Docking phospholipase A2 on membranes using electrostatic potential-modulated spin relaxation magnetic resonance

Area of Science:

• Biophysics
• Biochemistry
• Membrane Protein Dynamics

Background:

• Peripheral membrane proteins play crucial roles in cellular signaling and function.
• Understanding the precise binding interactions of secreted enzymes like bee venom phospholipase A2 (bvPLA2) with membranes is essential for elucidating their biological mechanisms.

Purpose of the Study:

• To develop and apply a novel biophysical method to precisely determine the membrane-binding orientation and interfacial surface of bee venom phospholipase A2.
• To investigate the interaction of bvPLA2 with lipid bilayers using site-selective spin labeling and electron paramagnetic resonance (EPR) spectroscopy.

Main Methods:

• Site-selective spin labeling of a peripheral membrane protein (bvPLA2) with nitroxide spin probes.
• Electron paramagnetic resonance (EPR) spectroscopy measurements in the presence and absence of membranes.
• Utilizing a water-soluble spin relaxant (chromium oxalate) to probe accessibility and distance from the membrane surface.
• Applying Poisson-Boltzmann equation-based theory to interpret EPR relaxation data and determine spin probe-membrane distances.

Main Results:

• The developed EPR spectroscopy method successfully determined the interfacial binding surface of bee venom phospholipase A2 on the membrane.
• The study quantified the distance (up to tens of angstroms) between the protein-bound spin probe and the membrane surface.
• The findings provide a detailed picture of how bvPLA2 associates with the membrane interface.

Conclusions:

• The novel EPR spectroscopy approach provides a powerful tool for characterizing the membrane interactions of peripheral proteins.
• The results elucidate the specific interfacial binding mode of bee venom phospholipase A2, contributing to the understanding of its enzymatic activity and membrane association.
• This methodology can be extended to study other peripheral membrane proteins and their interactions with lipid bilayers.