Rare-event trajectory ensemble analysis reveals metastable dynamical phases in lattice proteins

TL;DR

This study uses trajectory sampling to reveal non-equilibrium dynamical phase transitions in lattice protein models, showing how sequence heterogeneity influences the nature of these transitions between active and inactive phases.

Contribution

It demonstrates the existence of dynamical phase transitions in lattice proteins and elucidates how sequence heterogeneity affects these transitions compared to homogeneous models.

Findings

Dynamical phase transitions exist between active and inactive phases.

Sequence heterogeneity influences the nature of the dynamical transition.

Transitions occur even in optimized protein sequences.

Abstract

We explore the dynamical large-deviations of a lattice heteropolymer model of a protein by means of path sampling of trajectories. We uncover the existence of non-equilibrium dynamical phase-transitions in ensembles of trajectories between active and inactive dynamical phases, whose nature depends on properties of the interaction potential. When the full heterogeneity of interactions due to the amino-acid sequence is preserved, as in a fully interacting model or in a heterogeneous version of the G\={o} model where only native interactions are considered, the transition is between the equilibrium native state and a highly native but kinetically trapped state. In contrast, for the homogeneous G\={o} model, where there is a single native energy and the sequence plays no role, the dynamical transition is a direct consequence of the static bi-stability between unfolded and native states. In the heterogeneous case the native-active and native-inactive states, despite their static similarity, have widely varying dynamical properties, and the transition between them occurs even in lattice proteins whose sequences are designed to make them optimal folders.