Peptide toxins find use in medicine, biotechnology, and agriculture. They are exploited as pharmaceutical tools, particularly for the investigation of ion channels. Here, we report the synthesis and activity of a novel family of peptide toxins: the cystine-knotted α nemertides. Following the prototypic α-1 and -2 ( and ), six more nemertides were discovered by mining of available nemertean transcriptomes. Here, we describe their synthesis using solid phase peptide chemistry and their oxidative folding by using an improved protocol. Nemertides α-2 to α-7 (-) were produced to characterize their effect on voltage-gated sodium channels ( BgNa1 and mammalian Nas1.1-1.8). In addition, ion channel activities were ... More
Peptide toxins find use in medicine, biotechnology, and agriculture. They are exploited as pharmaceutical tools, particularly for the investigation of ion channels. Here, we report the synthesis and activity of a novel family of peptide toxins: the cystine-knotted α nemertides. Following the prototypic α-1 and -2 ( and ), six more nemertides were discovered by mining of available nemertean transcriptomes. Here, we describe their synthesis using solid phase peptide chemistry and their oxidative folding by using an improved protocol. Nemertides α-2 to α-7 (-) were produced to characterize their effect on voltage-gated sodium channels ( BgNa1 and mammalian Nas1.1-1.8). In addition, ion channel activities were matched to tests using an microwell assay. Although nemertides demonstrate high sequence similarity, they display variability in activity on the tested Nas. The nemertides are all highly toxic to , with EC values in the sub-low micromolar range, and all manifest preference for the insect BgNa1 channel. Structure-activity relationship analysis revealed key residues for Na-subtype selectivity. Combined with low EC values (e.g., Na1.1: 7.9 nM (α-6); Na1.3: 9.4 nM (α-5); Na1.4: 14.6 nM (α-4)) this underscores the potential utility of α-nemertides for rational optimization to improve selectivity.
