Diversity of Conus neuropeptides.

Conus venoms contain a remarkable diversity of pharmacologically active small peptides. Their targets are ion channels and receptors in the neuromuscular system. The venom of Conus geographus contains high-affinity peptides that act on voltage-sensitive calcium channels, sodium channels, N-methyl-D-aspartate (NMDA) receptors, acetylcholine receptors, and vasopressin receptors; many more peptides with still uncharacterized receptor targets are present in this venom. It now seems that the Conus species (approximately 500 in number) will each use a distinctive assortment of peptides and that the pharmacological diversity in Conus venoms may be ultimately comparable to that of plant alkaloids or secondary metabolites of microorganisms. The cone snails may generate this diverse spectrum of venom peptides by a "fold-lock-cut" synthetic pathway. These peptides are specific enough to discriminate effectively between closely related receptor subtypes and can be used for structure-function correlations.

Lophozozymus pictor toxin: a fluorescent structural isomer of palytoxin.

Purified Lophozozymus pictor toxin (LPTX) shares many properties similar to palytoxin (PTX). LPTX and palytoxin isolated from Palythoa caribaeorum (C-PTX) have similar mol. wts of approx. 2680 on ionspray mass spectrometry (MS). In addition, antibodies against PTX could recognize and bind LPTX. Mixed mode high-performance liquid chromatography (HPLC) of LPTX, C-PTX and H-PTX (isolated from Palythoa tuberculosa) showed a major PTX component common to all three with the characteristic PTX-like UV spectrum at a retention time (Rt) of 17 min. However, LPTX exhibits fluorescence but PTX of equivalent toxicity does not. LPTX showed a unique peak at Rt of approx. 22 min on mixed mode HPLC. In addition, LPTX and C-PTX showed different ion fragmentation patterns on MS/MS. These results suggest that LPTX and the palytoxins are structural isomers, containing at least one difference which gives rise to fluorescence in LPTX.

Conus Peptides: Phylogenetic Range of Biological Activity.

The major function of the venoms of the predatory marine snails belonging to the genus Conus is to paralyze prey. Thus, the venom of each Conus species acts on receptors and ion channels of the prey; previous studies suggested much less activity on homologous receptor targets in more distant taxa. In this article, we address the question of whether some peptide components of Conus venoms ("conopeptides") have "cross-phylum" biological activity. We examined the venom of Conus textile, a mollusk-hunting Conus, using a mammalian biological activity assay. We purified a 23 amino acid "convulsant peptide" with potent activity in the mammalian CNS, even though it comes from the venom of a snail-hunting Conus species. A survey of Conus textile venom fractions indicates that, in addition to the convulsant peptide, many other components of this venom will exhibit "cross-phylum" biological activity. Conopeptides with broad-range phylogenetic specificity should be useful tools for studying the evolution of receptors and ion channels, and of nervous systems.

A molluscivorous Conus toxin: conserved frameworks in conotoxins.

We purified and characterized a 27 amino acid toxin from a snail-hunting Conus venom, Conus textile. This toxin causes convulsive-like activity in snails and causes subordinate lobsters to assume an exaggerated dominant posture. The sequence of this peptide is Trp-Cys-Lys-Gln-Ser-Gly-Glu-Met-Cys-Asn-Leu-Leu-Asp-Gln-Asn-Cys-Cys-Asp- Gly-Tyr-Cys-Ile-Val-Leu-Val-Cys-Thr. The sequence was confirmed by determining the nucleotide sequence of a cDNA clone coding for the peptide. The conservation of Cys residues compared to the omega-conotoxins from piscivorous Conus venom suggests that toxins from different cone venoms may use only a few "Cys-motifs" as conserved structural backbones for targeting to a variety of receptors in different animals.

The spasmodic peptide defines a new conotoxin superfamily.

We purified and characterized a peptide from the venom of Conus textile that makes normal mice assume the phenotype of a well-known mutant, the spasmodic mouse. This "spasmodic" peptide has 27 amino acids, including two gamma-carboxyglutamate (Gla) residues. A cDNA clone encoding the precursor for the peptide was identified; a gamma-carboxylation recognition signal sequence (gamma-CRS) is present in the -1 --> -20 region of the peptide precursor. Both the gamma-CRS and the position of the Gla residues in the mature toxin are notably different from other Gla-containing conopeptides. The spasmodic peptide has a novel disulfide framework and distinct signal sequence which together define a new P-superfamily of conopeptides. A cDNA encoding another member of the P-superfamily was identified from a different species, Conus gloriamaris.