HDX-guided EPR spectroscopy to interrogate membrane protein dynamics.

Area of Science:

• Biophysics
• Structural Biology
• Membrane Protein Dynamics

Background:

• Pulsed electron paramagnetic resonance (EPR) spectroscopy offers high-resolution insights into protein dynamics.
• Integral membrane proteins present unique challenges for structural and dynamic studies.
• Site-directed spin labeling is crucial for EPR-based investigations of protein structure and function.

Purpose of the Study:

• To describe detailed protocols for the purification and site-directed spin labeling of integral membrane proteins.
• To demonstrate the utility of peptide-level Hydrogen-Deuterium Exchange Mass Spectrometry (HDX-MS) in guiding EPR experiments.
• To showcase the application of various EPR techniques (cwEPR, DEER/PELDOR, ESEEM) for interrogating membrane protein dynamics using the MscL channel as a model system.

Main Methods:

• Site-directed spin labeling of integral membrane proteins.
• Peptide-level Hydrogen-Deuterium Exchange Mass Spectrometry (HDX-MS) for guiding spin labeling strategies.
• Pulsed EPR techniques including Electron Spin Echo Envelope Modulation (ESEEM), DEER/PELDOR, and continuous wave (cw) EPR.
• Utilizing the pentameric MscL channel as a model system for membrane protein dynamics studies.

Main Results:

• Established protocols for preparing and labeling integral membrane proteins for EPR studies.
• Demonstrated the effectiveness of HDX-MS in optimizing residue-specific spin labeling for EPR accessibility measurements.
• Successfully applied cwEPR, DEER/PELDOR, and ESEEM spectroscopies to resolve dynamic motions within the MscL channel.

Conclusions:

• The described protocols provide a robust framework for high-resolution analysis of integral membrane protein dynamics using EPR.
• Integrating HDX-MS with site-directed spin labeling and EPR spectroscopy enables precise interrogation of protein structure-function relationships.
• These advanced EPR methodologies are powerful tools for understanding the complex dynamics of membrane proteins in their native-like environments.