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Description
Spider venom encompasses small peptides that can control the gating properties for a wide range of ion channels with high affinity and specificity. These ion channels are responsible for the coordination and control of many bodily functions such as transducing signals into sensory functions, smooth muscle contractions as well as serving as sensors in volume regulation. Hence, these peptides have been the topic of many research efforts in hopes that they can be used as biomedical therapeutics. Several peptides are known to control the gating properties of ion channels by involving the lipid membrane. GsMTx4, isolated from the Chilean Rose tarantula (Grammostola rosea), is known to selectively inhibit mechanosensitive ion channels by partitioning into the cellular membrane. To further understand this membrane access mechanism, our goal is to investigate the interactions between synthetic GsMTx4 and model lipid bilayers composed of 1,2-dimyristoyl-snglycero- 3-phosphocholine (DMPC) using 31P solid-state nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and negative staining transmission electron microscopy (NS-TEM). Our results reveal GsMTx4 perforates through the model lipid vesicles ultimately creating small vesicles and cylindrical micelles. These findings move us forward in our understanding of how these peptides bind and interact with the lipid bilayer. To perform further structural characterization experiments, a method for generating correctly folded peptides in large quantities and reasonable yields is needed. Native peptides from spider venom share a homologous structure known as the inhibitor cystine knot (ICK) that is comprised of multiple disulfide bonds. This structural configuration provides extraordinary stability, but presents many challenges when trying to produce them. If linearized or reduced, non-native intermolecular and intramolecular disulfide shuffling can occur rendering them biologically inactive or requiring extensive screening of folding conditions. Therefore, we explored two methods of obtaining ICK peptides, GsMTx4 and GsAF2, from the Chilean Rose tarantula that exploit in vivo folding conditions including native extraction and recombinant expression using Escherichia coli (E. coli). Both methods offer the potential of producing natively folded peptides for further experiments.
