Abstract
Diversity among Conus toxins mirrors the high species diversity in the Indo-Pacific region, and evolution of both is thought to stem from feeding-niche specialization derived from intra-generic competition. This study focuses on Conus californicus, a phylogenetic outlier endemic to the temperate northeast Pacific. Essentially free of congeneric competitors, it preys on a wider variety of organisms than any other cone snail. Using molecular cloning of cDNAs and mass spectrometry, we examined peptides isolated from venom ducts to elucidate the sequences and post-translational modifications of two eight-cysteine toxins (cal12a and cal12b of type 12 framework) that block voltage-gated Na+ channels. Based on homology of leader sequence and mode of action, these toxins are related to the O-superfamily, but differ significantly from other members of that group. Six of the eight cysteine residues constitute the canonical framework of O-members, but two additional cysteine residues in the N-terminal region define an O+2 classification within the O-superfamily. Fifteen putative variants of Cal12.1 toxins have been identified by mRNAs that differ primarily in two short hypervariable regions and have been grouped into three subtypes (Cal12.1.1-3). This unique modular variation has not been described for other Conus toxins and suggests recombination as a diversity-generating mechanism. We propose that these toxin isoforms show specificity for similar molecular targets (Na+ channels) in the many species preyed on by C. californicus and that individualistic utilization of specific toxin isoforms may involve control of gene expression.
Original language | English (US) |
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Pages (from-to) | 147-161 |
Number of pages | 15 |
Journal | Journal of Experimental Biology |
Volume | 214 |
Issue number | 1 |
DOIs | |
State | Published - Jan 2011 |
Keywords
- Conotoxins
- Peptides
- Peptidomics
- Sodium channels
ASJC Scopus subject areas
- Animal Science and Zoology
- Ecology, Evolution, Behavior and Systematics
- Molecular Biology
- Physiology
- Insect Science
- Aquatic Science