The tail wags the tubulin

Area of Science:

• Cell Biology
• Biochemistry
• Structural Biology

Background:

• Microtubules are essential cytoskeletal polymers involved in cell division, intracellular transport, and cell structure.
• Tubulin, the protein subunit of microtubules, undergoes various post-translational modifications (PTMs) that regulate microtubule function.
• The C-terminal tail (CT) of alpha-tubulin is known to influence microtubule dynamics, but its precise role and the impact of PTMs remain incompletely understood.

Purpose of the Study:

• To elucidate the molecular mechanisms by which the alpha-tubulin C-terminal tail regulates microtubule assembly and stability.
• To investigate the role of post-translational modifications on the alpha-tubulin tail in modulating microtubule properties.
• To provide atomic-level insights into the structural contributions of the alpha-tubulin tail to microtubule architecture.

Main Methods:

• In vitro assembly assays using purified recombinant alpha- and beta-tubulin.
• Biochemical characterization of tubulin polymerization dynamics.
• Molecular dynamics (MD) simulations of microtubule structures with varying C-terminal tail modifications.
• Analysis of structural changes and interaction interfaces within microtubules.

Main Results:

• The alpha-tubulin C-terminal tail directly interacts with adjacent tubulin subunits, stabilizing the microtubule lattice.
• Specific post-translational modifications, such as detyrosination, alter the tail's conformation and reduce its stabilizing interactions.
• Molecular dynamics simulations revealed distinct conformational states of the tail, correlating with altered microtubule stability.
• The study identified key residues within the tail critical for mediating inter-tubulin interactions.

Conclusions:

• The C-terminal tail of alpha-tubulin is a critical determinant of microtubule stability through direct interactions within the microtubule lattice.
• Post-translational modifications of the alpha-tubulin tail act as regulatory switches, fine-tuning microtubule dynamics and cellular functions.
• This work provides a molecular framework for understanding how tubulin PTMs contribute to the functional diversity of microtubules.