Ultra-stable peptide scaffolds for protein engineering-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. To date, however, the utilisation of this scaffold has been limited by the inability to synthesise members of the most diverse and biologically active subfamily, the bracelet cyclotides. This study describes the synthesis and first direct oxidative folding of a bracelet cyclotide-cycloviolacin O2-and thus provides an efficient method for exploring the most potent cyclic cystine knot peptides. The linear chain of cycloviolacin O2 was assembled by solid-phase Fmoc peptide synthesis and cyclised 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 characterised and was found to include predominating fully oxidised intermediates that slowly converted to the native peptide structure.
Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala University, Biomedical Centre, Box 574, SE-751 23 Uppsala, Sweden.
Teshome
T
Leta Aboye
Richard J
RJ
Clark
David J
DJ
Craik
Ulf
U
Göransson
D002851:Chromatography, High Pressure Liquid; D047169:Cyclotides / Q000138:chemical synthesis* / Q000737:chemistry*; D003553:Cystine / Q000737:chemistry*; D047168:Cystine Knot Motifs; D004220:Disulfides / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D010084:Oxidation-Reduction; D015202:Protein Engineering / Q000379:methods*; D017510:Protein Folding; D013696:Temperature; D013997:Time Factors
D047169:Cyclotides; D004220:Disulfides; D003553:Cystine; C473355:cycloviolacin O2