Structural heterogeneity in microcrystalline ubiquitin studied by solid-state NMR.

Area of Science:

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

Background:

• Solid-state NMR (ssNMR) is crucial for determining protein structures.
• Spectral crowding and limited resolution often hinder ssNMR analysis.
• Understanding protein conformational heterogeneity is vital for biological function.

Purpose of the Study:

• To improve spectral resolution and facilitate resonance assignment in ssNMR of ubiquitin.
• To obtain a high-precision ssNMR structure of microcrystalline ubiquitin.
• To investigate and characterize structural heterogeneity and conformational polymorphism in ubiquitin.

Main Methods:

• Application of [1-(13)C]- and [2-(13)C]-glucose labeling schemes to ubiquitin.
• Acquisition and analysis of solid-state NMR spectra.
• Calculation of a high-precision ssNMR protein structure.

Main Results:

• Significant reduction in spectral crowding and enhanced spectral resolution were achieved.
• Straightforward spectral resonance assignment and collection of long-range distance information were enabled.
• A high-precision ssNMR structure was determined, revealing three distinct conformations and structural heterogeneity in specific regions.

Conclusions:

• Isotopic labeling strategies effectively overcome ssNMR spectral crowding challenges.
• The study provides a high-resolution structure of ubiquitin, highlighting conformational heterogeneity.
• Observed structural polymorphism in ssNMR correlates with dynamic regions identified in solution NMR studies.