Structural and dynamic analysis of residual dipolar coupling data for proteins.

Area of Science:

• Biophysics
• Structural Biology
• Protein NMR Spectroscopy

Background:

• Residual dipolar couplings (RDCs) in weakly aligned proteins provide valuable solution-state structural and dynamic information.
• Extracting distinct structural and dynamic properties from RDC measurements, which represent a convolution of both, is a significant challenge.

Purpose of the Study:

• To develop and present a formalism for the first-order separation of structural and dynamic effects in RDC data.
• To enable the simultaneous extraction of structural and motional parameters from RDC measurements.
• To introduce a generalized degree of order for discussing motion's impact on RDCs.

Main Methods:

• Development of a novel formalism for separating structural and dynamic contributions to RDCs.
• Introduction of a generalized degree of order parameter.
• Application of the methodology to (15)N,(13)C-labeled human ubiquitin in dilute bicelle solution.

Main Results:

• The proposed formalism allows for the simultaneous extraction of structural and motional parameters from RDC data.
• Ubiquitin's solution structure, derived from RDCs, aligns well with its known X-ray structure for the protein core.
• RDC data support a dynamic model for ubiquitin, indicating variable amplitudes and anisotropy in internal motions.

Conclusions:

• The developed methodology effectively separates structural and dynamic information from RDC measurements.
• Residual dipolar couplings can be primarily utilized for characterizing both the structure and anisotropic internal motions of proteins in solution.
• This approach enhances the understanding of protein dynamics and structure in their native-like solution state.