A bioinformatics survey for conotoxin-like sequences in three turrid snail venom duct transcriptomes

The repertoire of venom peptides produced by Conoidean snails has shown to be useful for therapeutic and neuropharmacologic applications. Despite their dominance in terms of species number, the Family Turridae is the least studied among their other Conoidean counterparts. They provide a vast resource of pharmacological material only hindered by the inaccessibility of their deep water habitat for sample collection and their small size that allows only a limited amount of material from their venom duct amenable for analysis. Using high-throughput transcriptome sequencing, toxin transcripts can be extracted bioinformatically to fast-track toxin discovery. This approach was utilized on the venom duct transcriptomes of three species of turrids: Unedogemmula bisaya, Crassispira cerithina, and Gemmula speciosa and resulted in the discovery of 41, 22, and 74 putative turrid toxin genes, respectively. Comparisons among these turrid toxin genes to conotoxins show (i) similar superfamily precursors between conotoxins and turrid toxins for the classes D, I2, L, M, O1, O2, and P, (ii) a wider range of peptide lengths of up to 190 amino acids long for mature turritoxin, and (iii) nondisulfide-rich turritoxins with the B2 signal sequence. Novel superfamilies and cysteine frameworks including a novel 14-cysteine residue framework were also obtained.