研究人员确定了与新生微管结合的人类γ-微管环复合体（γTuRC）的冷冻电镜结构。该复合物的结构变化形成了一个闭合构象，确保了γTuRC为人类细胞中存在的13条原丝微管提供模板。闭合是由一个闩锁介导的，该闩锁与结合的微管相互作用，使其成为闭合机制的一部分。进一步的重新排列涉及所有γ-微管环复合体亚基和含肌动蛋白腔桥的移除。
研究人员提出的人类γ-TuRC微管成核机制依赖于大规模的结构变化，而这种变化很可能是细胞中的调控目标。
据悉，微管对细胞内组织和染色体分离至关重要。微管由γTuRC成核。然而，分离的脊椎动物γ-TuRC采用的是开放构象，偏离了微管结构，这就提出了成核机制的问题。
附：英文原文
Title: Transition of human γ-tubulin ring complex into a closed conformation during microtubule nucleation
Author: Cláudia Brito, Marina Serna, Pablo Guerra, Oscar Llorca, Thomas Surrey
Issue&Volume: 2024-02-02
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.
DOI: adk6160
Source: https://www.science.org/doi/10.1126/science.adk6160