Mechanistic Insights into Microsecond Time-Scale Motion of Solid Proteins Using Complementary ¹⁵N and ¹H Relaxation...

Area of Science:

• Biophysical Chemistry
• Structural Biology
• Protein Dynamics

Background:

• Protein dynamics on the microsecond timescale are crucial for function but challenging to study.
• NMR relaxation dispersion is a powerful technique for observing these motions in proteins.
• Complementary information can be obtained using different nuclei and relaxation dispersion methods.

Purpose of the Study:

• To demonstrate the utility of combining various solution- and solid-state NMR relaxation dispersion methods.
• To investigate microsecond timescale protein backbone motion in the alpha-spectrin SH3 domain.
• To elucidate the conformational dynamics of the ligand recognition loop and their functional implications.

Main Methods:

• Application of multiple solution-state NMR relaxation dispersion techniques (e.g., Bloch-McConnell, near-rotary-resonance).
• Utilized solid-state NMR relaxation dispersion methods for comparison and complementary data.
• Studied microcrystalline alpha-spectrin SH3 domain to model conformational rearrangements.

Main Results:

• Identified and modeled functionally relevant conformational rearrangements of the ligand recognition loop on microsecond timescales.
• Observed protein dynamics in both solution and crystalline states, highlighting inherent plasticity.
• The SH3 domain exists in a dynamic equilibrium between binding-competent and ground-state conformations.

Conclusions:

• Combined NMR relaxation dispersion methods provide comprehensive insights into protein conformational dynamics.
• The observed plasticity of the SH3 domain is consistent with a conformational-preselection binding model.
• These findings offer new perspectives on the recognition mechanisms of SH3 domains.