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

Dimer of alpha and beta chains. 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 RANBP10

Hematopoietic cell-specific. Major isotype in leukocytes, where it represents 50% of all beta-tubulins

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

• Macrothrombocytopenia, isolated, 1, autosomal dominant (MACTHC1)

  A congenital blood disorder characterized by increased platelet size and decreased number of circulating platelets.