J. McIntosh - Academia.edu (original) (raw)
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Papers by J. McIntosh
Journal of Biological Chemistry, 2006
The molluskan acetylcholine-binding protein (AChBP) is a homolog of the extracellular binding dom... more The molluskan acetylcholine-binding protein (AChBP) is a homolog of the extracellular binding domain of the pentameric ligand-gated ion channel family. AChBP most closely resembles the ␣-subunit of nicotinic acetylcholine receptors and in particular the homomeric ␣7 nicotinic receptor. We report the isolation and characterization of an ␣-conotoxin that has the highest known affinity for the Lymnaea AChBP and also potently blocks the ␣7 nAChR subtype when expressed in Xenopus oocytes. Remarkably, the peptide also has high affinity for the ␣32 nAChR indicating that ␣-conotoxin OmIA in combination with the AChBP may serve as a model system for understanding the binding determinants of ␣32 nAChRs. ␣-Conotoxin OmIA was purified from the venom of Conus omaria. It is a 17amino-acid, two-disulfide bridge peptide. The ligand is the first ␣-conotoxin with higher affinity for the closely related receptor subtypes, ␣32 versus ␣62, and selectively blocks these two subtypes when compared with ␣22, ␣42, and ␣11␦⑀ nAChRs.
The Journal of biological chemistry, Jan 7, 2005
Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated ion channels. Alpha subuni... more Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated ion channels. Alpha subunits, together with beta 2 and/or beta 4 subunits, form ligand-binding sites at alpha/beta subunit interfaces. Predatory marine snails of the genus Conus are a rich source of nAChR-targeted peptides. Using conserved features of the alpha-conotoxin signal sequence and 3'-untranslated sequence region, we have cloned a novel gene from the fish-eating snail, Conus bullatus; the gene codes for a previously unreported alpha-conotoxin with unusual 4/4 spacing of amino acids in the two disulfide loops. Chemical synthesis of the predicted mature toxin was performed. The resulting peptide, alpha-conotoxin BuIA, was tested on cloned nAChRs expressed in Xenopus oocytes. The peptide potently blocks numerous rat nAChR subtypes, with highest potency for alpha 3- and chimeric alpha 6-containing nAChRs; BuIA blocks alpha 6/alpha 3 beta 2 nAChRs with a 40,000-fold lower IC(50) than alpha 4 beta 2 nAChRs...
Journal of Biological Chemistry, 2006
The molluskan acetylcholine-binding protein (AChBP) is a homolog of the extracellular binding dom... more The molluskan acetylcholine-binding protein (AChBP) is a homolog of the extracellular binding domain of the pentameric ligand-gated ion channel family. AChBP most closely resembles the ␣-subunit of nicotinic acetylcholine receptors and in particular the homomeric ␣7 nicotinic receptor. We report the isolation and characterization of an ␣-conotoxin that has the highest known affinity for the Lymnaea AChBP and also potently blocks the ␣7 nAChR subtype when expressed in Xenopus oocytes. Remarkably, the peptide also has high affinity for the ␣32 nAChR indicating that ␣-conotoxin OmIA in combination with the AChBP may serve as a model system for understanding the binding determinants of ␣32 nAChRs. ␣-Conotoxin OmIA was purified from the venom of Conus omaria. It is a 17amino-acid, two-disulfide bridge peptide. The ligand is the first ␣-conotoxin with higher affinity for the closely related receptor subtypes, ␣32 versus ␣62, and selectively blocks these two subtypes when compared with ␣22, ␣42, and ␣11␦⑀ nAChRs.
The Journal of biological chemistry, Jan 7, 2005
Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated ion channels. Alpha subuni... more Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated ion channels. Alpha subunits, together with beta 2 and/or beta 4 subunits, form ligand-binding sites at alpha/beta subunit interfaces. Predatory marine snails of the genus Conus are a rich source of nAChR-targeted peptides. Using conserved features of the alpha-conotoxin signal sequence and 3'-untranslated sequence region, we have cloned a novel gene from the fish-eating snail, Conus bullatus; the gene codes for a previously unreported alpha-conotoxin with unusual 4/4 spacing of amino acids in the two disulfide loops. Chemical synthesis of the predicted mature toxin was performed. The resulting peptide, alpha-conotoxin BuIA, was tested on cloned nAChRs expressed in Xenopus oocytes. The peptide potently blocks numerous rat nAChR subtypes, with highest potency for alpha 3- and chimeric alpha 6-containing nAChRs; BuIA blocks alpha 6/alpha 3 beta 2 nAChRs with a 40,000-fold lower IC(50) than alpha 4 beta 2 nAChRs...