Tunable microsecond dynamics of an allosteric switch regulate the activity of a AAA+ disaggregation machine

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Large protein machines, such as ClpB, are regulated via allosteric communication.
• ClpB is a hexameric AAA+ machine crucial for rescuing aggregated proteins.
• The middle (M) domain of ClpB, a coiled-coil structure, is implicated in binding the co-chaperone DnaK and regulating activity.

Purpose of the Study:

• To investigate the role of ultrafast conformational dynamics in the allosteric regulation of the ClpB protein machine.
• To determine the structural states and dynamics of the ClpB M domain during the chaperone cycle.

Main Methods:

• Single-molecule Förster Resonance Energy Transfer (smFRET) spectroscopy was employed to probe the M domain dynamics.
• Structural determination of the M domain states was performed.

Main Results:

• The ClpB M domain was observed to undergo ultrafast transitions between two distinct structural states on the microsecond timescale.
• These M-domain dynamics are significantly faster than the overall ClpB activity, functioning as a continuous, tunable switch.
• Allosteric interactions, including nucleotide binding, DnaK binding, and substrate binding, were found to modulate these M-domain dynamics.

Conclusions:

• Ultrafast conformational dynamics are integral to the allosteric regulation of ClpB.
• This dynamic regulatory mode enables rapid cellular adaptation.
• Such dynamic control mechanisms may represent a general principle for regulating cellular machineries.