Novel .alpha.- and .omega.-conotoxins and Conus striatus venom

Abstract

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 alpha-conotoxin SII, has the sequence GCCCNPACGPNYGCGTSCS. In contrast to all other alpha-conotoxins, SII 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 omega-conotoxins, SVIA and SVIB. omega-SVIA is the smallest natural omega-conotoxin so far characterized and has the sequence CRSSGSPCGVTSICCGRCYRGKCT-NH2. Although omega-conotoxin SVIA is a potent paralytic toxic in lower vertebrate species, it was much less effective in mammals. The third toxin, omega-conotoxin SVIB, has the sequence CKLKGQSCRKTSYDCCSGSCGRSGKC-NH2. This peptide has a different pharmacological specificity from other omega-conotoxins previously purified from Conus venoms; only omega-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 omega-conotoxin SVIB is distinct from the high-affinity omega-conotoxin GVIA or MVIIA site.

Intraspecific variation of venom injected by fish-hunting Conussnails

“…These IV samples contained peptides that were previously characterized from the DV of this species, including the calcium-channel blocker ω-SVIA (Ramilo et al, 1992) and nicotinic acetylcholinereceptor blockers α-SI and α-SII (Ramilo et al, 1992;Zafaralla et al, 1988), as confirmed by MALDI-MS. Interestingly, neither s4a nor s4b were observed components of the IV from these snails.…”

“…It is apparent both by the number of peaks that appear in the chromatograms, and the masses labeled, that IV is by no means identical to DV and contains a small subset of DV peptides, primarily less hydrophobic ones. Identifiable DV and IV peptides were fully processed from their propeptides and contained the known post-translational modifications such as carboxy-terminal amidation (s4a, ω-SVIB and α-SI) and proline hydroxylation (s4a and ω-SVIA; Craig et al, 1998;Ramilo et al, 1992;Zafaralla et al, 1988). Peptides s4a and s4b were also modified by O-glycosylation and pyroglutamylation (Craig et al, 1998).…”

“…Identification of well-known conopeptides by such a mass-matching approach has been used in another report . Since ω-SVIA, ω-SVIB (Ramilo et al, 1992), α-SI, α-SII (Ramilo et al, 1992;Zafaralla et al, 1988) and s4a (Craig et al, 1998) are well-characterized C. striatus peptides, an observed mass within 0.5·Da of the predicted value is sufficient to identify the peptides, and based on this criterion, these peptides were identified. We also determined mass matches based on ESI-MS and MALDI-MS data to within 0.5·Da for three putative peptides by using the calculated molecular masses with expected post-translational modifications predicted from published cDNA sequences.…”

Solution structure of ω‐conotoxin MVIIA using 2D NMR spectroscopy

“…co-CmTxa was synthesized on a re-plumbed ABI Model 430A peptide synthesizer, using standard t-BOC chemistry with some modifications [14] in the manner previously described [15,16]. Synthetic preparations were subjected to amino acid analyses [16] and the results were consistent with the expected amino acid composition (data not shown). The authenticity of the synthetic o)-conotoxins were also confirmed by comparison to the purified, native peptides (kindly provided by Dr. B. Olivera) using a variety of chemical and biological methods.…”

α-Conotoxin EpI, a Novel Sulfated Peptide from Conus episcopatusThat Selectively Targets Neuronal Nicotinic Acetylcholine Receptors

“…1 The majority of ␣-conotoxins isolated from fishhunting cone snails, including GI, GIA, and GII from Conus geographus (4), MI from Conus magus (5), and SI and SII from Conus striatus (6,7), show extensive structural homology, a conserved cysteine framework, and target the muscle subtype of the nAChR. The ␣-conotoxins PnIA and PnIB from a molluschunting cone snail, Conus pennaceus (8), and ImI from a wormhunting cone snail, Conus imperialis (9) share a similar cysteine framework to ␣-conotoxins from fish-hunting cones, but have a different sequence pattern and target the neuronal subtypes of the nAChR.…”