Rearrangement of lipid ordered phases upon protein adsorption due to multiple site binding

Area of Science:

• Biophysics
• Surface Chemistry
• Protein-Lipid Interactions

Background:

• Proteins interact with lipid membranes, influencing membrane structure and function.
• Metal ions play a crucial role in mediating protein-lipid interactions.
• Langmuir monolayers provide a model system to study these interactions at an air-water interface.

Purpose of the Study:

• To investigate the structural rearrangement of metal-chelating lipid monolayers upon protein adsorption.
• To compare the effects of proteins with varying numbers of histidine residues on lipid monolayer structure.
• To understand the role of binding site multiplicity and binding energy in protein-induced lipid rearrangement.

Main Methods:

• Formation of Langmuir monolayers using a metal-chelating lipid.
• Loading of divalent metal ions into the lipid headgroups.
• Adsorption of proteins (myoglobin, synthetic peptide, lysozyme) onto the monolayer.
• Analysis of lipid film structural rearrangement using surface pressure and potentially other techniques.

Main Results:

• Protein adsorption is driven by specific interactions between histidine residues and metal ions.
• Proteins with multiple histidines induced significant structural rearrangement of the lipid monolayer.
• Proteins with a single histidine showed less pronounced rearrangement.
• The kinetics and nature of lipid rearrangement were dependent on binding energy and initial film pressure.

Conclusions:

• The multiplicity of histidine binding sites on a protein significantly influences the extent of lipid monolayer rearrangement.
• Protein-lipid interactions at interfaces are governed by specific binding events and the available binding sites.
• Lipid film pressure and binding energy are critical factors modulating the dynamics of protein-induced structural changes.