Identification and characterization of Candida utilis multidrug efflux transporter CuCdr1p

The edible, nitrate assimilating, yeast Candida utilis is a commercial food additive, and it is a potentially useful host for heterologous protein expression. A number of ATP-binding cassette (ABC) transporters are multidrug efflux pumps that can cause multidrug resistance in opportunistic pathogens. In order to develop optimal novel antimicrobial agents it is imperative to understand the structure, function and expression of these transporters. With the ultimate aim of developing an alternative yeast host for the heterologous expression of eukaryotic membrane transporters, and to identify ABC transporters potentially associated with C. utilis multidrug resistance, we classified the entire repertoire of 30 C. utilis ABC proteins. We named the open reading frame most similar to the archetype multidrug efflux pump gene C. albicans CDR1 as CuCDR1 Overexpression of CuCDR1 in Saccharomyces cerevisiae ADΔ caused multidrug resistance similar to that of cells overexpressing CaCDR1 Unlike CaCdr1p, however, the C-terminally green fluorescent protein (GFP) tagged CuCdr1p-GFP was functionally impaired and did not properly localize to the plasma membrane. CuCdr1p function could be recovered however by adding a 15 amino acid linker -GAGGSAGGSGGAGAG- between CuCdr1p and the C-terminal GFP tag.