Structural basis for two-way communication between dynein and microtubules

Area of Science:

• Molecular Biology
• Biophysics
• Structural Biology

Background:

• Cytoplasmic dynein is a motor protein essential for intracellular transport.
• Its movement along microtubule tracks depends on communication between the microtubule-binding domain (MTBD) and the ATPase domain via a coiled-coil stalk.
• The precise structural mechanisms underlying this communication are not fully understood.

Purpose of the Study:

• To elucidate the structural basis of communication between the MTBD and ATPase domain of cytoplasmic dynein.
• To investigate how microtubule binding affinity is regulated and how conformational changes propagate within the dynein motor.

Main Methods:

• Utilized nuclear magnetic resonance (NMR) and cryo-electron microscopy (cryo-EM) to analyze dynein structures.
• Introduced a disulfide bond to the stalk region to experimentally control MTBD affinity (high-affinity vs. low-affinity states).

Main Results:

• Structural analysis revealed that altered MTBD affinity in the MT-unbound state is mediated by a half-turn helical slide in the stalk.
• This helical sliding suggests that structural changes are transmitted from the ATPase domain towards the MTBD.
• Microtubule binding was observed to induce further stalk helix sliding, indicating propagation of conformational changes towards the ATPase domain.
• Differences in the MT-binding surface between high- and low-affinity states were identified.

Conclusions:

• Proposed a potential mechanism for the directional bias of dynein movement on microtubules based on observed structural changes.
• Demonstrated that stalk helix sliding is a key mechanism for regulating dynein's microtubule binding affinity and transmitting conformational signals.
• Provided structural insights into the allosteric communication within the cytoplasmic dynein motor complex.