PDR12 encodes an ATP-binding cassette (ABC) transporter which is required for the development of weak organic acid resistance by mediating the energy-dependent extrusion of water-soluble carboxylate anions from the cell (5). Located in the plasma membrane, Pdr12p appears to confer resistance to those carboxylic acids that partition into both the lipid bilayer and aqueous phases (6), especially water-soluble, monocarboxylic acids with chain lengths of from C(1) to C(7) (2).

PDR12 is strongly induced by sorbate, benzoate and certain other moderately lipophilic carboxylate compounds, but not by organic alcohols or high levels of acetate (6). The PDR12 promoter contains a cis-acting weak acid response element (WARE) which is required for its induction (7). This WARE is the major target of transcription factor War1p under sorbic acid stress (4). War1p occupies the site in the both presence and absence of stress, demonstrating constitutive DNA binding, and suggesting that weak acid stress, such as that produced by sorbate or benzoate, triggers phosphorylation and possible activation of War1p (7). In turn, War1p activation allows the induction of PDR12 through a novel signal transduction event that elicits weak organic acid stress adaptation through the active efflux of weak organic acids from the cytosol (7), (1).

Last updated: 2004-07-22