Proton clouds to measure long-range contacts between nonexchangeable side chain protons in solid-state NMR

Area of Science:

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

Background:

• Studying protein tertiary structure is crucial for understanding biological function.
• Proton-detected solid-state NMR is a powerful technique for this purpose.
• Challenges remain in achieving high spectral resolution for complex protein systems.

Purpose of the Study:

• To develop a novel labeling strategy for enhanced protein structure determination using solid-state NMR.
• To improve spectral resolution and access long-range structural information in proteins.
• To demonstrate the broad applicability of the new method across different protein types.

Main Methods:

• Selective labeling of proteins with protonated amino acids in a perdeuterated matrix ('proton clouds').
• Utilizing proton-detected solid-state NMR spectroscopy.
• Applying the method to ubiquitin and the β-barrel membrane protein BamA.

Main Results:

• Achieved general access to long-range contacts between nonexchangeable side chain protons.
• Significantly improved spectral resolution by reducing proton line width and spectral crowding.
• Demonstrated the method's effectiveness on both a small globular protein (ubiquitin) and a membrane protein (BamA).

Conclusions:

• Proton-cloud labeling is a versatile and effective strategy for solid-state NMR studies of protein structure.
• The technique overcomes limitations in spectral resolution and crowding, enabling detailed structural analysis.
• This approach facilitates the study of protein tertiary structure, including challenging membrane proteins.