title: Role of the central arginine R133 toward the ion selectivity of the phosphate specific channel OprP: effects of charge and solvation.
abstract: The outer membrane porin OprP of Pseudomonas aeruginosa forms a highly specific phosphate selective channel. This channel is responsible for the high-affinity uptake of phosphate ions into the periplasmic space of the bacteria. A detailed investigation of the structure-function relationship of OprP is inevitable to decipher the anion and phosphate selectivity of this porin in particular and to broaden the present understanding of the ion selectivity of different channels. To this end we investigated the role of the central arginine of OprP, R133, in terms of its effects in selectivity and ion transport properties of the pore. Electrophysiological bilayer measurements and free-energy molecular dynamics simulations were carried out to probe the transport of different ions through various R133 mutants. For these mutants, the change in phosphate binding specificity, ion conduction, and anion selectivity was determined and compared to previous molecular dynamic calculations and electrophysiological measurements with wild-type OprP. Molecular analysis revealed a rather particular role of arginine 133 and its charge, while at the same time this residue together with the network of other residues, namely, D94 and Y114, has the ability to dehydrate the permeating ion. These very specific features govern the ion selectivity of OprP.
authors.affiliation: School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany.
authors.forename: Niraj
authors.initials: N
authors.lastname: Modi
authors.forename: Iván
authors.initials: I
authors.lastname: Bárcena-Uribarri
authors.forename: Manjeet
authors.initials: M
authors.lastname: Bains
authors.forename: Roland
authors.initials: R
authors.lastname: Benz
authors.forename: Robert E W
authors.initials: RE
authors.lastname: Hancock
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kleinekathöfer
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites / Q000235:genetics; D001667:Binding, Competitive; D015640:Ion Channel Gating / Q000235:genetics / Q000502:physiology; D017136:Ion Transport / Q000235:genetics / Q000502:physiology; D008051:Lipid Bilayers / Q000737:chemistry; D008564:Membrane Potentials / Q000235:genetics / Q000502:physiology; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D009154:Mutation; D010710:Phosphates / Q000737:chemistry / Q000378:metabolism*; D018272:Porins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D012996:Solutions / Q000737:chemistry
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D008051:Lipid Bilayers; D010710:Phosphates; D018272:Porins; D012996:Solutions; C065416:oprP protein, Pseudomonas aeruginosa; D001120:Arginine