title: Mechanochemical model of microtubule structure and self-assembly kinetics.
abstract: Microtubule self-assembly is largely governed by the chemical kinetics and thermodynamics of tubulin-tubulin interactions. An important aspect of microtubule assembly is that hydrolysis of the beta-tubulin-associated GTP promotes protofilament curling. Protofilament curling presumably drives the transition from tip structures associated with growth (sheetlike projections and blunt ends) to those associated with shortening (rams' horns and frayed ends), and transitions between these structures have been proposed to be important for growth-shortening transitions. However, previous models for microtubule dynamic instability have not considered such structures or mechanics explicitly. Here we present a three-dimensional model that explicitly incorporates mechanical stress and strain within the microtubule lattice. First, we found that the model recapitulates three-dimensional tip structures and rates of assembly and disassembly for microtubules grown under standard conditions, and we propose that taxol may stabilize microtubule growth by reducing flexural rigidity. Second, in contrast to recent suggestions, it was determined that sheetlike tips are more likely to undergo catastrophe than blunt tips. Third, partial uncapping of the tubulin-GTP cap provides a possible mechanism for microtubule pause events. Finally, simulations of the binding and structural effects of XMAP215 produced the experimentally observed growth and shortening rates, and tip structure.
authors.affiliation: Department of Biological Sciences, Lehigh University, Bethlehem, PA, USA.
authors.forename: Vincent
authors.initials: V
authors.lastname: VanBuren
authors.forename: Lynne
authors.initials: L
authors.lastname: Cassimeris
authors.forename: David J
authors.initials: DJ
authors.lastname: Odde
mesh_terms: D001703:Biophysics / Q000379:methods; D003198:Computer Simulation; D019281:Dimerization; D006153:Guanosine Diphosphate / Q000737:chemistry; D006160:Guanosine Triphosphate / Q000737:chemistry; D006358:Hot Temperature; D007700:Kinetics; D008870:Microtubules / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D015233:Models, Statistical; D011485:Protein Binding; D013314:Stress, Mechanical; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors; D014404:Tubulin / Q000737:chemistry
chemical_list: D014404:Tubulin; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate