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PUBLISHED ONLINE: 28 OCTOBER 2012 | http://www.nature.com/doifinder/10.1038/nchem.1487
Web End =DOI: 10.1038/NCHEM.1487
Twin disuldes for orthogonal disulde pairing and the directed folding of multicyclic peptides
Chuanliu Wu, Jean-Christophe Leroux* and Marc A. Gauthier*
Multicyclic peptides are emerging as an exciting platform for drug and targeted ligand discovery owing to their expected greater target afnity/selectivity/stability versus linear or monocyclic peptides. However, although the precise pairing of cysteine residues in proteins is routinely achieved in nature, the rational pairing of cysteine residues within polypeptides is a long-standing challenge for the preparation of multicyclic species containing several disulde bridges. Here, we present an efcient and straightforward approach for directing the intermolecular and intramolecular pairing of cysteine residues within peptides using a minimal CXC motif. Orthogonal disulde pairing can be exploited in complex redox media to rationally produce dimeric peptides and bi/tricyclic peptides from fully reduced peptides containing 16 cysteine residues. This strategy, which does not rely on extensive manipulation of the primary sequence, post-translational modication or protecting groups, should greatly benet the development of multicyclic peptide therapeutics and targeting ligands.
Constraining the conformation of peptides through cyclization is a powerful approach for increasing their potency, selectivity and stability as drugs and targeting ligands15. Although this
is often accomplished in the laboratory by cyclic condensation using post-translational reactions2, disulde bridging is the most common way to reduce the conformational space of peptides and proteins in nature6,7. The precise pairing of cysteine residues plays a key role in maintaining the structural and functional integrity of many proteins7,8. This process is often driven by the primary sequence, which can favour one (or few) specic combinations of disulde bonds by prepositioning specic cysteine residues close to each other before disulde formation. However, rationally directing disulde pairing within shorter polypeptides containing multiple cysteine residueswithout extensive sequence manipulation, recourse to elaborate post-translational reactions, or protecting groupsis a long-standing obstacle to the preparation of biosynthetic multicyclic libraries for in vitro/in vivo selection techniques.For example, Heinis et al.9 have recently reported the rst screening of bicyclic peptides as inhibitors for human plasma kallikrein by phage display. The authors expressed a library of peptides containing three cysteine residues, which they cyclize to bicyclic species by post-translational alkylation with tribenzyl bromide. Despite the very innovative aspect of this...