acid sequence deduced from cloned cDNA and identification of two novel encoded helokinestatins☆
Peptides, 2011Co-Authors: Mu Yang, Tianbao Chen, Lei Wang, Mei Zhou, Anwei Ding, Christopher ShawAbstract:Abstract Natriuretic peptides are common components of reptile venoms and molecular cloning of their biosynthetic precursors has revealed that in snakes, they co-encode bradykinin-potentiating peptides and in venomous Lizards, some co-encode bradykinin inhibitory peptides such as the helokinestatins. The common natriuretic peptide/helokinestatin precursor of the Gila Monster, Heloderma suspectum, encodes five helokinestatins of differing primary structures. Here we report the molecular cloning of a natriuretic peptide/helokinestatin precursor cDNA from a venom-derived cDNA library of the Mexican Beaded Lizard (Heloderma horridum). Deduction of the primary structure of the encoded precursor protein from this cloned cDNA template revealed that it consisted of 196 amino acid residues encoding a single natriuretic peptide and five helokinestatins. While the natriuretic peptide was of identical primary structure to its Gila Monster (H. suspectum) homolog, the encoded helokinestatins were not, with this region of the common precursor displaying some significant differences to its H. suspectum homolog. The helokinestatin-encoding region contained a single copy of helokinestatin-1, 2 copies of helokinestatin-3 and single copies of 2 novel peptides, (Phe)5-helokinestatin-2 (VPPAFVPLVPR) and helokinestatin-6 (GPPFNPPPFVDYEPR). All predicted peptides were found in reverse phase HPLC fractions of the same venom. Synthetic replicates of both novel helokinestatins were found to antagonize the relaxing effect of bradykinin on rat tail artery smooth muscle. Thus Lizard venom continues to provide a source of novel biologically active peptides.
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helokinestatin a new bradykinin b2 receptor antagonist decapeptide from Lizard venom
Peptides, 2008Co-Authors: Hang Fai Kwok, Tianbao Chen, Martin Orourke, Craig Ivanyi, David G Hirst, C. ShawAbstract:Abstract Synthetic bradykinin antagonist peptides/peptoids have been powerful tools for delineating the roles of kinins in both normal physiology and in pathological states. Here, we report the identification of a novel, naturally occurring bradykinin B2 receptor antagonist peptide, helokinestatin, isolated and structurally characterized from the venoms of helodermatid Lizards—the Gila monster (Heloderma suspectum) and the Mexican Beaded Lizard (Heloderma horridum). The primary structure of the peptide was established by a combination of microsequencing and mass spectroscopy as Gly-Pro-Pro-Tyr-Gln-Pro-Leu-Val-Pro-Arg (Mr 1122.62). A synthetic replicate of helokinestatin was found to inhibit bradykinin-induced vasorelaxation of phenylephrine pre-constricted rat tail artery smooth muscle, mediated by the B2 receptor sub-type, in a dose-dependent manner. Natural selection, that generates functional optimization of predatory reptile venom peptides, can potentially provide new insights for drug lead design or for normal physiological or pathophysiological processes.
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Isolation and cloning of exendin precursor cDNAs from single samples of venom from the Mexican Beaded Lizard (Heloderma horridum) and the Gila monster (Heloderma suspectum).
Toxicon, 2006Co-Authors: Tianbao Chen, Hang Fai Kwok, Craig Ivanyi, Christopher ShawAbstract:Reptile venoms are complex cocktails of bioactive molecules, including peptides. While the drug discovery potential of most species remains unrealized, many are endangered and afforded protection under international treaties. In this study, we describe how potential clinically important bioactive peptides and their corresponding mRNAs can be structurally characterized from single, small samples of reptile venom. The potential type-2 diabetes therapeutics, exendin-3 and exendin-4, from the Mexican Beaded Lizard (Heloderma horridum) and the Gila monster (Heloderma suspectum), respectively, have been characterized at both protein and nucleic acid levels to illustrate the efficacy of the technique and its contribution to biodiversity conservation.
R. Lane Brown - One of the best experts on this subject based on the ideXlab platform.
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Pseudechetoxin: A peptide blocker of cyclic nucleotide-gated ion channels
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: R. Lane Brown, Karen A West, Tammie L. Haley, John W CrabbAbstract:Ion channels activated by the binding of cyclic nucleotides first were discovered in retinal rods where they generate the cell’s response to light. In other systems, however, it has been difficult to unambiguously determine whether cyclic nucleotide-dependent processes are mediated by protein kinases, their classical effector enzymes, or cyclic nucleotide-gated (CNG) ion channels. Part of this difficulty has been caused by the lack of specific pharmacological tools. Here we report the purification from the venom of the Australian King Brown snake of a peptide toxin that inhibits current through CNG channels. This toxin, which we have named Pseudechetoxin (PsTx), was purified by cation exchange and RP-HPLC and has a molecular mass of about 24 kDa. When applied to the extracellular face of membrane patches containing the α-subunit of the rat olfactory CNG channel, PsTx blocked the cGMP-dependent current with a Ki of 5 nM. Block was independent of voltage and required only a single molecule of toxin. PsTx also blocked CNG channels containing the bovine rod α-subunit with high affinity (100 nM), but it was less effective on the heteromeric version of the rod channel (Ki ≈ 3 μM). We have obtained N-terminal and partial internal sequence data and the amino acid composition of PsTx. These data indicate that PsTx is a basic protein that exhibits some homology with helothermine, a toxin isolated from the venom of the Mexican Beaded Lizard. PsTx promises to be a valuable pharmacological tool for studies on the structure and physiology of CNG channels.
Huei-shien Chiang - One of the best experts on this subject based on the ideXlab platform.
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Effect on human platelet aggregation of phospholipase A2 purified from Heloderma horridum (Beaded Lizard) venom
Biochimica et biophysica acta, 1994Co-Authors: Tur-fu Huang, Huei-shien ChiangAbstract:Abstract By means of gel filtration, ionic exchange chromatography and DEAE-column HPLC, an acidic phospholipase A2 (PLA2) was purified from Beaded Lizard (Heloderma horridum) venom. The purified PLA is a single-chain polypeptide, consisting of about 163 amino acid residues with a molecular mass of 19000 Da as calculated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and amino acid analysis. HHV-PLA showed a rather specific inhibitory effect on platelet aggregation induced by U46619 and epinephrine in human platelet-rich plasma in a dose- and time-dependent manner, whereas it had little effect on collagen- and ADP-induced aggregation. ATP-release reaction induced by various agonists were dose- and time-dependently inhibited by HHV-PLA, even though platelet aggregation was apparently not affected in human washed platelets. When HHV-PLA was chemically modified with p-bromophenacyl bromide, both of its enzymatic acitvity and antiplatelet activity were lost. Furthermore, exogenous lysophosphatidylcholine and HHV-PLA treated phosphatidylcholine inhibited platelet aggregation induced by U46619 in human washed platelets. In conclusion, PLA enzyme from H. horridum venom inhibits exclusively U46619- or thromboxane-induced platelet aggregation of human platelet-rich plasma probably by virtue of their PLA enzymatic acitvity on plasma phospholipids, converting phospholipids (e.g., phosphatidylcholine) into lysophospholipids, which in turn interfere with the coupling of TXA2 receptor and its signalling transduction system.