Journal Article

Ring closure activates yeast gammaTuRC for species-specific microtubule nucleation

Agard, David A, Zelter, Alex, Kilmartin, John, Greenberg, Charles H, Kollman, Justin M, Fong, Kimberly K, Moritz, Michelle, Fernandez, Jose-jesus, Li, Sam, Davis, Trisha N, Sali, Andrej

2015

Overview

The γ-tubulin ring complex (γTuRC) is the primary microtubule nucleator in cells. γγTuRC is assembled from repeating γγ-tubulin small complex (γTuSC) subunits and is thought to function as a template by presenting a γ-tubulin ring that mimics microtubule geometry. However, a previous yeast γTuRC structure showed γTuSC in an open conformation that prevents matching to microtubule symmetry. By contrast, we show here that γ-tubulin complexes are in a closed conformation when attached to microtubules. To confirm the functional importance of the closed γTuSC ring, we trapped the closed state and determined its structure, showing that the γ-tubulin ring precisely matches microtubule symmetry and providing detailed insight into γTuRC architecture. Importantly, the closed state is a stronger nucleator, thus suggesting that this conformational switch may allosterically control γTuRC activity. Finally, we demonstrate that γTuRCs have a strong preference for tubulin from the same species.

• Publisher: Nature Publishing Group
• Subject: Yeasts