Binding and degradation of heterodimeric substrates by ClpAP and ClpXP

Area of Science:

• Molecular biology
• Protein degradation
• Enzymology

Background:

• ClpA and ClpX are molecular chaperones and regulators of ClpAP and ClpXP proteases.
• These chaperones bind substrates via recognition signals, unfold them using ATP, and translocate them into ClpP for degradation.

Purpose of the Study:

• To investigate the distinct mechanisms by which ClpAP and ClpXP proteases interact with and degrade dimeric protein substrates.
• To elucidate how recognition signals influence substrate binding and degradation by these protease complexes.

Main Methods:

• Single-round binding and degradation experiments were conducted using dimeric RepA substrates (homodimers and heterodimers).
• Substrates were engineered to contain or lack specific ClpA recognition signals.

Main Results:

• ClpAP degraded both subunits of a RepA homodimer in a single binding cycle.
• ClpAP also degraded both subunits of a RepA heterodimer when only one subunit possessed the ClpA recognition signal.
• In contrast, ClpXP degraded both subunits of a dimeric substrate only when both subunits contained a recognition signal.

Conclusions:

• ClpAP and ClpXP exhibit fundamentally different mechanisms for recognizing and binding dimeric substrates.
• The data suggest ClpAP can process substrates even with incomplete signal recognition, while ClpXP requires dual recognition.