Dynamics of the Peripheral Membrane Protein P2 from Human Myelin Measured by Neutron Scattering—A Comparison between Wild-Type Protein and a Hinge Mutant

Abstract

Myelin protein P2 is a fatty acid-binding structural component of the myelin sheath in the peripheral nervous system, and its function is related to its membrane binding capacity. Here, the link between P2 protein dynamics and structure and function was studied using elastic incoherent neutron scattering (EINS). The P38G mutation, at the hinge between the β barrel and the α-helical lid, increased the lipid stacking capacity of human P2 in vitro, and the mutated protein was also functional in cultured cells. The P38G mutation did not change the overall structure of the protein. For a deeper insight into P2 structure-function relationships, information on protein dynamics in the 10 ps to 1 ns time scale was obtained using EINS. Values of mean square displacements mainly from protein H atoms were extracted for wild-type P2 and the P38G mutant and compared. Our results show that at physiological temperatures, the P38G mutant is more dynamic than the wild-type P2 protein, especially on a slow 1-ns time scale. Molecular dynamics simulations confirmed the enhanced dynamics of the mutant variant, especially within the portal region in the presence of bound fatty acid. The increased softness of the hinge mutant of human myelin P2 protein is likely related to an enhanced flexibility of the portal region of this fatty acid-binding protein, as well as to its interactions with the lipid bilayer surface requiring conformational adaptations.

Determinants for forming a supramolecular myelin-like proteolipid lattice

“…Neither the bilayer spacing nor protein-lipid organization altered in the presence of the mutant. During sample preparation, P38G induced membrane aggregation/stacking faster than wtP2, and the turbidity effect was visible within 2-3 min (not shown), in line with earlier experiments 46 .…”

“…Cryo-EM was similarly carried out with the “hyperactive” P38G variant 46 mixed with lipids (Figure 1E). Neither the bilayer spacing nor protein-lipid organization altered in the presence of the mutant.…”

“…Structures of wtP2 and P38G were prepared for the simulations essentially as described elsewhere 46 . Briefly, the P2 structure with bound palmitate was taken from the PDB entry 4BVM 15 and converted to match an all-atom representation consistent with the CHARMM36 force field 47 , which was used for simulating the system components, unless mentioned otherwise.…”

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

“…a The GBS epitope corresponds to the first α helix in the P2 crystal structure [44]. The two helices form a lid, proposed to interact with the myelin membrane and possibly open upon ligand entry and release [79]. b DPC titration.…”

“…7a). It is likely that the helical lid is centrally involved in membrane interactions during membrane stacking [79].…”