title: Interactions of the fatty acid-binding protein ReP1-NCXSQ with lipid membranes. Influence of the membrane electric field on binding and orientation.
abstract: The regulatory protein of the squid nerve sodium calcium exchanger (ReP1-NCXSQ) is a 15kDa soluble, intracellular protein that regulates the activity of the Na(+)/Ca(2+) exchanger in the squid axon. It is a member of the cellular retinoic acid-binding proteins family and the fatty acid-binding proteins superfamily. 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 lipid 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 strength 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.
authors.affiliation: Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, X5000HUA, Córdoba, Argentina.
authors.forename: Vanesa V
authors.initials: VV
authors.lastname: Galassi
authors.affiliation: Instituto de Investigaciones en Físico-Química de Córdoba (INFIQC), CONICET, Departamento de Matemática y Física, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, X5000HUA, Córdoba, Argentina.
authors.forename: Marcos A
authors.initials: MA
authors.lastname: Villarreal
authors.affiliation: Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, X5000HUA, Córdoba, Argentina.
authors.forename: Velia
authors.initials: V
authors.lastname: Posada
authors.affiliation: Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, X5000HUA, Córdoba, Argentina. Electronic address: gmontich@fcq.unc.edu.ar.
authors.forename: Guillermo G
authors.initials: GG
authors.lastname: Montich
mesh_terms: D000818:Animals; D049832:Decapodiformes; D004560:Electricity; D050556:Fatty Acid-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D011487:Protein Conformation; D019831:Sodium-Calcium Exchanger / Q000737:chemistry / Q000378:metabolism*
chemical_list: D050556:Fatty Acid-Binding Proteins; D008051:Lipid Bilayers; D008563:Membrane Lipids; D019831:Sodium-Calcium Exchanger
keywords: 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine; 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol; Binding; CM; CRABP; FABP; HB; LUV; Lipid membrane; MD; Molecular dynamics; Orientation; PMF; POPC; POPG; ReP1-NCXSQ; cellular retinoic acid-binding protein; center of mass; fatty acid-binding protein; hydrogen bond; large unilamellar vesicle; molecular dynamics; potential of mean force; regulatory protein of the squid nerve sodium calcium exchanger