Membrane protein structure determination from Paramagnetic Relaxation Enhancement and internuclear distance...

Area of Science:

• Biochemistry
• Structural Biology
• Biophysics

Background:

• Magic angle spinning nuclear magnetic resonance (MAS NMR) is crucial for protein structure determination.
• Spectral overlap in MAS NMR spectra complicates the assignment of cross peaks, hindering structural analysis.

Purpose of the Study:

• To demonstrate the utility of transverse Paramagnetic Relaxation Enhancements (PRE) from 2D MAS NMR spectra for protein structural modeling.
• To develop an improved method for assigning spectral cross peaks in complex protein systems.

Main Methods:

• Utilized a seven-helical membrane protein, Anabaena Sensory Rhodopsin (ASR), as a model system.
• Combined TALOS+ predicted dihedral angles and hydrogen bond restraints with PRE-based restraints to generate an initial structural model.
• Employed an iterative cross-peak assignment process using the generated model as a template.

Main Results:

• Successfully generated a coarse structural model of ASR using combined restraints.
• Facilitated automated assignment of ambiguous internuclear correlations through iterative refinement.
• Achieved convergence to a low root-mean-square-deviation structural model with improved helix packing.

Conclusions:

• Transverse PREs extracted from 2D MAS NMR spectra are effective for protein structure determination and spectral assignment.
• The iterative approach using a PRE-enhanced template model improves structural modeling efficiency and accuracy.
• PREs enhance the packing of helices within alpha-helical bundles, providing valuable insights into membrane protein structure.