Actomyosin: law and order in motility

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Crystal structures of smooth muscle and scallop striated muscle myosin are now available.
• Studies on unconventional myosins, like myosin VI, are influencing the understanding of actin-based motility.
• Previous hypotheses on the molecular mechanism of motility have been refined.

Purpose of the Study:

• To explore the molecular mechanisms of actin-myosin interactions.
• To investigate the role of structural transitions in muscle myosin function.
• To understand the backward movement of myosin VI on actin filaments.

Main Methods:

• X-ray crystallography for determining myosin structures.
• Genetic, biochemical, and biophysical techniques to study myosin function.
• Actin-binding assays to analyze motility mechanisms.

Main Results:

• The crystal structures of smooth muscle and scallop striated muscle myosin have been determined.
• Myosin VI exhibits backward movement on actin, challenging existing models.
• Evidence suggests the actin-myosin binding process and a disorder-to-order transition are crucial for motility.

Conclusions:

• Structural and functional studies of myosins are advancing the field of actin-based motility.
• The discovery of myosin VI's backward motion necessitates new models of molecular motors.
• The actin-myosin binding interface and associated conformational changes are key to myosin function.