Tubulin is a globular protein that polymerizes to form microtubules, the filamentous network that helps maintain cell structure and participates in cell movement and division. Tubulin is fluorescently labeled without the use of antibodies in the digital image presented below. The living cells are expressing a recombinant tubulin, which contains a small tetracysteine motif that has a high affinity for a custom designed fluorescein-like molecule called FlAsH that binds to the biopolymer. The nuclear DNA is counterstained in blue.

Tubulin Specimen: Fluorescently labeled cell culture Technique: Confocal Microscopy

Initially discovered in the 1950s, the first three-dimensional atomic model of tubulin was built by a team of scientists working for the United States Department of Energy after thirty years of attempts to unravel the mystery of the protein’s structure. A heterodimer, tubulin consists of a pair of polypeptide chains that have different amino acid sequences. Described as alpha tubulin and beta tubulin, both monomers exhibit three functional components, including one that binds to other proteins, one that connects to nucleotides, and one that attaches to drugs.

Tubulin has held sustained significance for researchers because it is the flexibility of the substance that enables microtubules to shift through various formations during mitosis and intracellular transport. Interest in the structure of tubulin has become even more prominent recently because it shows signs of interacting with taxol, a substance found in the bark of the Pacific yew tree. Taxol works with tubulin by binding to the protein in a manner that causes the structure to lose its flexibility, thereby inhibiting the excessive cellular division characteristic of cancer. More extensive research is needed, however, in order that more effective anti-cancer medications may be developed.