Interactions of the Fatty Acid-Binding Protein ReP1-NCXSQ with Lipid Membranes. Influence of the Membrane Electric Field on Binding and Orientation.

VANESA V. GALASSI; MARCOS A. VILLARREAL; VELIA POSADA; GUILLERMO G. MONTICH

BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2014 vol. 1838 p. 910 - 920

0005-2736

Rep1-NCXSQ is a 15 kDa soluble, intracellular protein that regulates the activity of the Na+/Ca+2 exchanger in the squid axon. It is a member of the CRABP family and the FABP superfamily. It is composed of ten beta strands defining an inner cavity and a domain of two short alpha helix segments. It is composed of ten beta strands defining an inner cavity and a domain of two short alpha helix segments. In this work, we studied the binding and orientation of ReP1-NCXSQ in anionic and zwitterionic lipid membranes using molecular dynamics (MD) simulations. Binding to lipids membranes was also measured by filtration binding assay. Rep1-NCXSQ acquired an orientation in the anionic membranes with the positive end of the macrodipole pointing to the lipid membrane. Potential of mean force calculations, in agreement with experimental measurements, showed that the binding to the anionic interfaces in low ionic strenght was stronger than the binding to anionic interfaces in high ionic strength or to zwitterionic membranes. The results of MD showed that the electrostatic binding can be mediated not only by defined patches or domains of basic residues but also by a global asymmetric distribution of charges. A combination of dipole-electric field interaction and local interactions determined the orientation of Rep1-NCXSQ in the interface.