Elucidating chiral myosin-induced actin dynamics: From single-filament behavior to collective structures

Area of Science:

• Cell Biology
• Biophysics
• Molecular Motors

Background:

• The myosin superfamily is diverse, with over 70 classes and subclasses.
• Myosins exhibit varied properties like velocity, ATPase activity, duty ratio, and directionality.
• A newly identified myosin property involves driving actin filaments along chiral curved trajectories.

Purpose of the Study:

• To investigate the unexplored chiral motion of myosins in vitro.
• To characterize the mechanism of chiral actin filament movement driven by myosin XI.
• To explore the collective dynamics and self-organization of actin filaments driven by chiral myosins.

Main Methods:

• In vitro investigation of *Chara corallina* myosin XI (CcXI) activity.
• Analysis of actin filament movement along chiral curved trajectories.
• Observation of collective dynamics and structure formation at elevated actin concentrations.

Main Results:

• CcXI drives fast clockwise (CW) movement of actin filaments via asymmetric tip displacement.
• Myosin density influences the curvature of chiral motion.
• Elevated actin concentrations induce collective dynamics, forming stable, rotating actin chiral rings (ACRs).
• ACRs exhibit persistent CW rotation and remarkable structural stability, even after rotation ceases.

Conclusions:

• Myosins with chiral activity can autonomously organize actin filaments into stable, chiral structures through collective motion.
• This provides insights into actin self-organization by unconventional myosins.
• Motor-driven molecular asymmetry can lead to cellular-scale structural chirality, crucial for cell chirality and asymmetry during development.