Measuring transmembrane helix interaction strengths in lipid bilayers using steric trapping

Area of Science:

• Biochemistry
• Structural Biology
• Membrane Biophysics

Background:

• Transmembrane (TM) helix interactions are crucial for membrane protein function.
• Measuring strong TM helix interaction affinities in lipid bilayers is challenging with traditional methods.

Purpose of the Study:

• To develop a novel method for quantifying strong TM helix interaction affinities in lipid bilayers.
• To extend the measurable range of dissociation constants for TM helix dimers.

Main Methods:

• Developed a technique called steric trapping.
• Steric trapping utilizes biotinylated TM helices and competitive binding with monovalent streptavidin (mSA).
• Adjustable mSA binding affinity allows for a wide range of dissociation constant measurements.

Main Results:

• Steric trapping enables measurement of TM helix dimer dissociation constants (K d,dimer) over six orders of magnitude.
• The method extends the lower limit of measurable K d,dimer by 3-4 orders of magnitude compared to dilution methods.
• Detailed protocols for applying steric trapping to TM helix dimers are provided.

Conclusions:

• Steric trapping offers a powerful new approach for studying TM helix interactions in native-like lipid bilayer environments.
• This method facilitates research into the folding and assembly of α-helical membrane proteins.
• Opens new avenues for investigating membrane protein dynamics and interactions.