Title: GTP hydrolysis drives microtubule growth in dynamic instability:

Revisiting overlooked observations. Review.

Authors: Etsuko Muto, Shinji Kamimura, Ken Sekimoto

Preprint : https://hal.science/hal-05548311 (published on Mar 11, 2026)

We present a novel perspective for the mechanism of dynamic instability (DI).

・ Our model (upper panel): Microtubule (MT) growth is attained by the formation of lateral

bonds between straight protofilaments, coupled with GTP hydrolysis. When the coupling is failed,

the resulting free GDP-protofilament bends outward, eventually leading to catastrophe.

・ GTP-cap model (lower panel): In contrast, conventional model attributes MT stability to a GTP-

tubulin (Tb) cap and catastrophe to its loss.

Coupling of microtubule polymerization and GTP hydrolysis

(The figure adapted from preprint hal-05548311)

Critical facts we highlight (hitherto overlooked)

Our new model weighs the following facts that have been overlooked.

1. MT growth requires seeds and GTP hydrolysis:

DI is a phenomenon occurring at sub-critical Tb concentration for spontaneous nucleation ([Tb] < Cc2),

where a seed is essential for MT elongation. In this concentration range, MT polymerization and

GTP hydrolysis are tightly coupled.

2. Protofilament straightens with Tb concentration:

Also in this concentration range, the lower the Tb concentration, the higher the protofilament

curvature at MT tip and the higher the catastrophe frequency.