Total chemical synthesis and oxidative folding of δ‐conotoxin PVIA containing an N‐terminal propeptide

AbstractSmall disulfide‐rich peptides are translated as larger precursors typically containing an N‐terminal prepro sequence. In this study, we investigated the role of a propeptide in the oxidative folding of an extremely hydrophobic δ‐conotoxin, PVIA. δ‐Conotoxin PVIA (δ‐PVIA) is a 29‐amino acid neurotoxin stabilized by three disulfide bridges. Previous folding studies on δ‐conotoxins revealed that their poor folding properties resulted from their hydrophobicity. However, low folding yields of δ‐PVIA could be improved by the presence of a nonionic detergent, which acted as a chemical chaperone. δ‐PVIA provided an attractive model to investigate whether the hydrophilic propeptide region could function as an intramolecular chaperone. A 58‐amino acid precursor for δ‐PVIA (pro‐PVIA), containing the N‐terminal propeptide covalently attached to the mature conotoxin, was synthesized using native chemical ligation. Oxidative folding of pro‐PVIA resulted in a very low accumulation of the correctly folded form, comparable to that for the mature conotoxin δ‐PVIA. Our results are in accord with the relevant data previously observed for α‐ and ω‐conotoxins, indicating that conotoxin prepro sequences are so‐called class II propeptides, which are not directly involved in the oxidative folding. We hypothesize that these propeptide regions may be important for interactions with protein folding catalysts and sorting receptors during the secretory process. © 2005 Wiley Periodicals, Inc. Biopolymers (Pept Sci), 2005