A refined solution structure of hen lysozyme determined using residual dipolar coupling data.

Area of Science:

• Structural Biology
• Biophysics
• Nuclear Magnetic Resonance (NMR) Spectroscopy

Background:

• Determining high-resolution protein structures in solution is crucial for understanding biological function.
• Nuclear magnetic resonance (NMR) spectroscopy is a powerful technique for structural biology.
• Residual dipolar couplings (RDCs) provide long-range orientational information, enhancing structure determination.

Purpose of the Study:

• To determine a high-resolution NMR structure of hen lysozyme.
• To evaluate the contribution of RDC restraints to the accuracy of NMR structures.
• To investigate the solution structure and dynamics of hen lysozyme.

Main Methods:

• High-resolution NMR structure determination using a combination of NOE distance restraints, torsion angle restraints, hydrogen bond restraints, and residual 1H-15N dipolar coupling restraints.
• Measurements of RDCs were performed in two different dilute liquid crystalline phases (bicelles).
• Comparison of structures calculated with and without RDC data to assess the impact of RDCs.

Main Results:

• An ensemble of 50 low-energy NMR structures of hen lysozyme was generated with good agreement to the mean structure and crystal structure.
• Structures calculated with RDC data showed improved similarity to the crystal structure and better stereochemical quality compared to those without RDCs.
• The NMR structures demonstrated improved quality factors when validated against independent RDC and relaxation data.

Conclusions:

• Residual dipolar couplings significantly enhance the accuracy and quality of NMR-derived protein structures.
• The determined NMR structure provides a detailed description of hen lysozyme in solution.
• Analysis of the structures offers insights into the dynamical behavior of hen lysozyme.