Sea anemones are a rich source of peptide toxins known to display a diverse range of biological activities, especially targeting membrane proteins such as ion channels, receptors and transporters. These peptide toxins and their analogues are typically highly stable and selective for their molecular targets. This enables the investigation of their potential as molecular tools, insecticides, and therapeutics [1]. Recent transcriptomic and proteomic analyses of the sea anemone Telmatactis stephensoni identified a novel 38-residue peptide, designated Tst2 [2]. We determined the solution structure of Tst2 based on NMR data [3], revealing that it adopts an inhibitor cystine knot (ICK) structural motif [4]. The biological activity profile of Tst2 was assessed against various ion channels using electrophysiological assays. Tst2 showed > 50% inhibition of the transient receptor potential subfamily V member 1 (TRPV1) at 100 nM [3]. This relatively potent TRPV1 inhibitor may therefore be an interesting lead for the development of novel analgesics and anti-inflammatory drugs. We are currently exploring the structure-activity relationship of Tst2 to identify the key residues for TRPV1 inhibition.