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Biochemistry. 2011 Oct 11;50(40):8636-44. doi: 10.1021/bi2005174. Epub 2011 Sep 16.

Design, overexpression, and purification of polymerization-blocked yeast αβ-tubulin mutants.

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Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States.


Microtubule dynamics play essential roles in intracellular organization and cell division. They result from structural and biochemical properties of αβ-tubulin heterodimers and how these polymerizing subunits interact with themselves and with regulatory proteins. A broad understanding of the underlying mechanisms has been established, but fundamental questions remain unresolved. The lack of routine access to recombinant αβ-tubulin represents an obstacle to deeper insight into αβ-tubulin structure, biochemistry, and recognition. Indeed, the widespread reliance on animal brain αβ-tubulin means that very few in vitro studies have taken advantage of powerful and ordinarily routine techniques like site-directed mutagenesis. Here we report new methods for purifying wild-type or mutant yeast αβ-tubulin from inducibly overexpressing strains of Saccharomyces cerevisiae. Inducible overexpression is an improvement over existing approaches that rely on constitutive expression: it provides higher yields while also allowing otherwise lethal mutants to be purified. We also designed and purified polymerization-blocked αβ-tubulin mutants. These "blocked" forms of αβ-tubulin give a dominant lethal phenotype when expressed in cells; they cannot form microtubules in vitro and when present in mixtures inhibit the polymerization of wild-type αβ-tubulin. The effects of blocking mutations are very specific, because purified mutants exhibit normal hydrodynamic properties, bind GTP, and interact with a tubulin-binding domain. The ability to overexpress and purify wild-type αβ-tubulin, or mutants like the ones we report here, creates new opportunities for structural studies of αβ-tubulin and its complexes with regulatory proteins, and for biochemical and functional studies of microtubule dynamics and its regulation.

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