Tubulin alpha-1B chain is a protein that in humans is encoded by the TUBA1B gene. TUBA1B has been shown to interact with PIK3R1. Antibodies against tubulin alpha 1b can be used as markers for microtubules and spindles. Tubulin is the major constituent of microtubules. It binds two moles of GTP, one at an exchangeable site on the beta chain and one at a non-exchangeable site on the alpha chain.