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Putting the "tube" in microtubules

Tubulin is a heterodimer protein, meaning it is comprised of a pair of polypeptide chains, called monomers, that differ slightly in the sequence of their amino acids. Polypeptide chains of tubulin form tiny hollow fibers called microtubules that intermesh to provide a cell with its cytoskeletal framework.

Research team constructs computer models of proteins

Kenneth Downing (left), Eva Nogales, and Robert Glaeser have been using supercomputers to construct 3-D models of proteins.

 

Thanks to the flexibility of the tubulin protein, microtubules can shift through a variety of formations. This formation shifting is what enables a cell to carry out such vital processes as mitosis (cell division) and the transport of particles and organelles inside the cell.

Knowing the atomic structure of tubulin is important to scientists just for its critical role in the life of a cell. However, scientific interest in tubulin intensified when taxol, a natural substance found in the bark of the Pacific yew tree was shown in clinical tests to be an effective treatment for a number of cancers including ovarian, breast, and lung. (The name taxol has been trademarked by Bristol-Myers Squibb.)

Cancer occurs when cell division runs amok. By binding to tubulin and causing the protein to lose its flexibility, taxol prevents a cell from dividing. With better knowledge of tubulin structure and its interaction with taxol scientists believe that an even more effective anti-cancer drug, one that interacts only with the tubulin of cancerous cells, could be synthesized.

The all-important taxol binding site has now been identified in the high-resolution 3-D model of tubulin created by researchers Eva Nogales, Ken Downing, and Sharon Wolf of Berkeley Lab's Life Sciences Division.

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Ernest Orlando Lawrence Berkeley National Laboratory