A Noncompetitive Peptide Inhibitor of the Nicotinic Acetylcholine Receptor from Conus purpurascens Venom † (original) (raw)
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A New Family of Conus Peptides Targeted to the Nicotinic Acetylcholine Receptor
Journal of Biological Chemistry, 1995
In this work, a new family of Conus peptides, the ␣Aconotoxins, which target the nicotinic acetylcholine receptor, is defined. The first members of this family have been characterized from the eastern Pacific species, Conus purpurascens (the purple cone); three peptides that cause paralysis in fish were purified and characterized from milked venom. The sequence and disulfide bonding pattern of one of these, ␣A-conotoxin PIVA, is as follows:
Discovery of a new subclass of α-conotoxins in the venom of Conus australis
Toxicon : official journal of the International Society on Toxinology, 2014
Cone snails (Conus sp.) are poisonous animals that can be found in all oceans where they developed a venomous strategy to prey or to defend. The venom of these species contains an undeniable source of unique and potent pharmacologically active compounds. Their peptide compounds, called conotoxins, are not only interesting for the development of new pharmaceutical ligands, but they are also useful for studying their broad spectrum of targets. One conotoxin family in particular, the α-conotoxins, acts on nicotinic acetylcholine receptors (nAChRs) which dysfunctions play important roles in pathologies such as epilepsy, myasthenic syndromes, schizophrenia, Parkinson's disease and Alzheimer's disease. Here we define a new subclass of the α-conotoxin family. We purified the venom of a yet unexplored cone snail species, i.e. Conus australis, and we isolated a 16-amino acid peptide named α-conotoxin AusIA. The peptide has the typical α-conotoxin CC-Xm-C-Xn-C framework, but both loop...
Biochemistry
We report the purification and characterization of a new conotoxin from the venom of Conus radiatus. The peptide, RS-conotoxin RVIIIA (RS-RVIIIA), is biochemically unique with respect to its amino acid sequence, post-translational modification, and molecular targets. In comparison to other nicotinic antagonists from Conus venoms, RS-RVIIIA exhibits an unusually broad targeting specificity for nicotinic acetylcholine receptor (nAChR) subtypes, as assayed by electrophysiology. The toxin is paralytic to mice and fish, consistent with its nearly irreversible block of the neuromuscular nAChR. Similar to other antagonists of certain neuronal nAChRs, the toxin also elicits seizures in mice upon intracranial injection. The only previously characterized conotoxin from the S superfamily, σ-conotoxin GVIIIA, is a specific competitive antagonist of the 5-HT 3 receptor; thus, RS-RVIIIA defines a novel family of nicotinic antagonists within the S superfamily. All previously characterized competitive conotoxin nAChR antagonists have been members of the A superfamily of conotoxins. Our working hypothesis is that the particular group of fish-hunting Conus species that includes Conus radiatus uses the RS-conotoxin family to target the muscle nAChR and paralyze prey.
International Journal of Peptides, 2013
Conus venoms are rich sources of biologically active peptides that act specifically on ionic channels and metabotropic receptors present at the neuromuscular junction, efficiently paralyzing the prey. Each species of Conus may have 50 to 200 uncharacterized bioactive peptides with pharmacological interest. Conus regius is a vermivorous species that inhabits Northeastern Brazilian tropical waters. In this work, we characterized one peptide with activity on neuronal acetylcholine receptor (nAChR). Crude venom was purified by reverse-phase HPLC and selected fractions were screened and sequenced by mass spectrometry, MALDI-ToF, and ESI-Q-ToF, respectively. A new peptide was identified, bearing two disulfide bridges. The novel 2,701 Da peptide belongs to the cysteine framework I, corresponding to the cysteine pattern CC-C-C. The biological activity of the purified peptide was tested by intracranial injection in mice, and it was observed that high concentrations induced hyperactivity in the animals, whereas lower doses caused breathing difficulty. The activity of this peptide was assayed in patch-clamp experiments, on nAChR-rich cells, in whole-cell configuration. The peptide blocked slow rise-time neuronal receptors, probably 3 4 and/or 3 4 5 subtype. According to the nomenclature, the new peptide was designated as -RgIB.
Journal of Biological Chemistry, 1998
We have isolated and characterized ␣-conotoxin EpI, a novel sulfated peptide from the venom of the molluscivorous snail, Conus episcopatus. The peptide was classified as an ␣-conotoxin based on sequence, disulfide connectivity, and pharmacological target. EpI has homology to sequences of previously described ␣-conotoxins, particularly PnIA, PnIB, and ImI. However, EpI differs from previously reported conotoxins in that it has a sulfotyrosine residue, identified by amino acid analysis and mass spectrometry. Native EpI was shown to coelute with synthetic EpI. The peptide sequence is consistent with most, but not all, recognized criteria for predicting tyrosine sulfation sites in proteins and peptides.
Journal of Biological Chemistry, 1998
We have isolated and characterized ␣-conotoxin EpI, a novel sulfated peptide from the venom of the molluscivorous snail, Conus episcopatus. The peptide was classified as an ␣-conotoxin based on sequence, disulfide connectivity, and pharmacological target. EpI has homology to sequences of previously described ␣-conotoxins, particularly PnIA, PnIB, and ImI. However, EpI differs from previously reported conotoxins in that it has a sulfotyrosine residue, identified by amino acid analysis and mass spectrometry. Native EpI was shown to coelute with synthetic EpI. The peptide sequence is consistent with most, but not all, recognized criteria for predicting tyrosine sulfation sites in proteins and peptides. The activities of synthetic EpI and its unsulfated analogue [Tyr 15 ]EpI were similar. Both peptides caused competitive inhibition of nicotine action on bovine adrenal chromaffin cells (neuronal nicotinic ACh receptors) but had no effect on the rat phrenic nerve-diaphragm (muscle nicotinic ACh receptors). Both EpI and [Tyr 15 ]EpI partly inhibited acetylcholine-evoked currents in isolated parasympathetic neurons of rat intracardiac ganglia. These results indicate that EpI and [Tyr 15 ]EpI selectively inhibit ␣32 and ␣34 nicotinic acetylcholine receptors.
Novel .alpha.- and .omega.-conotoxins and Conus striatus venom
Biochemistry, 1992
Three neurotoxic peptides from the venom of Conus striatus have been purified, biochemically characterized, and chemically synthesized. One of these, an acetylcholine receptor blocker designated a-conotoxin SII, has the sequence GCCCNPACGPNYGCGTSCS. In contrast to all other a-conotoxins, SI1 has three disulfide bonds (instead of two), has no net positive charge, and has a free C-terminus. The other two paralytic peptides are Ca channel-targeted w-conotoxins, SVIA and SVIB. &VIA is the smallest natural w-conotoxin so far characterized and has the sequence CRSSGSPCGVTSICCGRCYRGKCT-NH2. Although w-conotoxin SVIA is a potent paralytic toxic in lower vertebrate species, it was much less effective in mammals. The third toxin, w-conotoxin SVIB, has the sequence CKLKGQSCRKTSYD-CCSGSCGRSGKC-NH2. This peptide has a different pharmacological specificity from other w-conotoxins previously purified from Conus venoms; only o-conotoxin SVIB has proven to be lethal to mice upon ic injection. Binding competition experiments with rat brain synaptosomal membranes indicate that the high-affinity binding site for w-conotoxin SVIB is MVIIA site.
A New α-Conotoxin Which Targets α3β2 Nicotinic Acetylcholine Receptors
Journal of Biological Chemistry, 1996
We have isolated a 16-amino acid peptide from the venom of the marine snail Conus magus which potently blocks nicotinic acetylcholine receptors (nAChRs) composed of ␣32 subunits. This peptide, named ␣-conotoxin MII, was identified by electrophysiologically screening venom fractions against cloned nicotinic receptors expressed in Xenopus oocytes. The peptide's structure, which has been confirmed by mass spectrometry and total chemical synthesis, differs significantly from those of all previously isolated ␣-conotoxins. Disulfide bridging, however, is conserved. The toxin blocks the response to acetylcholine in oocytes expressing ␣32 nAChRs with an IC 50 of 0.5 nM and is 2-4 orders of magnitude less potent on other nAChR subunit combinations. We have recently reported the isolation and characterization of ␣-conotoxin ImI, which selectively targets homomeric ␣7 neuronal nAChRs. Yet other ␣-conotoxins selectively block the muscle subtype of nAChR. Thus, it is increasingly apparent that ␣-conotoxins represent a significant resource for ligands with which to probe structure-function relationships of various nAChR subtypes.