Question

Describe the mechanism by which “nucleotide hydrolysis” regulates microtubule dynamics in plant cells.

Answer 1

Microtubules (MTs) are highly conserved polar polymers that are key elements of the eukaryotic cytoskeleton and are essential for various cell functions.

??-tubulin, a heterodimer containing one structural GTP and one hydrolysable and exchangeable GTP, is the building block of MTs and is formed by the sequential action of several molecular chaperones.  

GTP hydrolysis in the MT lattice is mechanistically coupled with MT growth, thus giving MTs a metastable and dynamic nature. MTs adopt several distinct higher-order organizations that function in cell division and cell morphogenesis.

Microtubules are composed of tubulin dimers (? and ?) that exhibit stochastic growth and shortening, termed dynamic instability.

Dynamic instability is regulated by a stabilizing GTP “cap,” found at the exchangeable GTP-binding site of ?-tubulin exposed on the plus end of a microtubule.

The GTP-bound nucleotide is hydrolyzed on incorporation of ?-tubulin into the microtubule lattice. Upon hydrolysis of GTP at the plus end, microtubules become less stable, resulting in the release of energy stored within the microtubule lattice and polymer shortening.