Mechanistic insights into Z-ring formation and stability: A Langevin dynamics approach to FtsZ self-assembly

TL;DR

This paper presents a theoretical model and molecular dynamics simulations to understand the self-assembly and stability of the bacterial Z-ring formed by FtsZ, revealing various morphological phases and the impact of activity on ring dynamics.

Contribution

It introduces a novel Langevin dynamics approach modeling FtsZ filaments as semiflexible polymers, elucidating mechanisms of Z-ring formation and stability not previously understood.

Findings

Identified multiple morphological phases including rings and helices.

Demonstrated how treadmilling activity influences Z-ring stability.

Revealed a spooling mechanism for ring formation.

Abstract

The tubulin-like protein FtsZ is crucial for cytokinesis in bacteria and many archaea, forming a ring-shaped structure called the Z-ring at the site of cell division. Despite extensive research, the self-assembly of Z-rings is not entirely understood. We propose a theoretical model based on FtsZ's known filament structures, treating them as semiflexible polymers with specific mechanical properties and lateral inter-segment attraction that can stabilize ring formations. Our molecular dynamics simulations reveal various morphological phases, including open helices, chains, rings, and globules, capturing experimental observations in the fission yeast model using FtsZ from different bacterial species or mutants of Escherichia coli. Using our theoretical model, we explore how treadmilling activity affects Z-ring stability and identify a spooling mechanism of ring formation. The active ring produces contractile, shear, and rotational stresses, which intensify as the Z-ring transitions to an open helix at high activity.