Characterization of the pH response of disordered tubulin tails.

Abstract

Microtubules, formed by the polymerization of alpha and beta tubulin heterodimers, play an essential role in cell division and motility. The disordered C-terminal tails of each tubulin monomer are major sites of tubulin regulation and, despite being flexible, appear to regulate microtubule dynamics and tubulin interactions with its binding partners. Across species and isoforms, there is a preponderance of acidic amino acids in the C terminal tails, primarily present in polyglutamate tracts. We postulated that these negatively charged patches may lend the tail sensitivity to various protonation states as might be experienced under cellular stress conditions. Using nuclear magnetic resonance (NMR) spectroscopy, an ideal tool to probe the dynamics and properties of small, disordered regions such as the C-terminal tubulin tails, we probed the pH response of alpha and beta tubulin tail peptides from different species. We used point mutations and truncations within the charged regions to probe the robustness of the pH response of these disordered regions. Our results indicate there is a dynamic and attested effect from changes in pH throughout the C-terminal tail of tubulin monomers.