The cryo-electron microscopy structure of huntingtin

Area of Science:

• Structural biology
• Molecular cell biology
• Neuroscience

Background:

• Huntingtin (HTT) is a large protein essential for development, involved in cellular processes like transport and transcription.
• HTT acts as a protein-protein interaction hub, but its comprehensive biological functions remain unclear.
• Huntington's disease arises from mutations in the HTT gene, yet detailed structural information is limited.

Purpose of the Study:

• To determine the high-resolution structure of full-length human Huntingtin (HTT) protein.
• To elucidate the structural interaction between HTT and HTT-associated protein 40 (HAP40).
• To provide structural basis for understanding HTT's cellular functions and disease mechanisms.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was employed to determine the structure.
• The study focused on the complex of full-length human HTT with HAP40.
• Structural analysis was performed to an overall resolution of 4 Å.

Main Results:

• The structure of full-length human HTT in complex with HAP40 was determined at 4 Å resolution.
• HTT comprises three main domains, largely α-helical, with HEAT repeats in the N- and C-terminal domains.
• HAP40, also α-helical, binds within a cleft of HTT, stabilizing its conformation through hydrophobic and electrostatic interactions.

Conclusions:

• The determined structure rationalizes existing biochemical data on HTT function.
• This structural information provides a foundation for understanding HTT's diverse cellular roles.
• The findings pave the way for future research into HTT-related cellular mechanisms and potential therapeutic targets.