Chemical Synthesis and Characterization of an Equinatoxin II(1–85) Analogue

• Main Authors: John A. Karas, Marc-Antoine Sani, Frances Separovic
• Format: Article
• Language: English
• Published: MDPI AG 2017-03-01
• Series: Molecules
• Subjects: native chemical ligation; solid-phase peptide synthesis; selectively labelled proteins; membrane protein structure; solid-state NMR
• Online Access: http://www.mdpi.com/1420-3049/22/4/559
• ISSN: 1420-3049

The chemical synthesis of an 85 residue analogue of the pore-forming protein, Equinatoxin II (EqtII), was achieved. Peptide precursors with over 40 residues were assembled by solid phase synthesis. The EqtII(1–46) fragment was modified to the reactive C-terminal thioester and native chemical ligation was performed with the A47C mutated EqtII(47–85) peptide to form the EqtII(1–85) analogue. Circular dichroism spectroscopy indicated that the N-terminal domain of EqtII(1–46) and EqtII(1–85) maintains predominantly an α-helical structure in solution and also in the presence of lipid micelles. This demonstrates the feasibility of assembling the full 179 residue protein EqtII via chemical means. Site-specific isotopic labels could be incorporated for structural studies in membranes by solid-state NMR spectroscopy.