Structure of the native γ-tubulin ring complex capping spindle microtubules

Area of Science:

• Cell Biology
• Structural Biology
• Biochemistry

Background:

• Microtubules (MTs) are essential cytoskeletal polymers crucial for cell structure, division, and development.
• Microtubule nucleation is primarily mediated by the conserved gamma-tubulin ring complex (γTuRC).
• The precise molecular mechanisms governing γTuRC-mediated microtubule nucleation remain incompletely understood.

Purpose of the Study:

• To elucidate the molecular mechanism of microtubule nucleation by the γTuRC.
• To determine the structure of the native γTuRC at the microtubule minus end.

Main Methods:

• Cryo-electron tomography (cryo-ET) was employed to visualize the native γTuRC.
• Analysis focused on enriched budding yeast spindle microtubules.

Main Results:

• The structure revealed the γTuRC forming a closed ring, actively templating 13-protofilament microtubules.
• A novel coiled-coil protein was observed to link α/β-tubulin subunits to the γTuRC.
• This interaction suggests a role for the coiled-coil protein in enhancing γTuRC-mediated nucleation.

Conclusions:

• A detailed molecular model for γTuRC activation and microtubule nucleation in budding yeast is proposed.
• The findings provide structural insights into the templating role of γTuRC.
• The coiled-coil protein is implicated as a key factor in the nucleation process.