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DOI: 10.1055/s-0028-1084795
Synthesis and folding of the circular cystine knotted cyclotide cycloviolacin O2
The cyclic cystine knot motif, as defined by the cyclotide peptide family, is an attractive scaffold for protein engineering [1]. However, to date the utilization of this scaffold has been limited by the inability to synthesize members of the most diverse and biologically active subfamily, the bracelet cyclotides.
Here we describe the synthesis and first direct oxidative folding of a bracelet cyclotide, cycloviolacin O2, and thus provide an efficient method of exploring the most potent cyclic cystine knot peptides [2]. The linear chain of cycloviolacin O2 was assembled using Fmoc solid phase peptide synthesis and cyclized by thioester-mediated native chemical ligation, and the inherent difficulties of folding bracelet cyclotides were successfully overcome in a single step reaction. The folding pathway was characterized and included predominating fully oxidized intermediates that slowly converted to the native peptide structure.
Acknowledgements: This study was supported by the Swedish International Development Cooperation Agency (SIDA), Dept for Research Cooperation (SAREC) and The Royal Swedish Academy of Sciences..
References: 1. Craik, D.J. (2006) Science 311:1563–1564. 2. Leta Aboye, T. et al. (2008) Chembiochem 9:103–13.