Tubulin (source code)
= Tubulin
<Tubulin> is the <protein> building material of <microtubules>. Alpha- and beta-<tubulin> form a heterodimer; repeated addition of these units produces polarized protofilaments assembled into a hollow tube. The two ends of a <microtubule> differ in organization and growth behaviour. <GTP> binding and hydrolysis by beta-<tubulin> couple assembly history to stability. <Molecular Biology of the Cell, 4th edition by Bruce Alberts and others>[Chapter 16, Microtubules: tubulin dimers, polarity and dynamic instability]{ref}
This explains how the same material supports both persistent cellular architecture and rapid rearrangement of a <spindle apparatus>. Losing a stabilizing end region can trigger rapid shortening even while soluble <tubulin> remains available. <Fluorescence> measurements of <tubulin> amount alone therefore do not determine how much is assembled, the direction of growth or the lifetime of an individual <microtubule>.
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