Investigation of Lipid Transfer between Model Membranes and the Effect of a Transport Protein on Trafficking

The phospholipid composition of biological membranes is precisely controlled, and slight tuning of lipid content can have drastic effects on macroscopic membrane properties and the critically important functions of membrane-associated proteins. Both spontaneous and protein-catalyzed exchange of lipids between membranes are mechanisms for modulating membrane lipid composition. Here, an <i>in vitro</i> platform for the analysis of the transfer of tagged lipid derivatives between synthetic liposomes is developed and used to systematically investigate the effect of bulk solution properties, such as temperature, pH, and liposome concentration, on the exchange of lipids between model membranes. The impact of a representative lipid transport protein was studied to understand the role of protein concentration and membrane anchoring on lipid exchange. The spontaneous exchange of lipids between model membranes is enhanced by the addition of the model transport protein when protein-membrane interactions are mediated through anchoring. These data suggest that membrane-binding proteins may play an integral role in catalyzing the transfer of lipids between membranes.