This project seeks to define the molecular rules that determine how a new microtubule forms from its building blocks - the αβ-tubulin protein subunits. Microtubules are dynamic polymeric assemblies that organize the insides of cells, mediate faithful segregation of the genetic material during cell division, and provide tracks for motor-based transport. The research will focus on microtubule nucleation, the poorly understood process by which αβ-tubulin units self-assemble to initiate a new microtubule. The project will reveal and quantify how structural and biochemical properties of the individual αβ-tubulin building blocks determine the rate of microtubule nucleation and the sequence of oligomeric intermediates that precede formation of a new microtubule, and how these vary in αβ-tubulins from different species. The project also emphasizes an educational impact. Graduate students working on the project will receive interdisciplinary training that includes quantitative biochemistry and computational modeling. Outreach partnerships with local elementary and middle schools will bring the excitement of doing science to underrepresented and economically disadvantaged students, while providing teachers and their pupils access to high-tech, but relatively inexpensive, digital microscopes to facilitate curiosity-based learning and discovery.
The specific research objective of this proposal is to create a molecular understanding of microtubule nucleation. Dynamic properties of microtubules derive from the biochemical properties of individual αβ-tubulin subunits and their interactions within the polymeric assembly. MT nucleation – the formation of a new polymer from unpolymerized subunits – is a poorly understood behavior that is critical for building MT networks and it is highly regulated by cellular factors. The research will use computational and experimental approaches to address three specific goals: (i) to develop a mechanistic understanding of microtubule nucleation in a simplified setting where αβ-tubulin GTPase activity has been suppressed, (ii) to use Monte Carlo simulations to create a more exact and generalizable description of the biochemical mechanisms that control MT nucleation in a way that can account for the effects of GTPase activity, (iii) to use protein engineering to assemble and trap defined oligomers of αβ-tubulin that would otherwise be too unstable to work with, and to use these oligomers for new kinds of structural, biochemical, and mechanistic studies. All work will be carried out using two different model systems, recombinant yeast and human αβ-tubulin, providing insight into whether and how microtubule nucleation and αβ-tubulin biochemistry vary across species.
This works is jointly funded by the Molecular Biophysics and Cellular Dynamics and Function Clusters of MCB.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
