tubulin

(TOO-byuh-lin) One of a group of proteins found in high levels in the cell cytoplasm (fluid inside a cell but outside the cell's nucleus). Tubulins are the building blocks of microtubules (narrow, hollow tubes inside a cell), which are involved in cell division and cell movement. Certain anticancer drugs bind to and block the formation or function of tubulins, which may block cell division.

The major protein component of the microtubules of eukaryotic cells.