The Experts below are selected from a list of 48 Experts worldwide ranked by ideXlab platform
Baldomero M. Olivera - One of the best experts on this subject based on the ideXlab platform.
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biochemical characterization of κm riiij a kv1 2 channel blocker evaluation of cardioprotective effects of κm conotoxins
Journal of Biological Chemistry, 2010Co-Authors: Ping Chen, Andreas Dendorfer, Rocio K Finolurdaneta, Heinrich Terlau, Baldomero M. OliveraAbstract:Conus Snail (Conus) venoms are a valuable source of pharmacologically active compounds; some of the peptide toxin families from the Snail venoms are known to interact with potassium channels. We report the purification, synthesis, and characterization of κM-conotoxin RIIIJ from the venom of a fish-hunting species, Conus radiatus. This conopeptide, like a previously characterized peptide in the same family, κM-RIIIK, inhibits the homotetrameric human Kv1.2 channels. When tested in Xenopus oocytes, κM-RIIIJ has an order of magnitude higher affinity (IC50 = 33 nm) to Kv1.2 than κM-RIIIK (IC50 = 352 nm). Chimeras of RIIIK and RIIIJ tested on the human Kv1.2 channels revealed that Lys-9 from κM-RIIIJ is a determinant of its higher potency against hKv1.2. However, when compared in a model of ischemia/reperfusion, κM-RIIIK (100 μg/kg of body weight), administered just before reperfusion, significantly reduces the infarct size in rat hearts in vivo without influencing hemodynamics, providing a potential compound for cardioprotective therapeutics. In contrast, κM-RIIIJ does not exert any detectable cardioprotective effect. κM-RIIIJ shows more potency for Kv1.2-Kv1.5 and Kv1.2-Kv1.6 heterodimers than κM-RIIIK, whereas the affinity of κM-RIIIK to Kv1.2-Kv1.7 heterodimeric channels is higher (IC50 = 680 nm) than that of κM-RIIIJ (IC50 = 3.15 μm). Thus, the cardioprotection seems to correlate to antagonism to heteromultimeric channels, involving the Kv1.2 α-subunit rather than antagonism to Kv1.2 homotetramers. Furthermore, κM-RIIIK and κM-RIIIJ provide a valuable set of probes for understanding the underlying mechanism of cardioprotection.
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Conus Snail Venom Peptides
Handbook of Biologically Active Peptides, 2006Co-Authors: Baldomero M. OliveraAbstract:ABSTRACT Cone Snails are a large genus (500–700 species) of venomous predators. They comprise only a minor fraction of the total biodiversity of molluscs; the overwhelming majority of peptides from molluscan venoms are uncharacterized. Peptides from Conus venoms are generally small (10–30 amino acids) and disulfide-rich, often with unusual posttranslationally modified amino acids (i.e., γ-carboxyglutamate, 6-bromotryptophan, d -phenylalanine, etc.). Most Conus peptides target ligand-gated or voltage-gated ion channels, or G-protein-coupled receptors. Conotoxins are widely used for basic neuroscience research; a few have reached human clinical trials, and one is an approved drug for intractable pain.
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biochemical and gene expression analyses of conotoxins in Conus textile venom ducts
Biochemical and Biophysical Research Communications, 2005Co-Authors: James E Garrett, Baldomero M. Olivera, Maren Watkins, Olga Buczek, Grzegorz BulajAbstract:Each Conus Snail species produces 50-200 unique peptide-based conotoxins, derived from a number of different gene superfamilies. Conotoxins are synthesized and secreted in a long venom duct, but biochemical and molecular aspects of their biosynthesis remain poorly understood. Here, we analyzed expression patterns of conotoxin genes belonging to different superfamilies in Conus textile venom ducts. The results demonstrate that specific gene families are expressed in particular regions of the venom duct. Biochemical analysis using liquid chromatography and mass spectrometry revealed an even more localized accumulation of individual conotoxins. This study demonstrates for the first time that specialization of gene expression, processing, and secretion of conotoxins occurs in different regions of the venom duct.
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Propeptide does not act as an intramolecular chaperone but facilitates protein disulfide isomerase-assisted folding of a conotoxin precursor
Biochemistry, 2004Co-Authors: Olga Buczek, Baldomero M. Olivera, Grzegorz BulajAbstract:Conotoxins comprise a large and diverse group of peptide neurotoxins derived from Conus Snail venoms; most contain multiple disulfide bonds. The conotoxin precursors consist of three distinct domains: the N-terminal signal sequence, an intervening propeptide region, and the C-terminal mature conotoxin. Formation of the native disulfide bonds during the oxidative folding of conotoxins is a prerequisite for their proper biological function, but in numerous in vitro folding experiments with mature conotoxins, a lack of specificity in formation of the native Cys−Cys connectivities is observed. The mechanisms that ensure that the native disulfide bonds are formed in venom ducts during biosynthesis remain unknown. To evaluate whether the propeptide could potentially function as an intramolecular chaperone, we studied the oxidative folding of a conotoxin precursor, pro-GI, belonging to the α-conotoxin family. Our results indicate that the propeptide sequence did not directly contribute to folding kinetics and t...
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Identification of a vitamin K‐dependent carboxylase in the venom duct of a Conus Snail
FEBS letters, 1997Co-Authors: Thomas B. Stanley, Baldomero M. Olivera, Darrel W. Stafford, Pradip K. BandyopadhyayAbstract:Abstract Peptides from the venom ducts of cone Snails (genus Conus) contain γ-carboxyglutamate residues. The γ-glutamyl carboxylase responsible for this post-translational modification is localized in the microsomal fraction, strictly dependent on vitamin K, activated by ammonium sulfate, and is associated with endogenous substrate. The Km of the enzyme for vitamin K is comparable to that for the bovine carboxylase. However, a propeptide containing substrate related to the blood coagulation protein factor IX, a highly efficient substrate for the bovine enzyme, was poorly carboxylated by the Conus enzyme, suggesting differences in γ-carboxylase recognition signal sequences and/or structural requirements at the carboxylation site.
Pradip K. Bandyopadhyay - One of the best experts on this subject based on the ideXlab platform.
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Identification of a vitamin K‐dependent carboxylase in the venom duct of a Conus Snail
FEBS letters, 1997Co-Authors: Thomas B. Stanley, Baldomero M. Olivera, Darrel W. Stafford, Pradip K. BandyopadhyayAbstract:Abstract Peptides from the venom ducts of cone Snails (genus Conus) contain γ-carboxyglutamate residues. The γ-glutamyl carboxylase responsible for this post-translational modification is localized in the microsomal fraction, strictly dependent on vitamin K, activated by ammonium sulfate, and is associated with endogenous substrate. The Km of the enzyme for vitamin K is comparable to that for the bovine carboxylase. However, a propeptide containing substrate related to the blood coagulation protein factor IX, a highly efficient substrate for the bovine enzyme, was poorly carboxylated by the Conus enzyme, suggesting differences in γ-carboxylase recognition signal sequences and/or structural requirements at the carboxylation site.
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identification of a vitamin k dependent carboxylase in the venom duct of a Conus Snail
FEBS Letters, 1997Co-Authors: Thomas B. Stanley, Baldomero M. Olivera, Darrel W. Stafford, Pradip K. BandyopadhyayAbstract:Abstract Peptides from the venom ducts of cone Snails (genus Conus) contain γ-carboxyglutamate residues. The γ-glutamyl carboxylase responsible for this post-translational modification is localized in the microsomal fraction, strictly dependent on vitamin K, activated by ammonium sulfate, and is associated with endogenous substrate. The Km of the enzyme for vitamin K is comparable to that for the bovine carboxylase. However, a propeptide containing substrate related to the blood coagulation protein factor IX, a highly efficient substrate for the bovine enzyme, was poorly carboxylated by the Conus enzyme, suggesting differences in γ-carboxylase recognition signal sequences and/or structural requirements at the carboxylation site.
Thomas B. Stanley - One of the best experts on this subject based on the ideXlab platform.
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Identification of a vitamin K‐dependent carboxylase in the venom duct of a Conus Snail
FEBS letters, 1997Co-Authors: Thomas B. Stanley, Baldomero M. Olivera, Darrel W. Stafford, Pradip K. BandyopadhyayAbstract:Abstract Peptides from the venom ducts of cone Snails (genus Conus) contain γ-carboxyglutamate residues. The γ-glutamyl carboxylase responsible for this post-translational modification is localized in the microsomal fraction, strictly dependent on vitamin K, activated by ammonium sulfate, and is associated with endogenous substrate. The Km of the enzyme for vitamin K is comparable to that for the bovine carboxylase. However, a propeptide containing substrate related to the blood coagulation protein factor IX, a highly efficient substrate for the bovine enzyme, was poorly carboxylated by the Conus enzyme, suggesting differences in γ-carboxylase recognition signal sequences and/or structural requirements at the carboxylation site.
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identification of a vitamin k dependent carboxylase in the venom duct of a Conus Snail
FEBS Letters, 1997Co-Authors: Thomas B. Stanley, Baldomero M. Olivera, Darrel W. Stafford, Pradip K. BandyopadhyayAbstract:Abstract Peptides from the venom ducts of cone Snails (genus Conus) contain γ-carboxyglutamate residues. The γ-glutamyl carboxylase responsible for this post-translational modification is localized in the microsomal fraction, strictly dependent on vitamin K, activated by ammonium sulfate, and is associated with endogenous substrate. The Km of the enzyme for vitamin K is comparable to that for the bovine carboxylase. However, a propeptide containing substrate related to the blood coagulation protein factor IX, a highly efficient substrate for the bovine enzyme, was poorly carboxylated by the Conus enzyme, suggesting differences in γ-carboxylase recognition signal sequences and/or structural requirements at the carboxylation site.
Grzegorz Bulaj - One of the best experts on this subject based on the ideXlab platform.
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biochemical and gene expression analyses of conotoxins in Conus textile venom ducts
Biochemical and Biophysical Research Communications, 2005Co-Authors: James E Garrett, Baldomero M. Olivera, Maren Watkins, Olga Buczek, Grzegorz BulajAbstract:Each Conus Snail species produces 50-200 unique peptide-based conotoxins, derived from a number of different gene superfamilies. Conotoxins are synthesized and secreted in a long venom duct, but biochemical and molecular aspects of their biosynthesis remain poorly understood. Here, we analyzed expression patterns of conotoxin genes belonging to different superfamilies in Conus textile venom ducts. The results demonstrate that specific gene families are expressed in particular regions of the venom duct. Biochemical analysis using liquid chromatography and mass spectrometry revealed an even more localized accumulation of individual conotoxins. This study demonstrates for the first time that specialization of gene expression, processing, and secretion of conotoxins occurs in different regions of the venom duct.
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Propeptide does not act as an intramolecular chaperone but facilitates protein disulfide isomerase-assisted folding of a conotoxin precursor
Biochemistry, 2004Co-Authors: Olga Buczek, Baldomero M. Olivera, Grzegorz BulajAbstract:Conotoxins comprise a large and diverse group of peptide neurotoxins derived from Conus Snail venoms; most contain multiple disulfide bonds. The conotoxin precursors consist of three distinct domains: the N-terminal signal sequence, an intervening propeptide region, and the C-terminal mature conotoxin. Formation of the native disulfide bonds during the oxidative folding of conotoxins is a prerequisite for their proper biological function, but in numerous in vitro folding experiments with mature conotoxins, a lack of specificity in formation of the native Cys−Cys connectivities is observed. The mechanisms that ensure that the native disulfide bonds are formed in venom ducts during biosynthesis remain unknown. To evaluate whether the propeptide could potentially function as an intramolecular chaperone, we studied the oxidative folding of a conotoxin precursor, pro-GI, belonging to the α-conotoxin family. Our results indicate that the propeptide sequence did not directly contribute to folding kinetics and t...
Darrel W. Stafford - One of the best experts on this subject based on the ideXlab platform.
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Identification of a vitamin K‐dependent carboxylase in the venom duct of a Conus Snail
FEBS letters, 1997Co-Authors: Thomas B. Stanley, Baldomero M. Olivera, Darrel W. Stafford, Pradip K. BandyopadhyayAbstract:Abstract Peptides from the venom ducts of cone Snails (genus Conus) contain γ-carboxyglutamate residues. The γ-glutamyl carboxylase responsible for this post-translational modification is localized in the microsomal fraction, strictly dependent on vitamin K, activated by ammonium sulfate, and is associated with endogenous substrate. The Km of the enzyme for vitamin K is comparable to that for the bovine carboxylase. However, a propeptide containing substrate related to the blood coagulation protein factor IX, a highly efficient substrate for the bovine enzyme, was poorly carboxylated by the Conus enzyme, suggesting differences in γ-carboxylase recognition signal sequences and/or structural requirements at the carboxylation site.
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identification of a vitamin k dependent carboxylase in the venom duct of a Conus Snail
FEBS Letters, 1997Co-Authors: Thomas B. Stanley, Baldomero M. Olivera, Darrel W. Stafford, Pradip K. BandyopadhyayAbstract:Abstract Peptides from the venom ducts of cone Snails (genus Conus) contain γ-carboxyglutamate residues. The γ-glutamyl carboxylase responsible for this post-translational modification is localized in the microsomal fraction, strictly dependent on vitamin K, activated by ammonium sulfate, and is associated with endogenous substrate. The Km of the enzyme for vitamin K is comparable to that for the bovine carboxylase. However, a propeptide containing substrate related to the blood coagulation protein factor IX, a highly efficient substrate for the bovine enzyme, was poorly carboxylated by the Conus enzyme, suggesting differences in γ-carboxylase recognition signal sequences and/or structural requirements at the carboxylation site.