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Published on: March 16, 2014
Structural changes accompanying GTP hydrolysis in microtubules: information from a slowly hydrolyzable analogue
A A Hyman1, D Chrétien, I Arnal
1Cell Biology Program, European Molecular Biology Laboratory, Heidelberg, Germany.
Abstract:
We have used cryoelectron microscopy to try to understand the structural basis for the role of GTP hydrolysis in destabilizing the microtubule lattice. We have measured a structural difference introduced into microtubules by replacing GTP with guanylyl-(alpha,beta)-methylene-diphosphonate (GMPCPP). In a stable GMPCPP microtubule lattice, the moiré patterns change and the tubulin subunits increase in size by 1.5 A. This information provides a clue to the role of hydrolysis in inducing the structural change at the end of a microtubule during the transition from a growing to a shrinking phase.
Insights
GTP hydrolysis destabilizes microtubule structure. Replacing GTP with GMPCPP in microtubules revealed structural changes, showing tubulin subunits increase by 1.5 A, offering clues to microtubule growth and shrinkage transitions.
Area of Science:
- Biochemistry
- Structural Biology
- Cell Biology
Background:
- Microtubules are dynamic polymers essential for cell division and intracellular transport.
- GTP hydrolysis by tubulin is a key factor regulating microtubule dynamics, but its precise structural role remains unclear.
- Understanding microtubule lattice destabilization is crucial for comprehending cell cycle progression and drug development.
Purpose of the Study:
- To elucidate the structural basis of GTP hydrolysis in microtubule lattice destabilization.
- To investigate the structural consequences of inhibiting GTP hydrolysis on the microtubule lattice.
- To provide insights into the transition of microtubules from growing to shrinking phases.
Main Methods:
- Cryoelectron microscopy (cryo-EM) was employed to visualize microtubule structures.
- Microtubules were stabilized using guanylyl-(alpha,beta)-methylene-diphosphonate (GMPCPP) to mimic the GTP-bound state.
- Structural analysis focused on changes in moiré patterns and tubulin subunit dimensions.
Main Results:
- A stable microtubule lattice was formed using GMPCPP, preventing GTP hydrolysis.
- Significant alterations in moiré patterns were observed in GMPCPP-stabilized microtubules compared to GTP-bound microtubules.
- Tubulin subunits within the GMPCPP microtubule lattice showed an average increase in size of 1.5 Å.
Conclusions:
- The structural changes observed with GMPCPP suggest a distinct conformation of the microtubule lattice when GTP hydrolysis is inhibited.
- The 1.5 Å increase in tubulin subunit size provides a quantifiable structural difference linked to the absence of hydrolysis.
- These findings offer critical clues into how GTP hydrolysis induces structural changes at microtubule ends, driving the transition from polymerization to depolymerization.
