Solution structure of a defensin-like peptide from platypus venom

Three defensin-like peptides (DLPs) were isolated from platypus venom and s equenced. One of these peptides, DLP-1, was synthesized chemically and its three-dimensional structure was determined using NMR spectroscopy. The main structural elements of this 42-residue peptide were an anti-parallel beta- sheet comprising residues 15-18 and 37-40 and a small 3(10) helix spanning residues 10-12. The overall three-dimensional fold is similar to that of be ta-defensin-12, and similar to the sodium-channel neurotoxin ShI (Stichodac tyla helianthus neurotoxin I). However, the side chains known to be functio nally important in beta-defensin-12 and ShI are not conserved in DLP-1, sug gesting that it has a different biological function. Consistent with this c ontention, we showed that DLP-1 possesses no anti-microbial properties and has no observable activity on rat dorsal-root-ganglion sodium-channel curre nts.