Single-molecule analysis of dynein processivity and stepping behavior.

Area of Science:

• Molecular Biology
• Cell Biology
• Biophysics

Background:

• Cytoplasmic dynein is a large motor protein responsible for minus-end-directed movement along microtubules.
• The precise mechanism underlying dynein's processive motility remains incompletely understood.

Purpose of the Study:

• To elucidate the structural and mechanistic basis of cytoplasmic dynein's processivity.
• To determine the roles of dynein's motor domains, tail domain, and associated subunits in motility.

Main Methods:

• Utilized Saccharomyces cerevisiae for recombinant dynein production with a chemically controlled dimerization switch.
• Performed structural and single-molecule analyses to observe dynein's movement dynamics.

Main Results:

• Processivity was found to depend on two dynein motor domains, but not the tail domain or associated subunits.
• Dynein typically moves in 8 nm steps, with observed variations including longer, side, and backward steps.
• Individual motor domains display distinct stepping patterns, suggesting an alternating shuffle between rear and forward positions.

Conclusions:

• Cytoplasmic dynein achieves processivity through the coordinated action of its two motor domains.
• Variable step size and direction indicate a substantial diffusional component, distinguishing it from Kinesin-1 and resembling myosin VI motility.