Structural insights into the mechanism of GTP initiation of microtubule assembly

  • Nat Commun. 2023 Sep 25;14(1):5980. doi: 10.1038/s41467-023-41615-w.
Ju Zhou  #  1  2  3  4 ,  Anhui Wang  #  5 ,  Yinlong Song  2  6 ,  Nan Liu  1  2  3 ,  Jia Wang  1  2  3 ,  Yan Li  5 ,  Xin Liang  2 ,  Guohui Li  5 ,  Huiying Chu  7 ,  Hong-Wei Wang  8  9  10
Affiliations
  • 1. State Key Laboratory of Membrane Biology, Tsinghua University, Beijing, 100084, China.
  • 2. Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
  • 3. Beijing Frontier Research Center for Biological Structures, Tsinghua University, Beijing, 100084, China.
  • 4. University of California Berkeley, Berkeley, CA, USA.
  • 5. Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, 457 Zhongshan Road, Dalian, 116023, China.
  • 6. Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, Netherlands.
  • 7. Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, 457 Zhongshan Road, Dalian, 116023, China. [email protected].
  • 8. State Key Laboratory of Membrane Biology, Tsinghua University, Beijing, 100084, China. [email protected].
  • 9. Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China. [email protected].
  • 10. Beijing Frontier Research Center for Biological Structures, Tsinghua University, Beijing, 100084, China. [email protected].
  • # Contributed equally.
PMID: 37749104 DOI: 10.1038/s41467-023-41615-w
Abstract

In eukaryotes, the dynamic assembly of microtubules (MT) plays an important role in numerous cellular processes. The underlying mechanism of GTP triggering MT assembly is still unknown. Here, we present cryo-EM structures of tubulin heterodimer at their GTP- and GDP-bound states, intermediate assembly states of GTP-tubulin, and final assembly stages of MT. Both GTP- and GDP-tubulin heterodimers adopt similar curved conformations with subtle flexibility differences. In head-to-tail oligomers of tubulin heterodimers, the inter-dimer interface of GDP-tubulin exhibits greater flexibility, particularly in tangential bending. Cryo-EM of the intermediate assembly states reveals two types of tubulin lateral contacts, "Tube-bond" and "MT-bond". Further, molecular dynamics (MD) simulations show that GTP triggers lateral contact formation in MT assembly in multiple sequential steps, gradually straightening the curved tubulin heterodimers. Therefore, we propose a flexible model of GTP-initiated MT assembly, including the formation of longitudinal and lateral contacts, to explain the nucleation and assembly of MT.