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Insights into microtubule catastrophes: the effect of end-binding proteins and force

For each living organism health is ensured by correct functioning of its cells. Cells therefore have elaborate methods for regulation of their proteins.

S.M.J. Kalisch
13 december 2023
Thesis in Leiden Repository

In this thesis we examine a set of highly conserved proteins: microtubules (MTs), which are either in a growing or a shrinking phase, together with the MTs' end-binding proteins mal3, tea2 and tip1. Using total internal reflection fluorescence microscopy we grow these proteins in custom-made, patterned flow chambers. We also examine the influence of force on MTs by letting them grow against obstacles, using the same microscopy technique or optical tweezers.Focusing on the switch from a growing to a shrinking state, a so-called catastrophe, we investigate the trigger of a catastrophe. For this we create distributions of the length of MT growth phases and fit them with several functions. All of the functions describe reactions involving several steps. We find that MTs need two steps until a catastrophe, a process which is sped up by the end-binding proteins as well as by force. Besides, we also present another model for MT catastrophe in which noisy growth together with a specific state of the microtubule tip are capable to explain a lot of the published MT data.

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