Influence of nucleotide state on tubulin protofilaments
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Microtubules are filaments within cells that play important roles in intracellular transport, cell division, and overall structural support. Microtubules are composed of tubulin dimers of α- and β-tubulin. The dimers polymerize at the (+) end of the microtubule to cause microtubule growth. β-tubulin must be bound to GTP for dimers to polymerize effectively. Microtubules will undergo catastrophic fraying and depolymerization at the (+) end when only GDP-bound tubulin is present. GTP- and GDP-bound dimers in solution seem to exist in a slightly bent state, while they must straighten to polymerize in the microtubule. While the effect of GTP on microtubule stability is clear, it is not so clear exactly how GTP influences the structural integrity of the microtubule, whether it causes conformational changes in the tubulin that prepare the tubulin for polymerization, or whether it facilitates the structural switch upon polymerization. Analysis of computer simulations of protofilaments in either the GTP- or GDP-bound state could elucidate how these nucleotide states affect the curvature of intra and inter dimer linkages and the force required for straightening. Our analysis indicated that nucleotide state did not influence the curvature or flexibility of solvated protofilaments in a way to facilitate polymerization. The GTP-bound protofilament had greater curvature by the end of simulation. Further analysis of protofilaments aligned to a microtubule image or with lateral contacts in place is recommended.
Davied, Eric (2014). Influence of nucleotide state on tubulin protofilaments. Undergraduate Research Scholars Program. Available electronically from