Myosin motors with artificial lever arms

Area of Science:

• Molecular biology
• Biochemistry
• Cellular mechanics

Background:

• The myosin head's light chain binding domain (LCBD) is crucial for coupling ATP hydrolysis to actin movement.
• Truncation or destabilization of the LCBD impairs myosin motor function, but the underlying reasons remain unclear.
• It is unknown if these impairments stem from mechanical changes or alterations in the catalytic domain's kinetics.

Purpose of the Study:

• To investigate whether mechanical changes in the LCBD affect the kinetic properties of the myosin catalytic domain.
• To develop novel, simplified myosin motor constructs for studying chemo-mechanical coupling.

Main Methods:

• Genetically engineered domains were used to replace the native LCBD in myosin.
• Single-chain, single-headed myosin motors were produced in Dictyostelium discoideum.
• Purification and characterization of motor constructs, including actin motility assays.

Main Results:

• Engineered domains of similar rigidity and dimensions to the LCBD resulted in functional molecular motors.
• These novel motors exhibited unchanged kinetic properties compared to native myosin.
• Actin motility rates were comparable or superior to native myosin, reaching 2.5 and 3.3 microm/s.
• High yield purification (up to 12 mg/l) was achieved.

Conclusions:

• The LCBD's mechanical properties, not its specific structure, are critical for myosin motor function.
• Simplified, genetically tractable myosin constructs serve as excellent models for studying chemo-mechanical coupling.
• These findings offer new avenues for understanding myosin motor mechanisms and engineering novel molecular motors.