Depth of ?-synuclein in a bilayer determined by fluorescence, neutron reflectometry, and computation.

ABSTRACT: ?-Synuclein (?-syn) membrane interactions are implicated in the pathogenesis of Parkinson's disease. Fluorescence and neutron reflectometry (NR) measurements reveal that ?-syn penetrates ?9-14 Å into the outer leaflet of the bilayer, with a substantial portion of the membrane-bound polypeptide extending into the aqueous solvent. For the first time, to our knowledge, we used NR to obtain direct quantitative evidence of ?-syn-induced membrane thinning. To examine the effect of specific residues on membrane penetration depths, we used a series of W4-containing N-terminal peptides. We identified that the first 15 residues (P15) nearly recapitulate the features of the full-length protein (i.e., partition constants, molecular mobility, and insertion of the W4 side chain into the bilayer), and found that as few as the first four N-terminal residues are sufficient for vesicle binding. Although at least one imperfect amphipathic repeat sequence (KAKEGV) is required for ?-helical formation, secondary structural formation has little effect on membrane affinity. To develop an N-terminal ?-syn model for bilayer interactions, we performed molecular-dynamics simulations of the P15 peptide submerged in a bilayer. The simulation results are highly consistent with experimental data indicating a broad low-energy region (8.5-14.5 Å) for W4 insertion.

SUBMITTER: Pfefferkorn CM 

PROVIDER: S-EPMC3274814 | biostudies-other | 2012 Feb

REPOSITORIES: biostudies-other