Figure 4. Lattice defects can help recruit MAPs that regulate microtubule dynamics.

(i) Sites of lattice damage can be repaired through the incorporation of GTP-tubulin (green spheres) from solution. These GTP-islands on the lattice help increase microtubule lengths and lifetimes by recruiting microtubule growth promoters (blue watering can) or by serving as points of rescue during subsequent catastrophe events. (ii) Lattice defects (orange spheres) can recruit microtubule severing enzymes (red scissors) to change microtubule density in an array. Severed fragments can either increase total microtubule mass by serving as templates for further polymerization, or be disassembled.