Tubulin is the major constituent of microtubules, a cylinder consisting of laterally associated linear protofilaments composed of alpha- and beta-tubulin heterodimers. Microtubules grow by the addition of GTP-tubulin dimers to the microtubule end, where a stabilizing cap forms. Below the cap, tubulin dimers are in GDP-bound state, owing to GTPase activity of alpha-tubulin

Heterodimer of alpha and beta chains (PubMed:26637975). A typical microtubule is a hollow water-filled tube with an outer diameter of 25 nm and an inner diameter of 15 nM. Alpha-beta heterodimers associate head-to-tail to form protofilaments running lengthwise along the microtubule wall with the beta-tubulin subunit facing the microtubule plus end conferring a structural polarity.

Microtubules usually have 13 protofilaments but different protofilament numbers can be found in some organisms and specialized cells. Interacts with CIMAP3 (PubMed:20643351). Interacts with DIAPH1 (PubMed:23325789).

Interacts with MX1 (By similarity). May interact with RNABP10 (By similarity). Interacts with CFAP157 (By similarity).

Nascent tubulin polypeptide interacts (via beta-tubulin MREI motif) with TTC5/STRAP; this interaction results in tubulin mRNA-targeted degradation (PubMed:31727855)

Ubiquitously expressed with highest levels in spleen, thymus and immature brain

The highly acidic C-terminal region may bind cations such as calcium

The MREI motif is common among all beta-tubulin isoforms and may be critical for tubulin autoregulation

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