Tubulin is the major constituent of microtubules. It exists as a heterodimer consiting of an alpha and a beta subunit. Class II beta tubulin is the major form of tubulin beta in neurons, although it is not neuronal specific. It is found in many other tissues including lung tissue and Schwann cells. It binds two moles of GTP, one at an exchangeable site on the beta chain and one at a nonexchangeable site on the alpha chain.
