(838.8) Cystine-stapled Helical Peptide from Withania somnifera Is Highly Stable and Cell-permeable

Poster Board Number: B92

Fan Tang (School of Biological Sciences, Nanyang Technological University), Shining Loo (School of Biological Sciences, Nanyang Technological University), Antony Kam (School of Biological Sciences, Nanyang Technological University), James Tam (School of Biological Sciences, Nanyang Technological University)

The alpha-helix is a common structure motif found in proteins but rare in peptides, particularly as a single helix.  Peptide stapling is a synthetic strategy to constrain the helical conformation of a short peptide, generally through covalent linkage of their side chains. They are also known to be cell-penetrating and capable of inhibiting intracellular protein-protein interactions.  However, naturally-occurring stapled peptides are rare. Previously, we discovered lybatides which contain a single helix stapled by cystine. Moreover, lybatides form a new family of cysteine-rich peptides with novel disulfide connectivity. Here, we report the identification and characterization of a new member of cystine-stapled helical peptide, wisotide (wS1) from Withania somnifera which is commonly known as Indian ginseng.  Sequencing by mass spectrometry showed that wS1, with eight cysteine, contains 31 amino acids.  Structural determination by NMR showed that wS1 displays the lybatide-like disulfide connectivities to support an α-helix. Similar to lybatides, the highly disulfide-braced wS1 is resistant to degradation by high temperature, low pH, and proteolysis. Importantly, the anionic cystine-stapled wS1 is cell-penetrating. Database mining further revealed that gt;50 lybatide-like sequences are found in plants. Taken together, wisotide wS1 and the cystine-stapled peptides could represent useful leads of peptide biologics to probe intracellular protein-protein interactions.

This research was supported in part by an Academic Research Grant Tier 3 (MOE2016-T3-1-003) from the Singapore Ministry of Education (MOE) and internal funding from Nanyang Technological University, Synzymes and the Natural Products Center (SYNC).