Structural basis of aggregate binding by the AAA+ disaggregase ClpG.

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Protein aggregation is a major cellular challenge during heat stress.
• ATP-dependent AAA+ disaggregases are crucial for rescuing aggregated proteins.
• The specific recognition mechanisms of protein aggregates by disaggregases remain poorly understood.

Purpose of the Study:

• To elucidate the structural basis of aggregate recognition by the N1 domain of the bacterial AAA+ disaggregase ClpG.
• To understand how disaggregases selectively target aggregated proteins over soluble non-native proteins.

Main Methods:

• NMR spectroscopy was used to determine the core structure of the N1 domain.
• Analysis of mixed hexamers with varying N1 domain content was performed.
• Structure-function relationships of conserved hydrophobic residues were investigated.

Main Results:

• The N1 domain possesses a Zn2+-coordination site essential for structural integrity and function.
• Conserved hydrophobic residues on a β-strand of N1 are critical for aggregate targeting and disaggregation.
• At least four N1 domains within a AAA+ ring are required for high disaggregation activity, suggesting avidity effects.

Conclusions:

• Disaggregases recognize protein aggregates through simultaneous contacts with multiple hydrophobic patches on the aggregate surface via their N1 domains.
• This multi-contact binding mode ensures selective targeting of aggregates while sparing soluble proteins.
• The findings define a key recognition principle for protein disaggregation under stress conditions.