Complete Reversible Refolding of a G-Protein Coupled Receptor on a Solid Support

Area of Science:

• Biochemistry
• Structural Biology
• Membrane Protein Research

Background:

• Integral membrane protein folding and stability are poorly understood, with significant knowledge gaps for G protein coupled receptors (GPCRs).
• Complete reversible refolding of membrane proteins, especially GPCRs, remains a significant challenge, with current methods yielding only 40-70% functional recovery from denatured states.

Purpose of the Study:

• To develop and present a novel method for the complete reversible unfolding and refolding of a model GPCR, the β1-adrenergic receptor.
• To achieve 100% recovery of the folded, functional state of the β1-adrenergic receptor after denaturation.

Main Methods:

• Utilized refolding on a solid support to minimize aggregation and unwanted interactions in solution.
• Employed pulse proteolysis, a technique relatively new to membrane protein folding studies.
• Investigated structural and functional changes upon unfolding and refolding using ligand binding assays and protein fluorescence.

Main Results:

• Achieved 100% recovery of the functional β1-adrenergic receptor, matching the ligand binding of the native, unfolded protein.
• Demonstrated complete refolding in n-decyl-β-D-maltoside (DM) micelles from a urea-denatured state.
• Confirmed regain of original helical structure, ligand binding, and protein fluorescence post-refolding.

Conclusions:

• The developed solid-support refolding strategy provides a defined method for controlled refolding and recovery of functional GPCRs.
• This approach offers a solution for stabilizing and recovering other membrane proteins prone to instability and irreversible denaturation.
• Successfully overcame limitations in membrane protein refolding, paving the way for future studies on GPCR structure and function.