BPS2026 – Simplifying dynamic instability through the lens of a bacterial actin-like protein model

Across all domains of life, cells use dynamic instability of cytoskeletal components to regulate transport and division. Dynamic instability is the process by which a filament switches from a phase of steady growth to rapid depolymerization, or catastrophic shortening. Dynamic instability was discovered over 40 years ago in microtubules, yet due to their complex nature many basic questions surrounding this process remain unanswered. To address this, we study ParM, a simpler bacterial actin-like filament that also undergoes dynamic instability. We developed a theoretical framework alongside stochastic simulations and compared this to single filament TIRF experiments to achieve a complete biophysical description of dynamic instability in ParM. We find that a simple cap model is sufficient to capture experimental results and determine biologically relevant values for model parameters. This model is the first step in understanding dynamic instability across different domains of life in bacteria, archaea, and eukaryotes and opens the door to synthetically creating dynamically unstable filaments.