Orientation Determination of Membrane-Disruptive Proteins Using Powder Samples and Rotational Diffusion: A Simple...

Area of Science:

• Biophysics
• Structural Biology
• Membrane Protein Dynamics

Background:

• Determining the orientation of membrane proteins is crucial for understanding their function.
• Traditional methods often require macroscopic alignment, which is not feasible for all proteins.
• Fast uniaxial rotation around the bilayer normal presents a challenge for orientation determination.

Purpose of the Study:

• To develop a method for determining membrane protein orientation without macroscopic alignment.
• To analyze the orientation of a beta-sheet antimicrobial peptide using this new approach.
• To enable orientation determination for membrane-disruptive proteins in various settings.

Main Methods:

• Utilizing motionally averaged powder spectra from fast uniaxial rotation.
• Exploiting the equivalence between powder spectra 0° frequency and aligned sample peak position.
• Applying (13)CO and (15)N chemical shifts from powder spectra for orientation determination.
• Employing magic-angle spinning for enhanced spectral resolution.

Main Results:

• Demonstrated that motionally averaged powder spectra's 0° frequency matches the peak of an aligned sample.
• Successfully determined the orientation of a beta-sheet antimicrobial peptide not amenable to macroscopic alignment.
• Validated the powder sample approach for orientation determination.

Conclusions:

• The developed method allows for orientation determination of membrane proteins without macroscopic alignment.
• This technique is applicable to proteins that are naturally membrane-disruptive and difficult to align.
• The approach is versatile, working in diverse environments and under magic-angle spinning conditions.