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Related Experiment Video

Updated: May 6, 2026

Purification of Hsp104, a Protein Disaggregase

Purification of Hsp104, a Protein Disaggregase

Published on: September 30, 2011

Slippery substrates impair ATP-dependent protease function by slowing unfolding.

Daniel A Kraut¹

¹From the Department of Chemistry, Villanova University, Villanova, Pennsylvania 19085.

The Journal of Biological Chemistry

|October 24, 2013

Summary

Low complexity sequences in protein substrates slow degradation by ATP-dependent proteases like the proteasome and ClpXP. This finding reconciles previous contradictory results on substrate release and unfolding rates, revealing a shared mechanism across species.

Keywords:

ATP-dependent Protease Enzyme Kinetics Pre-steady-state Kinetics Proteasome Protein Degradation Protein Denaturation Protein Evolution Protein Translocation Protein Unfolding

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Area of Science:

Biochemistry
Molecular Biology
Proteostasis

Background:

ATP-dependent proteases mediate essential protein degradation.
Substrate sequence complexity can disrupt protease processivity, leading to premature release or incomplete degradation.
Previous studies showed conflicting effects of low complexity regions on proteasome and ClpXP activity.

Purpose of the Study:

To reconcile apparently contradictory findings on how substrate low complexity regions affect ATP-dependent protease activity.
To investigate the mechanism by which glycine-rich regions (GRR) and glycine-alanine repeats (GAr) impact substrate unfolding and release.
To determine if the proteasome and ClpXP share common mechanisms for regulating degradation processivity.

Main Methods:

Reanalysis of published ClpXP data concerning glycine-alanine repeats (GAr) in substrates.
Comparative analysis of substrate unfolding and release rates mediated by the proteasome and ClpXP.
Investigating the impact of low complexity sequences on protein degradation processivity.

Main Results:

Reanalysis indicates that GArs, similar to GRR, slow substrate unfolding and degradation by ClpXP.
Low complexity sequences primarily affect the unfolding rate, not the release rate, for both proteasome and ClpXP.
Contradictory previous findings are resolved by considering the effect on unfolding versus release.

Conclusions:

The proteasome and ClpXP share a conserved mechanism for regulating degradation processivity via substrate sequence features.
Low complexity sequences act as regulators of unfolding rates, influencing the overall efficiency of protein degradation.
Understanding these mechanisms is crucial for comprehending protein homeostasis and disease.