Intrastrand Peptide Staples That Promote β-Sheet Folding, Self-Assembly, and Amyloid Seeding
Abha Dangi, Isaac J. Angera, Juan R. Del Valle
Abstract
Side chain stapling of cysteine (Cys) residues offers convenient entry into constrained peptides with enhanced bioactivity and bioavailability. Despite its widespread application in the constraint of α-helical, PPII, and loop conformations, the stabilization of β-sheet folds via intrastrand side chain Cys stapling remains largely unexplored. Here, we demonstrate that i → i +2 stapling with E -butenyl, butynyl, and m -xylyl linkers significantly enhances the folded population of two distinct β-hairpin model peptides. High-resolution NMR structures reveal that these staples support canonical β-sheet backbone torsions and stabilize cross-strand interactions. Leveraging the maintenance of intact backbone hydrogen-bonding edges, we employed i → i +2 side chain macrocyclization in the design of constrained β-arch peptides derived from the tau protein. We show that intrastrand stapling of a nonaggregation-prone segment promotes self-assembly into β-sheet-like filaments. The resulting filaments also seed the aggregation of endogenous tau in a cell-based assay in a macrocycle- and sequence-dependent manner. These findings establish di-Cys i → i +2 stapling as a versatile and synthetically accessible method to stabilize β-sheet structure and modulate the self-assembly of seed-competent amyloidogenic peptides.