Reconstituted P2/Myelin‐Lipid Multilayers

Abstract

A complex forms when bovine P2 protein is added to single-bilayer vesicles created by sonicating myelin lipids. The complex was studied by biochemical analysis, freeze-fracture (FF) and thin-section electron microscopy (EM), and by X-ray diffraction. Smaller amounts of P2 cause the vesicles to aggregate and fuse whereas larger amounts (greater than or equal to 4 wt%) cause multilayers to form. Binding saturates at 15 wt% P2. FF EM shows that large, flat multilayers form within 15 min of addition of P2. Only smooth fracture faces are seen, as expected for a peripheral membrane protein. X-ray diffraction shows a constant repeating distance in the multilayers: 86.0 +/- 0.7 A between the centers of bilayers in the range 4 wt% less than or equal to P2/(P2 + lipid) less than or equal to 15 wt%. Assuming a 53 A-thick bilayer, the space between bilayers is 33 A wide. This is a wider space than for myelin basic protein (MBP) (20-25 A wide). The respective widths are consistent with a compact, globular structure for P2 and a flattened shape for MBP. Calculated electron-density profiles of the lipids with and without P2 reveal the protein largely in the interbilayer spaces, with a small part possibly inserted into the lipid headgroup layers. The different proportions of P2 in the sciatic nerve of various species are tentatively correlated with the different average widths observed by X-ray diffraction for the cytoplasmic space (major period line) between bilayers in the respective sciatic myelins.

A role of peripheral myelin protein 2 in lipid homeostasis of myelinating schwann cells

“…stacking (Sedzik et al, 1985;Suresh et al, 2010). Further studies are, therefore, needed to clarify the biological significance of this interaction.…”

High-resolution structural model of porcine P2 myelin membrane protein with associated fatty acid ligand: Fact or artifact?

“…Per one molecule of P2, on average there is one molecule of MBP. Reconstitution of myelin membrane with lipid and P2 protein uncovered that the diameter of P2 protein is approximately 35 Å (Sedzik et al, 1985), and P2 protein may penetrate as deeply as 5 Å into the bilayer lipid head groups. Such ''cavities'' can be formed because of clustering of cholesterol (Sedzik et al, 1985).…”

“…Reconstitution of myelin membrane with lipid and P2 protein uncovered that the diameter of P2 protein is approximately 35 Å (Sedzik et al, 1985), and P2 protein may penetrate as deeply as 5 Å into the bilayer lipid head groups. Such ''cavities'' can be formed because of clustering of cholesterol (Sedzik et al, 1985). Taking into consideration that phosphorylation sites are never phosphorylated in P2 protein, this may indicate that these sites are not accessible for serine and tyrosine kinesis enzyme.…”

“…P2 is localized in compact myelin; therefore, it is obvious to suspect that P2 must interact with all myelin lipids, including cholesterol. It is also known that P2 protein forms multilayered structures with myelin lipid vesicles (Sedzik et al, 1985).…”

Myelin-derived and putative molecular mimic peptides share structural properties in aqueous and membrane-like environments

“…It is a proposed target of autoimmune reactions in GBS, and P2 peptides can be used to induce EAN, the mouse model of human GBS [74,75]. P2 is able to stack lipid bilayers together in an ordered manner in vitro [41,76,77], and the P2 knockout mouse has changes in myelin lipid composition and motor nerve conduction velocity during periods of active myelination [73].…”