Role of Helix-0 of the N-BAR domain in membrane curvature generation
Fabio M. Fernandes 1, Luis M. S. Loura 2, Francisco J. Chichón 3, Jose L. Carrascosa 4, Alexander Fedorov 1 and Manuel Prieto 5*
1 Instituto Superior Técnico
2 Universidade de Coimbra
3 Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas
4 Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Cientícas
5 Instituto Superior Tecnico
* To whom correspondence should be addressed. E-mail: manuel.prieto{at}ist.utl.pt.
Submitted on May 21, 2007
Revised on July 8, 2007
Accepted on 26 November 2007
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Abstract |
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A group of proteins with cell membrane remodeling properties are also able to change dramatically the morphology of liposomes in vitro, frequently inducing tubulation. For a number of these proteins, the mechanism by which this effect is exerted has been proposed to be the embedding of amphipathic helices into the lipid bilayer. For proteins presenting BAR domains, removal of a N-terminal amphipathic alpha-helix (H0-NBAR) results in much lower membrane tubulation efficiency, pointing to a fundamental role of this protein segment. Here, we studied the interaction of a peptide corresponding to H0-NBAR with model lipid membranes. H0-NBAR bound avidly to anionic liposomes but partitioned weakly to zwitterionic bilayers, suggesting an essentially electrostatic interaction with the lipid bilayer. Interestingly, it is shown that after membrane incorporation, the peptide oligomerizes as an antiparallel dimer, suggesting a potential role of H0-NBAR in the mediation of BAR domain oligomerization. Through monitoring the effect of H0-NBAR on liposome shape by cryo-electron microscopy it is clear that membrane morphology is not radically changed. We conclude that H0-NBAR alone is not able to induce vesicle curvature, and its function must be related to the promotion of the scaffold effect provided by the concave surface of the BAR domain.
Key Words:
BAR proteins, FRET, amphipatic peptide, fluorescence, membrane tubulation
