title: Electrostatic interactions drive the nonsteric directional block of OmpF channel by La3+.
abstract: Ion channels regulate the transport of molecules and the electric signal transduction in living cells by means of complex and even highly sophisticated mechanisms. We focus here on the crucial role that polyvalent ions, well-known modulators of many biological nanosystems, play in ion channel function. In particular, we show that trace amounts of lanthanum are able to block the bacterial porin OmpF, a large biological pore of Escherichia coli wide enough to exchange antibiotics and other larger molecules. The underlying mechanism has a strong directional character: it is sensitive to the sign of the applied voltage and to the side of the blocker addition. We explore these channel features by combining planar lipid bilayer electrophysiology at the single channel level, site-directed mutagenesis, and inductively coupled plasma mass spectrometry (ICP-MS). In contrast to other well-described channel blockers, which seem to occlude the narrower part of the pore, we envisage a nonsteric mechanism based on electrostatic interactions.
authors.affiliation: Laboratory of Molecular Biophysics, Department of Physics, Universitat Jaume I , 12071 Castellón, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Queralt-Martín
authors.forename: Carmina
authors.initials: C
authors.lastname: Verdiá-Báguena
authors.forename: Vicente M
authors.initials: VM
authors.lastname: Aguilella
authors.forename: Antonio
authors.initials: A
authors.lastname: Alcaraz
mesh_terms: D007811:Lanthanum / Q000494:pharmacology*; D013058:Mass Spectrometry; D018272:Porins / Q000737:chemistry* / Q000187:drug effects*; D055672:Static Electricity
chemical_list: C109237:OmpF protein; D018272:Porins; D007811:Lanthanum