Microtubule nucleation visualized at high resolution

Microtubules are tube-shaped filaments that serve in cells as tracks for molecular motors and are essential for segregating the genetic material during cell divsion. In human cells, the growth of microtubules starts in a highly regulated manner from a large protein complex called the γ-tubulin ring complex (γTuRC). Using cryo-electron microscopy, we have visualized for the first time at high resolution how this complex "nucleates" the growth of a microtubule. Our work revealed that the complex undergoes a large structural change as the microtubule begins assembling, a change that ensures that γTuRC can enforce the correct tube-like structure of the microtubule. This large-scale structural change of γTuRC is likely the target of regulation in cells. This work provides new insight into the poorly understood molecular mechanism of the control of microtubule polymerization and its regulation in cells and opens up new possibilities to target incorrect microtubule mass regulation in disease.