Folding-Assisted Peptide Disulfide Formation and Dimerization

Disulfide bonds form covalent bondsbetween distal regionsof peptidesand proteins to dramatically impact their folding, stability, andoligomerization. Given the prevalence of disulfide bonds in many naturalproducts, considerable effort has been invested in site-selectivedisulfide bond formation approaches to control the folding of chemicallysynthesized peptides and proteins. Here, we show that the carefulchoice of thiol oxidation conditions can lead to monomeric or dimericspecies from fully deprotected linear bisthiol peptides. Startingfrom a p53-derived peptide, we found that oxidation under aqueous(nondenaturing) conditions produces antiparallel dimers with enhanced & alpha;-helical character, while oxidation under denaturing conditionspromotes formation of a nonhelical intramolecular disulfide species.Examination across peptide variants suggests that intramolecular disulfideformation is robust across diverse peptide sequences, while dimerizationis sensitive to both the & alpha;-helical folding of the linear peptideand aromatic residues at the dimerization interface. All disulfidespecies are more resistant to protease degradation than the linearpeptide but are easily reduced to restore the initial bisthiol peptide.Both disulfide formation approaches are compatible with & alpha;-helix-stabilizingcross-linkers. These results provide an approach for using disulfidebonds to control peptide folding and oligomerization to better understandhow folding influences interactions with diverse molecular targets.