Figure 8. Harmonized assembly and closure during microtubule growth.

(a) Snapshots of the sheet structure during a time span of two subsequent closures of a monomer pair. When a layer at the end of the sheet has been fully filled by newly added tubulins, the seam will be zipped a same length. The blue and red-highlighted structures show two processes of the assembled dimers fulfilling a complete layer and the subsequent seam zipping up. (b) The microtubule end development at the two closures in (a). The two yellow-colored dimers are those finally fulfill a layer and trigger a corresponding closure.