tubulinGTP

TubulinGTP refers to the form of tubulin that is bound to guanosine triphosphate (GTP). In tubulin, a dimer of alpha- and beta-tubulin, GTP binds to both subunits, but the functional consequences differ between the two. The GTP bound to alpha-tubulin is non-exchangeable and is not readily hydrolyzed, whereas the GTP bound to beta-tubulin is exchangeable and is hydrolyzed to GDP after the dimer is incorporated into a microtubule lattice.

In cellular microtubules, GTP-tubulin dimers add predominantly to the growing plus end. Once incorporated, the GTP bound to beta-tubulin is hydrolyzed to GDP, producing a GDP-tubulin lattice. This hydrolysis destabilizes the lattice over time, contributing to the dynamic instability that governs microtubule growth and shrinkage. A region of GTP-bound β-tubulin at the end of a growing microtubule, called the GTP cap, helps stabilize the structure; loss of this cap can trigger rapid depolymerization, or catastrophe.

The balance between GTP-tubulin availability, GTP hydrolysis, and the actions of microtubule-associated proteins (MAPs) and motor proteins determines the dynamics of the cytoskeleton. Experimental tools and analogs, such as non-hydrolyzable GTP analogs, are used to study these processes and to stabilize microtubules in vitro. TubulinGTP is thus central to understanding polymerization dynamics, lattice stability, and the regulation of microtubule behavior in cells.