Structural dynamics of myosin 5 during processive motion revealed by interferometric scattering microscopy

Area of Science:

• Molecular biology
• Biophysics
• Cellular mechanics

Background:

• Myosin 5a is a crucial molecular motor protein responsible for intracellular cargo transport along actin filaments.
• Understanding the precise mechanism of myosin 5a's stepping motion is vital for comprehending cellular transport dynamics.

Purpose of the Study:

• To visualize and characterize the stepping mechanism of myosin 5a at unprecedented spatiotemporal resolution.
• To elucidate head-head coordination, lever-arm motion, and the dynamics of translocating heads during individual steps.

Main Methods:

• Utilized interferometric scattering microscopy with nm spatial and ms temporal precision to track individual myosin 5a heads.
• Improved spatial precision to sub-nm regime to observe atomic-level structural transitions.
• Simultaneously tracked both motor heads to analyze their coordinated movement.

Main Results:

• The detached myosin 5a head maintains a loosely fixed position before controlled rebinding during a step.
• Observed an ångstrom-level structural transition in the motor domain linked to the power stroke.
• Demonstrated a symmetrical walking pattern with consecutive steps following identical paths, resembling a compass-like spinning motion.

Conclusions:

• Provided visualization of critical unknown aspects of the myosin 5a stepping mechanism.
• Revealed detailed insights into head-head coordination and the origin of lever-arm motion.
• Characterized the spatiotemporal dynamics of translocating heads during individual steps, advancing our understanding of molecular motor function.