Intrinsic Dynamics of the ClpXP Proteolytic Machine Using Elastic Network Models

Area of Science:

• Biochemistry
• Molecular Biology
• Biophysics

Background:

• The ClpXP complex is an ATP-dependent protease in the mitochondrial matrix, crucial for degrading protein substrates.
• Its precise translocation and degradation mechanisms remain debated, with models including sequential residue translocation (SC/2R, SC/6R) and probabilistic approaches.
• Discrepancies between structural and functional studies necessitate advanced biophysical-computational methods to elucidate kinetics and thermodynamics.

Purpose of the Study:

• To investigate the intrinsic dynamics of the ClpXP complex during substrate hydrolysis using biophysical approaches.
• To explore theoretically probable hydrolysis mechanisms and their relation to substrate translocation.
• To reconcile structural and functional data through computational modeling.

Main Methods:

• Application of elastic network models (ENM) to study the ClpXP complex dynamics.
• Analysis of the stabilization role of the ClpP region and its impact on pore flexibility.
• Molecular dynamics simulations to assess substrate passage and pore behavior.

Main Results:

• ENM models indicate the ClpP region stabilizes the ClpXP complex, enhancing pore flexibility and substrate interaction.
• The assembled complex may adopt a stable configuration, increasing domain rigidity while maintaining pore flexibility.
• Molecular dynamics suggest substrate passage equivalent to approximately 3 residues, involving simultaneous pore unfolding and bottleneck folding.

Conclusions:

• Biophysical and computational models provide insights into the ClpXP complex's translocation mechanism.
• The findings suggest a non-strictly sequential translocation mechanism, influenced by thermodynamic, structural, and configurational factors.
• The study highlights the interplay between protein unfolding, pore dynamics, and substrate degradation in the mitochondrial matrix.