BIOPHYSICAL THEORY AND MODELING |
Metastability of Microtubules Induced by Competing Internal Forces
Viktoria Hunyadi 1 and Imre M. Janosi 1*
1 Department of Physics of Complex Systems, Lorand Eotvos University
* To whom correspondence should be addressed. E-mail: janosi{at}lecso.elte.hu.
Submitted on June 20, 2006
Revised on October 18, 2006
Accepted on 4 January 2007
 |
Abstract |
|---|
Recent modeling efforts to estimate energies of tubulin-tubulin bonds shed light on a delicate balance between competing mechanical forces maintaining microtubule walls. Here we formulate two important refinements to the explanation of bond energetics. Firstly, energy surface calculations in the elastic filament approximation reveal a finite stabilizing barrier assumed simple Lennard-Jones like potential for protein bonds. The presence of a GTP cap represented by straight segments is necessary, as it is predicted for a long time. In the lack of such cap, the protofilaments are either in an absolute stable or absolute instable state. Secondly, our calculations show that this barrier appears only if the mechanical energy associated with the conformational change following GTP hydrolysis (curling energy) is larger than the strength of lateral bonds. The overall energy balance we propose supports continuous assembly of GTP dimers, a metastable state in the presence of a finite GTP cap, and energetically driven disassembly of GDP protofilaments.
Key Words:
bond energetics, catastrophes, conformational change, metastability, microtubules
