PHYLOGENETIC CLASSIFICATION OF THE MAJOR SUPERFAMILY OF MEMBRANE-TRANSPORT FACILITATORS, AS DEDUCED FROM YEAST GENOME SEQUENCING

From the approximately 5000 open reading frames presently identified b y systematic sequencing of the yeast genome, 100 Saccharomyces cerevis iae transport proteins belonging to the major facilitator superfamily (MFS), were assigned to 17 families on the basis of extensive database searches and binary comparisons, These families include multidrug res istance proteins and transport proteins for sugars, amino acids, uraci l/allantoin, allantoate, phosphate, purine/cytosine, proteins, peptide s, potassium, sulfate, and urea, Four new families of unknown function have been identified. For the sugar and amino acid transport proteins , alignments were made and phylogenetic trees were constructed allowin g the identification of several clusters of proteins presumably exhibi ting similar transport functions.