Interaction of a Peripheral Acidic Protein with Anionic Lipid Membranes: Insights from Molecular Dynamics

VANESA V. GALASSI; MARCOS A. VILLARREAL; LUIS BEAUGE; MARIANA BOLLO; GRACIELA BERBERIAN; GUILLERMO G. MONTICH

San Diego

Congreso; 56th Annual Meeting of the Biophysical Society; 2012

Biophysical Society

The fatty acid-binding protein ReP1 is a soluble protein that shows the common beta-barrel motif with two alpha-helix in the portal region. Its isoelectric point of 5.85 leads to net charge of −1 at neutral pH. Previous evidence of its interaction with anionic lipids [1], makes it an attractive model to test the hypothesis that the binding and orientation of soluble proteins within lipid membranes are driven by the interaction of its macrodipole with the interphasial electric field [2].The interaction of ReP1 with lipid membranes of anionic and zwitterionic phospholipids was studied by multiple-run molecular dynamics, Potential of Mean Force calculations and filtration assays. ReP1 has a macrodipole of 310 Debyes pointing towards the portal region. We found that it interacted selectively with anionic interphases, aligning its macrodipole in the configuration of lowest energy within the membrane electric field. Additional evidence of this orientation was achieved experimentally by FRET measurements. This orientation led to the portal region in contact with the membrane. The strength and range of the interaction and the preference in spacial configuration was attenuated by the presence of salt. A global loss of compactness was seen by MD and FT-IR spectroscopy.A similar behaviour has been described for L-BABP [2], a protein with identical tertiary structure.These electrostatic-like features of the interaction suggest that the interphasial electric field could be the driving force for the binding and orientation, and may be involved on the ligand delivery mechanism in this family of proteins.[1] Berberián G., Bollo M., Montich G., Roberts G., DeGiorgis JA., DiPolo R., Beaugé L., Biochimica et Biophysica Acta, 1788, 1255-1262 (2009).[2] Villarreal MA., Perduca M., Monaco HL., Montich GG., Biochimica et Biophysica Acta, 1778, 1390-1397 (2008).