Defining the interacting regions between apomyoglobin and lipid membrane by hydrogen/deuterium exchange coupled to...

Area of Science:

• Biochemistry
• Structural Biology
• Membrane Biophysics

Background:

• Sperm whale apomyoglobin serves as a model protein for the globin family.
• Interactions of apomyoglobin with lipid bilayers show similarities to bacterial toxin pore-forming domains.
• Understanding protein-lipid interactions is crucial for membrane protein function and drug development.

Purpose of the Study:

• To characterize the different states of apomyoglobin bound to lipid bilayers.
• To investigate the pH-dependence of apomyoglobin's interaction with membranes.
• To explore the potential of hydrogen/deuterium exchange mass spectrometry for studying membrane-bound proteins.

Main Methods:

• Utilized hydrogen/deuterium exchange experiments coupled with mass spectrometry.
• Analyzed apomyoglobin's structural changes upon binding to lipid bilayers at varying pH.
• Focused on identifying specific protein regions involved in membrane interactions.

Main Results:

• At pH 5.5, apomyoglobin binds to lipid bilayers in a native-like state, primarily interacting via alpha-helix A.
• At pH 4, apomyoglobin adopts a partially folded state, with alpha-helices A and G involved in membrane interaction.
• Alpha-helix G, a hydrophobic region, becomes accessible for lipid bilayer interaction at pH 4 due to tertiary structure loss.

Conclusions:

• Apomyoglobin exhibits distinct pH-dependent conformational changes upon membrane binding.
• Hydrogen/deuterium exchange mass spectrometry is a feasible method for characterizing membrane-bound protein states.
• This technique holds potential for studying partially folded amphitropic proteins interacting with membranes, which is challenging for other high-resolution methods.