Search for the human homolog of S. cerevisiae PTR2 gene

Peptide transport is an evolutionarily conserved phenomenon with functional significance in cell nutrition. An attempt to identify a human homolog of the S. cerevisiae peptide transport gene (PTR2) was made in order to study the molecular features of the putative human gene. S. cerevisiae ptr2 mutant PB1X-9B was transformed with a HeLa cell cDNA library and ptr2⁺ transformants were selected directly on dipeptide medium. A single clone with a 10kb insert was obtained. Subsequently, the complementing region was subcloned as a 6kb fragment of the insert. Southern and DNA sequence analyses showed that the isolated clone was identical to the S. cerevisiae PTR2 and not derived from HeLa cell DNA. The explanation for this result is not apparent.