Tubulin is the major constituent of microtubules. The gamma chain is found at microtubule organizing centers (MTOC) such as the spindle poles or the centrosome; suggesting that it is involved in the minus-end nucleation of microtubule assembly. Required for oocyte activation and consequently for organization of the female meiotic spindle. Essential for centrosome organization and assembly of biastral mitotic spindles in embryos. {ECO:0000269|PubMed:9155007; ECO:0000269|PubMed:9698447}.