Myelin basic protein binding is modulated by leaflet asymmetry and lipid composition

Compositional asymmetry between lipid bilayer leaflets is a defining feature of biological membranes and can modulate protein binding. Here, we investigate how leaflet-specific composition affects the interaction between Myelin Basic Protein and biomimetic myelin membranes using neutron reflectometry. Asymmetric supported myelin bilayers containing deuterated cholesterol in the cytoplasmic leaflet enabled resolution of structural asymmetry. Neutron reflectometry measurements show that Myelin Basic Protein binds preferentially to asymmetric supported bilayers mimicking native myelin, whereas Experimental Autoimmune Encephalomyelitis-modified compositions exhibit weaker binding and more pronounced protein insertion. Disruption of asymmetry-either by thermally induced lipid redistribution or by using symmetric cytoplasmic myelin-leads to a marked reduction in Myelin Basic Protein binding, despite increased membrane charge. Following vesicle adsorption and formation of a second bilayer, the protein layer narrows to near in vivo thickness in both systems, with the diseased condition exhibiting a wider inter-bilayer spacing. These results underscore the relevance of lipid asymmetry and composition in governing protein-membrane interactions, with implications for the molecular basis of myelin stability and demyelination.