Contryphan Genes and Mature Peptides in the Venom of Nine Cone Snail Species by Transcriptomic and Mass Spectrometric Analysis.

The occurrence of contryphans, a class of single-disulfide-bond-containing peptides, is demonstrated by the analysis of the venom of nine species of cone snails. Ten full gene sequences and two partial gene sequences coding for contryphan precursor proteins have been identified by next-generation sequencing and compared with available sequences. The occurrence of mature peptides in isolated venom has been demonstrated by LC-ESI-MS/MS analysis. De novo sequencing of reduced, alkylated contryphans from C. frigidus and C. araneosus provides evidence of sequence variation and post-translational modification, notably gamma carboxylation of glutamic acid. The characterization of Fr965 (C. frigidus) provides a rare example of a sequence lacking Pro at position 5 in the disulfide loop. The widespread occurrence of contryphan genes and mature peptides in the venom of diverse cone snails is suggestive of their potential biological significance.