Unified inventory of established and putative transporters encoded within the complete genome of Saccharomyces cerevisiae

Abstract

We present the complete inventory of currently recognized and putative transporters encoded within the genome of Saccharomyces cerevisiae. These 258 transporters are classified into 42 families according to phylogenetic and substrate specificity criteria. Twelve of these yeast families are found only in eukaryotic organisms, and four are so far unique to yeast. Putative yeast-specific families transport heavy metals, arsenite and calcium. The phylogenetic analyses reported allow classification of 139 functionally uncharacterized yeast transporters into families of known functions. The relative proportions of yeast transporters specific for different classes of substrates differ only slightly from those reported for Escherichia coli. However, the ratio of secondary transporters (uniporters, cation symporters and antiporters) to primary ATP-driven transporters is much higher for yeast than for bacteria.z 1998 Federation of European Biochemical Societies.

Saccharomyces cerevisiae Multidrug Resistance Transporter Qdr2 Is Implicated in Potassium Uptake, Providing a Physiological Advantage to Quinidine-Stressed Cells

“…This can occur when growth is arrested under conditions where amino acid synthesis can continue and amino acid efflux is mediated by mechanisms that are distinct from the characterized uptake systems (13). Interestingly, the first proposed outward-pumping system for amino acid excretion was the multidrug resistance transporter of the major facilitator superfamily, Aqr1p (48), belonging to the same cluster I of the 12-spanner drug:H ϩ antiporter DHA12 family (26,30,40). However, this same role was hypothesized before for ATR1 (13,18), a member of the 14-spanner drug:H ϩ antiporter DHA14 family (26,30).…”

“…Moreover, the inspection of the genome sequences becoming available is revealing the intriguing presence of a large number of predicted multidrug transporters. In particular, this is the case for Saccharomyces cerevisiae (26,30).…”

“…QDR2 transcription, which is not stimulated in quinidine-stressed cells (47), is here demonstrated to be activated under nitrogen (NH 4 ϩ ) limitation or when the auxotrophic strain examined enters stationary phase due to leucine limitation in a Gcn4p-dependent way. Having in mind these expression results and the fact that S. cerevisiae Aqr1p, a drug:H ϩ antiporter highly homologous to Qdr2p (26,30), was proposed to be involved in the excretion of amino acids (48), we also tested the effect of QDR2 expression on amino acid partition between the cell interior and the surrounding medium. The results suggest the involvement of Qdr2p in amino acid homeostasis, directly or indirectly promoting amino acid excretion.…”

Mutants defective in secretory/vacuolar pathways in the EUROFAN collection of yeast disruptants

“…A defect was also observed in ydl115cD cells and sun4D cells, which lacked a cell wall protein involved in the final steps of septation (Mouassite et al, 2000). A slight defect was detected in cells disrupted for YNL065w, which encodes a putative drug [H + ] antiporter, with 10-12 potential transmembrane segments, belonging to the superfamily of major facilitators (Paulsen et al, 1998), and in ynl080cD cells. Cells expressing a GFP-tagged form of the latter protein, which has four potential transmembrane segments, displayed comma-shaped structures that were suggested to be Golgi stacks (Brachat et al, 2000), a hypothesis consistent with a slight defect in Golgi glycosylation.…”

Basic functional analysis of six unknown open reading frames from Saccharomyces cerevisiae: four from chromosome VII and two from chromosome XV

“…This ORF, with a length of 2178 nt, is, on the basis of sequence similarity, postulated to be a member of the oligopeptide transporter (OPT) family of membrane transporters (Paulsen et al, 1998). The disruptants are viable and show no growth defects in the routine tests carried out.…”