Ring closure activates yeast ?TuRC for species-specific microtubule nucleation.

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

SUBMITTER: Kollman JM 

PROVIDER: S-EPMC4318760 | biostudies-literature | 2015 Feb

REPOSITORIES: biostudies-literature