Microtubule's conformational cap

The molecular mechanisms that allow elongation of the unstable microtubule lattice remain unclear. It is usually thought that the GDP-liganded tubulin lattice is capped by a small layer of GTP- or GDP-P-i-liganded molecules, the so called "GTP-cap". Here, we point-out that the elastic properties of the microtubule lattice cause a difference in stability between the elongat ing tubulin sheet and the completed microtubule wall. The implications of o ur observations for microtubule structure and dynamics are discussed.