Chaperonin complexes monitored by ion mobility mass spectrometry.

Area of Science:

• Structural biology
• Biophysical chemistry
• Mass spectrometry

Background:

• High-resolution structural biology techniques face challenges in analyzing macromolecular protein assemblies.
• Native mass spectrometry (MS) and ion mobility MS (IM-MS) offer new avenues for structural insights.

Purpose of the Study:

• To apply IM-MS to study chaperonin complexes during substrate folding.
• To validate the retention of solution-phase structural properties in the gas phase using IM-MS.
• To investigate the impact of charge state reduction on chaperonin complex structure and IM-MS analysis.

Main Methods:

• Ion mobility mass spectrometry (IM-MS) was used to analyze chaperonin complexes.
• Collision cross sections were measured to infer gas-phase ion shapes and volumes.
• Native MS was employed to study protein assemblies under various charge states.

Main Results:

• Chaperonin complexes, including those with substrates, retain their solution-phase structures in the gas phase.
• Substrate burial within the GroEL cavity was confirmed in the gas phase.
• Ternary complex dimensions were comparable to empty GroEL-GroES complexes.
• Reduced charge states led to more compact chaperonin complexes, improving ion mobility separation without altering relative collision cross section differences.

Conclusions:

• IM-MS is a powerful tool for studying the structural integrity of protein assemblies.
• Native MS and IM-MS can accurately represent solution-phase structures of macromolecular complexes in the gas phase.
• Charge state manipulation can optimize IM-MS analysis of large protein assemblies.