title: Transcriptional regulation and posttranslational activity of the betaine transporter BetL in Listeria monocytogenes are controlled by environmental salinity.
abstract: While the genetic elements contributing to the salinity tolerance of Listeria monocytogenes have been well characterized, the regulatory signals and responses (genetic and/or biochemical) that govern these mechanisms have yet to be elucidated. Encoded by betL, the first genetic element to be linked to listerial osmotolerance, the secondary betaine uptake system BetL is a member of the betaine-carnitine-choline transporter family. Preceded by consensus sigma(A)- and sigma(B)-dependent promoter sites, betL is constitutively expressed and transcriptionally up-regulated in response to salt stress. The nisin-controlled expression system was used to achieve salinity-independent, controlled betL expression in Listeria. In the absence of NaCl-activated transcriptional control, BetL activity was found to be a function of environmental salinity, showing optimal activity in buffer supplemented with 1 to 2% NaCl (osmolality, 417 to 719 mosmol/kg). In addition, BetL was activated rapidly (half-life, 2 min) in response to an osmotic upshift imposed by adding 2% NaCl to 50 mM potassium phosphate buffer.
authors.affiliation: Department of Microbiology and Alimentary Pharmabiotic Centre, University College, Cork, Ireland.
authors.forename: Roy D
authors.initials: RD
authors.lastname: Sleator
authors.forename: Janet M
authors.initials: JM
authors.lastname: Wood
authors.forename: Colin
authors.initials: C
authors.lastname: Hill
mesh_terms: D001426:Bacterial Proteins; D001622:Betaine / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D004777:Environment; D015964:Gene Expression Regulation, Bacterial; D007700:Kinetics; D008089:Listeria monocytogenes / Q000235:genetics* / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D012965:Sodium Chloride / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: D001426:Bacterial Proteins; C119698:BetL protein, Listeria monocytogenes; D002352:Carrier Proteins; D001622:Betaine; D012965:Sodium Chloride