The tubuline is the strucutrelle Protéine Microtubule S, a major component of the Cytosquelette. It has a molecular mass of approximately 100 kDa.

Compostion

• the tubuline α of molecular mass from approximately 50 kDa and with a phi of about 5,3 - 5,8, and is related to the GTP.
• the tubuline β of molecular mass from approximately 50 kDa and with a phi of about 5,3 - 5,6 and is related to the GTP, that it with the capacity to hydrolize. It is the state of this sub-unit which defines the state " GTP" or " GDP" tubuline.

These two sub-units, resulting from the expression of two different genes (gene α and gene β), are thus very similar and differ in fact only by some amino-acid (5 to 10% of the chain).

Function: polymerization

The tubuline directs the dynamics of the Microtubule S. Following its concentration in the cell, it will direct polymerization or depolymerization of it.

- If the concentration of tubuline-GTP is raised, of the Dimère S α-ß is polymerized, forming the protofilaments. These protofilaments joins between them over their length and thus forms the microtubule. The assembly of proto-filament can also lead to obtaining a Flagelle, as in the spermatozoa for example.

- If the concentration of tubuline-GTP in the cell is too weak, the protofilaments will be depolymerized and degraded.

In the cell, the microtubules radiate with a cytosolic structure visible with the electron microscope called Centrosome. All the animal cells Eucaryote S have one in their cytoplasm of them; the vegetable cells they have another structure, nonvisible in microscopy, which is called " center organizing microtubules".

Pharmacology

The tubulines are the targets of the Médicament S anti-cancer like the Taxol or the Vinblastine. The Colchicine binds to the tubuline and inhibits the formation of microtubules, immobilizing the Neutrophile S and lowering the Inflammation.

References

• Microtubule Polymerization Dynamics . Arshad Desai and Thimoty J.Mitchison. Ann. Rev. Concealment. Dev. Biol. (1997) 13:83 - 117.