Transition of human γ-tubulin ring complex into a closed conformation during microtubule nucleation

Brito, Cláudia; Serna, Marina; Guerra, Pablo; Llorca, Óscar; Surrey, Thomas

doi:http://dx.doi.org/10.1126/science.adk6160

Transition of human γ-tubulin ring complex into a closed conformation during microtubule nucleation

Citation

Brito C, Serna M, Guerra P, Llorca O, Surrey T. Transition of human γ-tubulin ring complex into a closed conformation during microtubule nucleation. Science. 2024 Feb 23;383(6685):870-6. DOI: 10.1126/science.adk6160

Abstract

Microtubules are essential for intracellular organization and chromosome segregation. They are nucleated by the γ-tubulin ring complex (γTuRC). However, isolated vertebrate γTuRC adopts an open conformation that deviates from the microtubule structure, raising the question of the nucleation mechanism. Here we determine cryo-electron microscopy structures of human γTuRC bound to a nascent microtubule. Structural changes of the complex into a closed conformation ensure that γTuRC templates the 13-protofilament microtubules that exist in human cells. Closure is mediated by a latch that interacts with incorporating tubulin, making it part of the closing mechanism. Further rearrangements involve all γ-tubulin ring complex subunits and the removal of the actin-containing luminal bridge. Our proposed mechanism of microtubule nucleation by human γTuRC relies on large-scale structural changes that are likely the target of regulation in cells.