Conotoxin Φ‐MiXXVIIA from the Superfamily G2 Employs a Novel Cysteine Framework that Mimics Granulin and Displays Anti‐Apoptotic Activity

Abstract

Conotoxins are a large family of disulfide-rich peptides that contain unique cysteine frameworks that target a broad range of ion channels and receptors. We recently discovered the 33-residue conotoxin Φ-MiXXVIIA from Conus miles with a novel cysteine framework comprising three consecutive cysteine residues and four disulfide bonds. Regioselective chemical synthesis helped decipher the disulfide bond connectivity and the structure of Φ-MiXXVIIA was determined by NMR spectroscopy. The 3D structure displays a unique topology containing two β-hairpins that resemble the N-terminal domain of granulin. Similar to granulin, Φ-MiXXVIIA promotes cell proliferation (EC 17.85 μm) while inhibiting apoptosis (EC 2.2 μm). Additional framework XXVII sequences were discovered with homologous signal peptides that define the new conotoxin superfamily G2. The novel structure and biological activity of Φ-MiXXVIIA expands the repertoire of disulfide-rich conotoxins that recognize mammalian receptors.

Cysteines and Disulfide Bonds as Structure-Forming Units: Insights From Different Domains of Life and the Potential for Characterization by NMR

“…Two recent publications presented structural relatedness between conotoxin structures and the granulin module, which was also solved by NMR and typically contains six disulfide bridges (Hrabal et al, 1996). For conotoxin -MiXXVIIA a novel cysteine framework mimicking granulin and displaying anti-apoptotic activity was observed (Jin et al, 2017). Also for the conotoxin N ext H-Vc7.2 with three disulfide bridges the NMR structure determination revealed a granulin-like fold arising from the common inhibitor cystine knot framework (Nielsen et al, 2019).…”

Marine natural products

“…644 The synthesis, 3D structure and antiproliferative effects of conotoxin F-MiXXVIIA (C. miles), a member of the new G2 toxin superfamily have been reported. 645 Fieen-residue C-amidated conorfamide-Sr3 (C. spurius) blocks activity of Shaker subtype voltage-gated potassium channels. 646 Two hormone-like peptides related to bee brain prohormone-4 and invertebrate neuropeptide elevenin were isolated from C. victoriae, 647 and two 17-residue peptides including anti-mollusc active pn4c were puried from the venom of C. pennaceus.…”

Venomics: A Mini-Review

“…In addition to the discovery of cystine knot peptides, transcriptomics approaches have been used for the discovery of cystine-rich peptides with novel disulfide bond architectures. We have recently characterized a conotoxin identified from the transcriptome of Conus miles [ 47 ]. This peptide, Φ-MiXXVIIA, has a novel cysteine framework, and although the connectivity is the identical to a cystine knot peptide, the topology is different.…”