Question

ATP is the most frequently used source of energy in the cell, but some processes, like microtubule polymerization, favor GTP. why might GTP sometimes be a better option in these cases?

Answer 1

Ans .Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells.

Microtubules assemble only in the presence of GTP- bound tubulin heterodimers , but the   - tubulin-bound GTP is rapidly hydrolyzed to GDP after assembly.

The role of GTP in microtubule assembly is to give tubulin a conformation favourable for polymerization, and then to shift equilibrium irreversibly toward polymerization through the hydrolysis of tubulin - bound GTP. The hydrolysis of GTP is necessary for subsequent disassembly of microtubules.

It is apparent that in order for ATP to support assembly , the E-site must contain GTP which then becomes hydrolyzed.Therefore , ATP cannot be interacting with tubulin at this site.