Structural insight into the XTACC3/XMAP215 interaction from CD and NMR studies on model peptides

Area of Science:

• Cell Biology
• Structural Biology
• Biochemistry

Background:

• TACC3 (Transforming acidic coiled-coil containing protein 3) is a centrosomal adaptor protein crucial for mitotic spindle assembly.
• It interacts with chTOG/XMAP215, a protein that promotes microtubule growth by adding tubulin dimers.
• Existing 3D models of this interaction lack detailed structural information.

Purpose of the Study:

• To elucidate the structural basis of the TACC3-chTOG/XMAP215 interaction at atomic resolution.
• To investigate the role of peptide structure and stoichiometry in complex formation.
• To analyze the impact of TACC3 mutations on structural integrity and interaction.

Main Methods:

• Utilized circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy.
• Studied four distinct peptides derived from TACC3 and chTOG/XMAP215.
• Analyzed peptides individually, in pairs, and in trios to determine binding prerequisites.

Main Results:

• Single peptides and peptide pairs did not form stable coiled-coil structures.
• The simultaneous presence of all studied peptides (preformed helices) was necessary for complex formation.
• NMR data allowed the proposal of a simplified 3D model for the TACC3-chTOG/XMAP215 interaction.
• Mutations in TACC3 essential for activity did not alter peptide structure, suggesting non-structural factors mediate interaction.

Conclusions:

• The TACC3-chTOG/XMAP215 interaction requires the simultaneous assembly of multiple helical peptide components.
• The proposed 3D model provides atomic-level insights into the complex.
• TACC3 mutations affecting activity likely disrupt specific binding interfaces rather than overall structure.