Tubulin
From Free net encyclopedia
Tubulin is the protein which makes up microtubules. Microtubules are assembled from dimers of α- and β-tubulin. Each of these subunits has three domains. γ-tubulin is important in the nucleation and polar orientation of microtubule. Tubulin binds GTP and assembles onto the (+) ends of microtubules in the GTP-bound state. Once assembled into microtubules, it hydrolyzes GTP into GDP. Although both subunits bind GTP, only the β-subunit has GTPase activity; that is, β-tubulin can hydrolize GTP to GDP whereas α-tubulin cannot. The GDP-bound form of tubulin will disassemble from the tip of a microtubule, though it will not spontaneously fall out of the middle. This GTP cycle is essential for the dynamic instability of the microtubule.
Tubulin was long thought to be specific to eukaryotes. Recently, however, the prokaryotic cell division protein FtsZ was shown to be evolutionarily related to tubulin.
Delta and epsilon tubulin have been found to localize at centrioles and may play a role in forming the mitotic spindle during mitosis.
Alpha and Beta Tubulins are proteins that have a molecular weight of approximately 55 kiloDaltons (kDa) each.
Pharmacology
Tubulins are targets for anticancer drugs like Taxol® and the "Vinca alkaloid" drugs such as vinblastine and vincristine. The anti-gout agent colchicine binds to tubulin and inhibits microtubule formation, arresting neutrophil motility and decreasing inflammation.
See also
Template:Cytoskeletal Proteinsde:Tubulin es:Tubulina fr:Tubuline nl:Tubuline ja:チューブリン no:Tubulin pl:Tubulina pt:Tubulina ru:Тубулин