# Consequences of Peptide Macrocyclization Revealed by Virus-Inspired β‑Hairpin Mimetics

## TL;DR

This paper explores how creating macrocyclic peptides that mimic β-hairpin structures can improve their binding to proteins like STAT1, potentially leading to better drug design.

## Contribution

The study introduces a general strategy for β-hairpin macrocyclization to enhance target engagement and provides a kinetic model for improved binding.

## Key findings

- Orthogonal cyclizations improve peptide binding thermodynamics and slow dissociation from the target.
- Interstrand and head-to-tail cross-linking alters peptide structure and dynamics, enhancing target residence.
- Macrocyclic peptides inhibit STAT1 binding to its interferon receptor docking site, showing pharmacological potential.

## Abstract

Mimicry of protein secondary structure elements, such
as α-helices
and β-sheets, using conformationally constrained peptide macrocycles,
can be utilized to disrupt native protein–protein and protein-nucleic
acid interactions. Although α-helical stapled peptides have
been extensively studied as pharmacological probes, the application
of β-sheet and β-hairpin mimetics remains comparatively
limited. Less is known about the structural and biophysical consequences
of β-hairpin macrocyclization in the context of target binding.
In this work, we use a poxvirus immune antagonist protein 018 as a
template for the structure-based design of β-hairpin mimetic
macrocyclic peptides targeting the STAT1 transcription factor. We
demonstrate that successive orthogonal cyclizations have additive
effects on the thermodynamic and kinetic properties of peptide binding,
most notably slowing the dissociation from the target. We elucidate
the structural and dynamic consequences of interstrand and head-to-tail
cross-linking and propose a kinetic model explaining the gains in
target residence. Finally, we highlight the pharmacological potential
of these peptides by competitive inhibition of STAT1 binding to its
cognate interferon receptor docking site. These data suggest that
β-hairpin macrocyclization may represent a general strategy
to extend target engagement, with implications for peptidic probe
design.