Figure 2

Schematic representation of toxin precursors, overall RACE amplification strategy and identification of toxin superfamilies. (A) Schematic representation of a typical spider peptide precursor showing the signal peptide in orange, the propeptide in purple, and the mature toxin in black. After translation, the signal and propeptide regions are proteolytically removed to yield a functional mature toxin. (B) General overview of the RACE protocol for sequencing hexatoxin transcripts. Adaptors are added to the 5’ and 3’ end of transcripts during cDNA library preparation. In both 3’ and 5’ RACE, gene-specific primers are used in the forward (3’ RACE) or reverse (5’ RACE) orientation to amplify full-length sequences. The resulting PCR products are then cloned and sequenced. (C) Schematic representation of the Shiva superfamily highlighting the combinatorial nature of spider-venom peptides.