Three-dimensional structural dynamics of myosin V by single-molecule fluorescence polarization

Area of Science:

• Molecular Biology
• Biophysics
• Structural Biology

Background:

• Actomyosin motility generates force and motion through myosin's lever arm domain.
• The precise dynamics of myosin lever arm tilting during function remain unclear.

Purpose of the Study:

• To investigate the structural dynamics of the myosin V light chain domain during actin translocation.
• To provide real-time, three-dimensional measurements of myosin V's lever arm motion.

Main Methods:

• Utilized single-molecule fluorescence polarization.
• Measured orientation of individual protein domains with 20-40 ms time resolution.
• Employed fluorescent calmodulin as a probe for myosin light chains.

Main Results:

• Observed myosin V's calmodulin light chains tilting between two distinct angles during processive movement along actin.
• Provided direct evidence for lever arm rotation in the calmodulin-binding domain of myosin V.
• Demonstrated a 'hand-over-hand' mechanism for myosin V translocation.

Conclusions:

• The study supports the lever arm hypothesis for actomyosin motility.
• The findings elucidate the mechanism of myosin V's movement along actin filaments.
• The technique is adaptable for studying real-time structural dynamics in other biological systems.