mikrotubulusorganisationscentrum

Mikrotubulus, or microtubule, is a hollow, cylindrical polymer that forms a major component of the cytoskeleton in most eukaryotic cells. It is about 25 nanometers in diameter and is built from α- and β-tubulin heterodimers arranged into linear protofilaments, typically 13 of which associate to form the hollow tube. Microtubules are polarized, with a fast-growing plus end and a slower, more stable minus end, and they exhibit dynamic instability, switching between growth and shrinkage.

Microtubules serve as tracks for intracellular transport. Motor proteins such as kinesin move cargo toward the plus end, while dynein travels toward the minus end. This system supports organelle positioning, vesicle trafficking, and long-range transport in neurons. Microtubules also form the mitotic spindle during cell division and play a critical role in chromosome alignment and separation. They contribute to the organization of the cell cortex and participate in the formation and function of cilia and flagella, where the axoneme organizes their motility.

Nucleation of microtubules occurs at microtubule organizing centers (MTOCs), such as the centrosome in animal cells, where γ-tubulin ring complexes template new filaments. The dynamics of growth are regulated by GTP-tubulin incorporation, which, after hydrolysis, can lead to catastrophe and rescue events. Microtubule-associated proteins stabilize or destabilize filaments and modulate interactions with motors and other cytoskeletal networks. Clinically, microtubules are targeted by anticancer drugs like taxanes and vinca alkaloids, which disrupt polymerization dynamics and mitotic progression.