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Related Experiment Videos

The minimum GTP cap required to stabilize microtubules

D N Drechsel1, M W Kirschner

  • 1Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448, USA.

Current Biology : CB
|December 1, 1994
PubMed
Summary

A minimum of 40 tubulin subunits forming a GTP cap are needed to stabilize microtubules. This finding supports a model where even one exposed tubulin-GDP subunit can initiate microtubule depolymerization.

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Area of Science:

  • Cell biology
  • Biochemistry
  • Structural biology

Background:

  • Microtubules exhibit dynamic instability, with coexisting growing and shrinking phases.
  • Tubulin subunit GTP hydrolysis is crucial for microtubule dynamics, not assembly.
  • The 'GTP cap' model suggests its loss triggers depolymerization, but direct evidence was lacking.

Purpose of the Study:

  • To determine the minimum GTP cap size required for microtubule stabilization.
  • To investigate the role of GTP hydrolysis in microtubule dynamics.

Main Methods:

  • Developed a novel assay to measure microtubule stabilization.
  • Utilized a slowly hydrolyzed GTP analog (GMPCPP) to form stable caps.
  • Employed rhodamine labeling to quantify cap size.

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Main Results:

  • As few as 40 GMPCPP-tubulin subunits were sufficient to stabilize microtubules against dilution.
  • The assay allowed for direct measurement of the minimum stabilizing cap size.

Conclusions:

  • A cap of approximately 40 subunits, or even a single GTP-bound tubulin subunit per protofilament, stabilizes microtubules.
  • Microtubule depolymerization may initiate with the exposure of a single tubulin-GDP subunit.
  • Findings provide insights into microtubule structure and regulatory mechanisms.