Integrated Structural Biology for α-Helical Membrane Protein Structure Determination

Area of Science:

• Structural biology
• Computational biology
• Biophysics

Background:

• Limited experimentally determined structures exist for integral, α-helical, multi-span membrane proteins.
• The conformational space of membrane proteins is vast and complex.
• Previous development of the BCL::MP-Fold algorithm for de novo membrane protein structure prediction.

Purpose of the Study:

• To present a case study on determining the rhodopsin fold using integrated experimental restraints.
• To demonstrate the effectiveness of combining sparse and/or low-resolution data from multiple techniques.
• To establish a protocol for predicting unknown membrane protein folds with limited experimental data.

Main Methods:

• Utilized the BCL::MP-Fold algorithm for sampling conformational space.
• Integrated sparse and low-resolution restraints from electron microscopy, electron paramagnetic resonance spectroscopy, and nuclear magnetic resonance spectroscopy.
• Employed knowledge-based potentials to guide the assembly of predicted secondary structure elements.

Main Results:

• Simultaneous incorporation of orthogonal experimental restraints significantly improved sampling accuracy.
• Successfully identified the correct rhodopsin fold.
• Achieved a protein size-normalized transmembrane root-mean-square deviation as low as 1.2 Å.

Conclusions:

• The developed protocol enables accurate membrane protein fold determination with limited experimental restraints.
• This approach significantly enhances the ability to solve structures of challenging membrane proteins.
• The method is applicable to a wide range of unknown membrane protein structures.