Presentor: André Goffeau, Professor

Time: 10:00am, May 27，2009

Place: A102, IMCAS

Host/Hostess: Prof. Lixin Zhang

Abstract:The Saccharomyces cerevisiae genome contains 16 genes encoding full size ABC transporters. Each comprises two cytoplasmic nucleotide binding folds (NBD) alternating with transmembrane domains (TM). We have studied in detail three plasma membrane multidrug exporters Pdr5p,Snq2p and Yor1p. The Pdr5p and Snq2p efflux transporters belong to the novel PDR subfamily which is specific to plant and fungi and shares the NBD-TM-NBD-TM topology. The Yor1p belongs to the MRP subfamily which exhibits the reciprocal TM-NBD-TM-NBD topology. The transcription of all three transporters is driven by the Zn2Cys6 transcription factors Pd1p and Pdr3p. The transporters Pdr5p, Snq2p and Yor1p show differential but overlapping substrate specificities, as shown by screening the growth inhibition caused by 349 toxic compounds on combinatorial deletants. Multiple deletion of 7 ABC genes (YOR1, SNQ2, PDR5, YCF1, PDR10, PDR11 and PDR15) and of two transcription activation factors (PDR1 and PDR3) renders the yeast cell between 2 and 200 times more sensitive to numerous toxic compounds, including most antifungals used in agriculture or medicine. Such hyper-sensitive strains allow the screening for antifungals that may not be detected in conventional pharmaceutical screens. The use of the Pdr1-3 activating mutation and the PDR5 promoter in appropriate multi-deleted hosts allows high levels of expression of Pdr5p, Snq2p or Yor1p and of heterologous Pdrp from other fungi such as from plant and human fungal pathogens These overexpressed orthologs from Candida albicans exhibit considerable multiple drug resistance in vivo. These strains can be used to screen for specific inhibitors of fungal called chemiosensitizers. The overexpressed proteins Pdr5p,Snq2p and Yor1p were purified and their ATPase and UTPase activity were characterized in vitro. Reconstituted Pdr5p was shown to be dimeric and exhibits characteristic NBD interaction in which each NBD is oriented at a 90 degree angle to each other; A thorough analysis of 365 Pdrp from over 65 fungal species shows nine different phylogenetic clusters which were classified as sensu stricto and sensu lato Pdrp！