Download MendeleyCryo-EM, X-ray diffraction, and atomistic simulations reveal determinants for the formation of a supramolecular myelin-like proteolipid lattice.
Ruskamo, S., Krokengen, O.C., Kowal, J., Nieminen, T., Lehtimaki, M., Raasakka, A., Dandey, V.P., Vattulainen, I., Stahlberg, H., Kursula, P.(2020) J Biol Chem 295: 8692-8705
- PubMed: 32265298
- DOI: https://doi.org/10.1074/jbc.RA120.013087
- Primary Citation of Related Structures:
6STS, 6XU5, 6XU9, 6XUA, 6XUW, 6XVQ, 6XVR, 6XVS, 6XVY, 6XW9 - PubMed Abstract:
Myelin protein P2 is a peripheral membrane protein of the fatty acid-binding protein family that functions in the formation and maintenance of the peripheral nerve myelin sheath. Several P2 gene mutations cause human Charcot-Marie-Tooth neuropathy, but the mature myelin sheath assembly mechanism is unclear. Here, cryo-EM of myelin-like proteolipid multilayers revealed an ordered three-dimensional (3D) lattice of P2 molecules between stacked lipid bilayers, visualizing supramolecular assembly at the myelin major dense line. The data disclosed that a single P2 layer is inserted between two bilayers in a tight intermembrane space of ∼3 nm, implying direct interactions between P2 and two membrane surfaces. X-ray diffraction from P2-stacked bicelle multilayers revealed lateral protein organization, and surface mutagenesis of P2 coupled with structure-function experiments revealed a role for both the portal region of P2 and its opposite face in membrane interactions. Atomistic molecular dynamics simulations of P2 on model membrane surfaces suggested that Arg-88 is critical for P2-membrane interactions, in addition to the helical lid domain. Negatively charged lipid headgroups stably anchored P2 on the myelin-like bilayer surface. Membrane binding may be accompanied by opening of the P2 β-barrel structure and ligand exchange with the apposing bilayer. Our results provide an unprecedented view into an ordered, multilayered biomolecular membrane system induced by the presence of a peripheral membrane protein from human myelin. This is an important step toward deciphering the 3D assembly of a mature myelin sheath at the molecular level.
Organizational Affiliation:
Faculty of Biochemistry and Molecular Medicine, University of Oulu, 90014 Oulu, Finland; Biocenter Oulu, University of Oulu, 90014 Oulu, Finland.
