A mutation uncouples the tubulin conformational and GTPase cycles, revealing allosteric control of microtubule dynamics

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Abstract

Microtubule dynamic instability depends on the GTPase activity of the polymerizing αβ-tubulin subunits, which cycle through at least three distinct conformations as they move into and out of microtubules. How this conformational cycle contributes to microtubule growing, shrinking, and switching remains unknown. Here, we report that a buried mutation in αβ-tubulin yields microtubules with dramatically reduced shrinking rate and catastrophe frequency. The mutation causes these effects by suppressing a conformational change that normally occurs in response to GTP hydrolysis in the lattice, without detectably changing the conformation of unpolymerized αβ-tubulin. Thus, the mutation weakens the coupling between the conformational and GTPase cycles of αβ-tubulin. By showing that the mutation predominantly affects post-GTPase conformational and dynamic properties of microtubules, our data reveal that the strength of the allosteric response to GDP in the lattice dictates the frequency of catastrophe and the severity of rapid shrinking.

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Elisabeth A Geyer

Departments of Biophysics and Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States

Competing interests
The authors declare that no competing interests exist.
Alexander Burns

Departments of Biophysics and Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States

Competing interests
The authors declare that no competing interests exist.
Beth A Lalonde

Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States

Competing interests
The authors declare that no competing interests exist.
Xuecheng Ye

Departments of Biophysics and Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States

Competing interests
The authors declare that no competing interests exist.
Felipe-Andres Piedra

Departments of Biophysics and Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States

Competing interests
The authors declare that no competing interests exist.
Tim C Huffaker

Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States

Competing interests
The authors declare that no competing interests exist.
Luke M Rice

Departments of Biophysics and Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States

For correspondence
Luke.Rice@UTSouthwestern.edu

Competing interests
The authors declare that no competing interests exist.

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