title: Characterization of OpdH, a Pseudomonas aeruginosa porin involved in the uptake of tricarboxylates.
abstract: The Pseudomonas aeruginosa outer membrane is intrinsically impermeable to many classes of antibiotics, due in part to its relative lack of general uptake pathways. Instead, this organism relies on a large number of substrate-specific uptake porins. Included in this group are the 19 members of the OprD family, which are involved in the uptake of a diverse array of metabolites. One of these porins, OpdH, has been implicated in the uptake of cis-aconitate. Here we demonstrate that this porin may also enable P. aeruginosa to take up other tricarboxylates. Isocitrate and citrate strongly and specifically induced the opdH gene via a mechanism involving derepression by the putative two-component regulatory system PA0756-PA0757. Planar bilayer analysis of purified OpdH demonstrated that it was a channel-forming protein with a large single-channel conductance (230 pS in 1 M KCl; 10-fold higher than that of OprD); however, we were unable to demonstrate the presence of a tricarboxylate binding site within the channel. Thus, these data suggest that the requirement for OpdH for efficient growth on tricarboxylates was likely due to the specific expression of this large-channel porin under particular growth conditions.
authors.affiliation: Department of Microbiology and Immunology, University of British Columbia, #235 2259 Lower Mall, Lower Mall Research Station, Vancouver, British Columbia, V6T 1Z4 Canada.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Tamber
authors.forename: Elke
authors.initials: E
authors.lastname: Maier
authors.forename: Roland
authors.initials: R
authors.lastname: Benz
authors.forename: Robert E W
authors.initials: RE
authors.lastname: Hancock
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D002412:Cations / Q000494:pharmacology; D019343:Citric Acid / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005816:Genetic Complementation Test; D016680:Genome, Bacterial; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009154:Mutation; D016133:Polymerase Chain Reaction; D018272:Porins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D014233:Tricarboxylic Acids / Q000737:chemistry / Q000493:pharmacokinetics* / Q000494:pharmacology
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002412:Cations; D018272:Porins; D014233:Tricarboxylic Acids; D019343:Citric Acid