Backbone assignment of proteins with known structure using residual dipolar couplings

Area of Science:

• Structural biology
• Biophysics
• Nuclear Magnetic Resonance (NMR) spectroscopy

Background:

• Protein resonance assignment is crucial for studying protein-ligand interactions and dynamics using NMR.
• Accurate assignment facilitates structural and functional insights into proteins.

Purpose of the Study:

• To demonstrate how incorporating experimental residual dipolar couplings (RDCs) enhances protein backbone resonance assignment.
• To evaluate the effectiveness of RDC-enhanced assignment for proteins of varying sizes and with potentially incomplete data.

Main Methods:

• Matching experimental RDCs to values back-calculated from known 3D protein structures.
• Utilizing the MARS program for automated assignment in small proteins.
• Combining sequential connectivity information with RDC-matching for larger proteins.

Main Results:

• Over 90% backbone resonance assignment achieved for small proteins using MARS without sequential data.
• RDC-matching combined with sequential information improves residue assignment reliability and robustness against missing data in larger proteins.
• Deviations in structure or dynamics from the reference 3D coordinates did not increase assignment error rates.

Conclusions:

• RDC-enhanced assignment significantly improves the efficiency and reliability of protein backbone resonance assignment in NMR.
• This method is particularly valuable when traditional NMR assignment strategies yield limited reliable data.
• The approach is robust to structural or dynamic variations from the input 3D model coordinates.