What is the function of XMAP215?
Microtubule growth in cells exceeds intrinsic tubulin addition rate due to polymerase action of Dis1 ch-TOG XMAP215 family enhancing incorporation efficiency. XMAP215 contains five Tumor Overexpressed Gene TOG domains each with two HEAT repeats capable of binding free alpha beta tubulin dimers with micromolar affinity. Mechanism involves processive tracking: TOG array recruits soluble dimers tethers to plus end via interaction with EB1 and lattice then delivers dimers to growing tip in orientation favoring incorporation increasing growth rate several fold. Function does not require ATP hydroly
Ref: Al-Bassam & Chang, Trends Cell Biol 2011 – XMAP215 polymerase binds tubulin dimers enhances polymerization rate.