Molecular Dissection of the Tubulin C-Terminal Tails by NMR

Abstract

Microtubules made from α-β tubulin heterodimers are important for cell migration, long range transport in cells, and cell division. The disordered C-terminal tails (CTT) are a primary site of tubulin regulation. Tubulin CTT affect microtubule (MT) length dynamics and mechanical properties, and are a major site of tubulin post-translational modification which regulates tubulin's binding interactions. Major questions remain about the molecular mechanism of tubulin CTT function and regulation. We have developed techniques to use nuclear magnetic resonance spectroscopy to study the binding and regulation by post-translational modification of the tubulin CTT. Previous work has shown contradictory results for protein interactions with isolated CTT peptides versus CTT connected to full tubulin dimers. Therefore, we compared chemical shift values of CTT peptides in isolation and when connected to the dimer. We found significant differences in the chemical shift values, indicating different average CTT environment in each context. Our results suggest that the CTT dynamically interact with the ordered dimer surface in ways that can modify CTT and/or MT behavior, consistent with previous results showing that CTT affect MT polymerization and mechanical properties. This system will enable study of the molecular mechanisms of CTT effects on MT regulation.