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A TOG:αβ-tubulin complex structure reveals conformation-based mechanisms for a microtubule polymerase

Pelin Ayaz1, Xuecheng Ye, Patrick Huddleston

  • 1Department of Biophysics, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390, USA.

Science (New York, N.Y.)
|August 21, 2012
PubMed

Insights

Stu2p proteins regulate microtubule growth by binding tubulin. Their TOG1 domain binds curved tubulin, explaining how they distinguish between growing and non-growing microtubule ends.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Stu2p/XMAP215/Dis1 proteins are conserved regulators of microtubule dynamics.
  • These proteins utilize tumor overexpressed gene (TOG) domains for microtubule polymerization.
  • The mechanism by which these polymerases discriminate between polymerized and unpolymerized tubulin is not fully understood.

Purpose of the Study:

  • To elucidate the structural basis for Stu2p's discrimination between different tubulin conformations.
  • To understand how TOG domains interact with αβ-tubulin to regulate microtubule growth.

Main Methods:

  • X-ray crystallography was used to determine the structure of the TOG1 domain from Stu2p bound to yeast αβ-tubulin.

Main Results:

  • The TOG1 domain binds αβ-tubulin in a conformation that prevents simultaneous binding of another TOG domain.
  • TOG1 preferentially binds a curved conformation of αβ-tubulin, which is not suitable for microtubule incorporation.
  • The interaction involves surfaces of α- and β-tubulin not typically involved in microtubule assembly.

Conclusions:

  • The conformation-selective binding of TOG1 to αβ-tubulin explains how Stu2p differentiates between unpolymerized and polymerized tubulin.
  • This mechanism allows TOG-containing polymerases to specifically recognize and promote the growth of microtubule ends.

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