Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 and 15 nm. They are formed by the polymerization of a dimer of two globular proteins, alpha and beta tubulin into protofilaments that can then associate laterally to form a hollow tube, the microtubule. The most common form of a microtubule consists of 13 protofilaments in the tubular arrangement.
Tubulin in molecular biology can refer either to the tubulin protein superfamily of globular proteins, or one of the member proteins of that superfamily. α- and β-tubulins polymerize into microtubules, a major component of the eukaryotic cytoskeleton. Microtubules function in many essential cellular processes, including mitosis. Tubulin-binding drugs kill cancerous cells by inhibiting microtubule dynamics, which are required for DNA segregation and therefore cell division.
Katanin is a microtubule-severing AAA protein. It is named after the Japanese sword called a katana. Katanin is a heterodimeric protein first discovered in sea urchins. It contains a 60 kDa ATPase subunit, encoded by KATNA1, which functions to sever microtubules. This subunit requires ATP and the presence of microtubules for activation. The second 80 kDA subunit, encoded by KATNB1, regulates the activity of the ATPase and localizes the protein to centrosomes. Electron microscopy shows that katanin forms 14–16 nm rings in its active oligomerized state on the walls of microtubules.
In cell biology, microtubule nucleation is the event that initiates de novo formation of microtubules (MTs). These filaments of the cytoskeleton typically form through polymerization of α- and β-tubulin dimers, the basic building blocks of the microtubule, which initially interact to nucleate a seed from which the filament elongates.
Polo-like kinases (Plks) are regulatory serine/threonin kinases of the cell cycle involved in mitotic entry, mitotic exit, spindle formation, cytokinesis, and meiosis. Only one Plk is found in the genomes of the fly Drosophila melanogaster (Polo), budding yeast (Cdc5) and fission yeast (Plo1). Vertebrates and other animals, however, have many Plk family members including Plk1, Plk2/Snk, Plk3/Prk/FnK, Plk4/Sak and Plk5. Of the vertebrate Plk family members, the mammalian Plk1 has been most extensively studied. During mitosis and cytokinesis, Plks associate with several structures including the centrosome, kinetochores, and the central spindle.
In enzymology, a microtubule-severing ATPase (EC 3.6.4.3) is an enzyme that catalyzes the chemical reaction
Tubulin alpha-4A chain is a protein that in humans is encoded by the TUBA4A gene.
Tubulin alpha-1B chain is a protein that in humans is encoded by the TUBA1B gene.
Microtubule-associated protein 1A is a protein that in humans is encoded by the MAP1A gene.
Microtubule-associated protein RP/EB family member 1 is a protein that in humans is encoded by the MAPRE1 gene.
Tubulin alpha-8 chain is a protein that in humans is encoded by the TUBA8 gene.
Katanin p60 ATPase-containing subunit A1 is an enzyme that in humans is encoded by the KATNA1 gene.
Tubulin gamma-2 chain is a protein that in humans is encoded by the TUBG2 gene.
Gamma-tubulin complex component 3 is a protein that in humans is encoded by the TUBGCP3 gene. It is part of the gamma tubulin complex, which required for microtubule nucleation at the centrosome.
Centrin-1 is a protein that in humans is encoded by the CETN1 gene. It belongs to the centrin family of proteins.
Centrosomal protein of 70 kDa is a protein that in humans is encoded by the CEP70 gene. The protein interacts with γ-tubulin through its coiled coil domains to localize at the centrosome. CEP70 is involved in organizing microtubules in interphase cells and is required for proper organization and orientation of the mitotic spindle.
Gamma-tubulin complex component 6 is a protein that in humans is encoded by the TUBGCP6 gene. It is part of the gamma tubulin complex, which required for microtubule nucleation at the centrosome.
Centrosomal protein of 192 kDa, also known as Cep192, is a protein that in humans is encoded by the CEP192 gene. It is the homolog of the C. elegans and D. melanogaster gene SPD-2.
Centrosomal protein of 164 kDa, also known as CEP164, is a protein that in humans is encoded by the CEP164 gene. Its function appears two be twofold: CEP164 is required for primary cilium formation. Furthermore, it is an important component in the response to DNA damage by UV light.
Centrosomal protein of 78 kDa, also known as Cep78, is a protein that in humans is encoded by the CEP78 gene.
