# Preferential Solvation by Trifluoroethanol Drives α‐Helical Folding in the Disordered S2 Region of the Escargot Protein

## TL;DR

A disordered region of the Escargot protein can form helices stabilized by TFE, which helps in protein interactions.

## Contribution

The study reveals how TFE preferentially stabilizes α-helices in the disordered S2 region of the Escargot protein.

## Key findings

- TFE nearly doubles the helix population in the S2 peptide at 40% v/v compared to pure water.
- TFE preferentially accumulates on the peptide domain through nonspecific contacts with polar and nonpolar side chains.
- The structural plasticity of the S2 region is critical for modulating the function of the Escargot protein.

## Abstract

The N‐terminal domain of the Drosophila
melanogaster Escargot transcription factor (Esg) is an intrinsically disordered region (IDR) that complements the DNA‐binding activity of its C‐terminal zinc fingers. Within this IDR, the S2 segment (residues 120–152) is predicted to form an α‐helical molecular recognition feature, a transient structural element implicated in protein–protein interactions. We examined the conformational equilibrium of the S2 peptide in water and in helix‐promoting 2,2,2‐trifluoroethanol (TFE)/water solutions using replica exchange with solute tempering 2 (REST2) simulations and circular dichroism measurements. We show that the peptide can display substantial ellipticity, with TFE nearly doubling the helix population at 40% v/v compared to pure water. Minimum‐distance distribution functions and the Kirkwood–Buff theory of solvation show that TFE preferentially accumulates on the peptide domain. This effect primarily arises from nonspecific contacts between TFE and uncharged polar and nonpolar side chains of the peptide. These findings support the view that the S2 region's structural plasticity is critical for modulating the function of Esg and provide further insights into TFE‐induced helix stabilization.

A disordered S2 region of the Escargot protein forms helices which are stabilized by TFE and are correlated with molecular recognition.© 2026 WILEY‐VCH GmbH