Cooperation of Helix Insertion and Lateral Pressure to Remodel Membranes.

Nature has developed different protein mediated mechanisms to remodel cellular membranes. One of the proteins that is implicated in these processes is alpha-synuclein (alpha S). Here we investigate if besides alpha S's membrane bound amphipathic helix the disordered, solvent exposed tail of the protein contributes to membrane reshaping. We produced alpha S variants with elongated or truncated disordered solvent exposed domains. We observe a transformation of opaque multi lamellar vesicle solutions into nonscattering solutions containing smaller structures upon addition of all alpha S variants. Experimental data combined with model calculations show that the cooperation of helix insertion and lateral pressure exerted by the disordered domain makes the full length protein decidedly more efficient in membrane remodeling than the truncated version. Using disordered domains may not only be cost-efficient, it may also add a new level of control over vesicle fusion/fission by expansion or compaction of the domain.