Multidimensional oriented solid-state NMR experiments enable the sequential assignment of uniformly 15N labeled...

Area of Science:

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

Background:

• Oriented solid-state NMR is crucial for determining membrane protein orientation relative to lipid bilayers.
• Current methods rely on measuring (1)H-(15)N dipolar couplings (DC) and (15)N anisotropic chemical shifts (CSA).
• A key limitation is the lack of effective experiments for sequential assignment of amide resonances.

Purpose of the Study:

• To develop a new pulse sequence for complete and unambiguous assignment of (15)N resonances in membrane proteins.
• To overcome the limitations of existing NMR techniques for membrane protein structural analysis.

Main Methods:

• A novel 3D experiment, [(1)H,(15)N]-SE-PISEMA-PDSD, integrating proton driven spin diffusion (PDSD) with sensitivity-enhanced PISEMA.
• Inclusion of 2D (15)N/(15)N spin diffusion experiments within the 3D sequence.
• Demonstration using the membrane protein sarcolipin reconstituted in magnetically aligned lipid bicelles.

Main Results:

• The new 3D NMR experiment enables complete and unambiguous assignment of (15)N resonances.
• The method was successfully demonstrated on sarcolipin, a membrane protein.
• This technique facilitates the determination of sequential assignments for integral membrane proteins.

Conclusions:

• The developed [(1)H,(15)N]-SE-PISEMA-PDSD pulse sequence significantly advances membrane protein NMR analysis.
• This approach, combined with low electric field probe technology, will accelerate structural and topological determination of large integral membrane proteins.
• It provides a powerful tool for understanding membrane protein function and dynamics in their native-like environments.