InterPro domain: IPR002452

Microtubules are polymers of tubulin, a dimer of two 55kDa subunits, designated alpha and beta [ 1 , 2 ]. Within the microtubule lattice, alpha-betaheterodimers associate in a head-to-tail fashion, giving rise to microtubule polarity. Fluorescent labelling studies have suggested that tubulin isoriented in microtubules with beta-tubulin toward the plus end [ 3 ]. For maximal rate and extent of polymerisation into microtubules, tubulin requires GTP. Two molecules of GTP are bound at different sites, termed N and E. At the E (Exchangeable) site, GTP is hydrolysed during incorporationinto the microtubule. Close to the E site is an invariant region rich in glycine residues, which is found in both chains and is thought to controlaccess of the nucleotide to its binding site [ 4 ].

Most species, excepting simple eukaryotes, express a variety of closely related alpha- and beta-isotypes. A third family member, gamma tubulin, hasalso been identified in a number of species [ 5 ].

This entry represents alpha tubulin.

1. Molecular biology and genetics of tubulin. Annu. Rev. Biochem. 54, 331-65
2. Diversity among tubulin subunits: toward what functional end? Cell Motil. Cytoskeleton 16, 159-63
3. Localization of an exchangeable GTP binding site at the plus end of microtubules. Science 261, 1044-7
4. Tubulin sequence region beta 155-174 is involved in binding exchangeable guanosine triphosphate. J. Biol. Chem. 262, 15472-5
5. Gamma-tubulin: the hub of cellular microtubule assemblies. Bioessays 15, 637-43