Molecular Dynamics Simulations of Cytochrome c un-folding in AOT Reverse Micelles: the first steps

TL;DR

This study uses molecular dynamics simulations to investigate how horse cytochrome c unfolds in AOT reverse micelles, revealing hydration-dependent structural stability and initial unfolding steps.

Contribution

First simulation-based analysis of cytochrome c unfolding in AOT reverse micelles, highlighting hydration effects on protein stability and early denaturation events.

Findings

Protein stability depends on micellar hydration levels.

Unfolding initiates at high water content, affecting loops and heme region.

AOT molecules bind selectively to lysine residues in small micelles.

Abstract

This paper explores the reduced form of horse cytochrome c confined in reverse micelles (RM) of so-dium bis-(2-ethylhexyl) sulfosuccinate (AOT) in isooctane by molecular dynamics simulation. RMs of two sizes were constructed at a water content of Wo = [H2O]/[AOT] = 5.5 and 9.1. Our results show that the protein secondary structure and the heme conformation both depend on micellar hydration. At low hydration, the protein structure and the heme moiety remain stable, whereas at high water content the protein becomes unstable and starts to unfold. At Wo = 9.1, according to the X-ray structure, conforma-tional changes are mainly localized on protein loops and around the heme moiety, where we observe a partial opening of the heme crevice. These findings suggest that within our time window (10 ns), the structural changes observed at the heme level are the first steps of the protein denaturation process, pre-viously described experimentally in micellar solutions. In addition, a specific binding of AOT molecules to a few lysine residues of the protein was found only in the small-sized RM.