title: Osmoprotection by carnitine in a Listeria monocytogenes mutant lacking the OpuC transporter: evidence for a low affinity carnitine uptake system.
abstract: A deletion mutant of Listeria monocytogenes lacking OpuC, an ABC transporter responsible for the uptake of the compatible solute carnitine, was constructed and carnitine transport assays confirmed that carnitine transport was defective in this mutant. However, the mutant retained the ability to derive osmoprotection from carnitine, suggesting the presence of a second uptake system for this compatible solute. Measurement of intracellular carnitine pools during balanced growth confirmed that the opuC mutant accumulated high levels of carnitine. These pools were only achieved in the mutant when high levels (1 mM) of carnitine were present extracellularly. When a lower level (100 microM) was supplied in the medium the mutant failed to accumulate a substantial intracellular pool and failed to derive osmoprotection from carnitine. These data suggest the presence of a second low affinity carnitine uptake system in this osmotolerant pathogen.
authors.affiliation: Department of Molecular and Cell Biology, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK.
authors.forename: Katy R
authors.initials: KR
authors.lastname: Fraser
authors.forename: Conor P
authors.initials: CP
authors.lastname: O'Byrne
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D001426:Bacterial Proteins; D001692:Biological Transport; D002331:Carnitine / Q000378:metabolism* / Q000502:physiology*; D019610:Cytoprotection; D017353:Gene Deletion; D008089:Listeria monocytogenes / Q000235:genetics / Q000378:metabolism*; D009995:Osmosis
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; C119750:OpuC protein, bacteria; D002331:Carnitine