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Publication Abstract from PubMed

The gamma-tubulin ring complex (gamma-TuRC) is a structural template for de novo microtubule assembly from alpha/beta-tubulin units. The isolated vertebrate gamma-TuRC assumes an asymmetric, open structure deviating from microtubule geometry, suggesting that gamma-TuRC closure may underlie regulation of microtubule nucleation. Here, we isolate native gamma-TuRC-capped microtubules from Xenopus laevis egg extract nucleated through the RanGTP-induced pathway for spindle assembly and determine their cryo-EM structure. Intriguingly, the microtubule minus end-bound gamma-TuRC is only partially closed and consequently, the emanating microtubule is locally misaligned with the gamma-TuRC and asymmetric. In the partially closed conformation of the gamma-TuRC, the actin-containing lumenal bridge is locally destabilised, suggesting lumenal bridge modulation in microtubule nucleation. The microtubule-binding protein CAMSAP2 specifically binds the minus end of gamma-TuRC-capped microtubules, indicating that the asymmetric minus end structure may underlie recruitment of microtubule-modulating factors for gamma-TuRC release. Collectively, we reveal a surprisingly asymmetric microtubule minus end protofilament organisation diverging from the regular microtubule structure, with direct implications for the kinetics and regulation of nucleation and subsequent modulation of microtubules during spindle assembly.

gamma-TuRC asymmetry induces local protofilament mismatch at the RanGTP-stimulated microtubule minus end.,Vermeulen BJ, Bohler A, Gao Q, Neuner A, Zupa E, Chu Z, Wurtz M, Jakle U, Gruss OJ, Pfeffer S, Schiebel E EMBO J. 2024 May;43(10):2062-2085. doi: 10.1038/s44318-024-00087-4. Epub 2024 Apr , 10. PMID:38600243^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.