The inventory of all ion and drug ATPases encoded by the yeast genome

The 5,885 members of the yeast proteome have been screened for amino acid sequence signatures of either P-type ATPases or ABC transporters. A total of 16 P-type ATPases have been classified into six phylogenetic families which each seem to transport a specific class of substrates. In addition, a total of 16 ABC transporters comprising two nucleotide binding folds and two membrane domains were classified in two distinct phylogenetic families. Two ABC transporters of Family I (Pdr5p and Snq2p) share overlapping promiscuity for numerous hydrophobic drugs with a member of Family II (Yor1p). In this case, substrate specificity seems to have differentiated more slowly during evolution than typical phylogenetic traits reflected by amino acid sequence similarity or predicted membrane topography.