Tubulin Beta (TUBb)

To form microtubules, the dimers of α- and β-tubulin bind to GTP and assemble onto the ends of microtubules while in the GTP-bound state. After being incorporated into the microtubule, the bound molecule of GTP will hydrolyse into GDP. Although both subunits bind GTP, only the β-subunit has GTPase activity; that is, β-tubulin can hydrolyse GTP to GDP whereas α-tubulin cannot. Whether the β-tubulin member of the tubulin dimer is bound to GTP or GDP influences the stability of the dimer in the microtubule. Dimers bound to GTP tend to assemble into microtubules, while dimers bound to GDP tend to fall apart; thus, this GTP cycle is essential for the dynamic instability of the microtubule. Class III β-tubulin‎ is a microtubule element expressed exclusively in neurons, and is a popular identifier specific for neurons in nervous tissue.