Patent ID: 6080542
Filing Date: 2000-06-27
Classification: C07K,C12N

Abstract:
A method for identifying a polynucleotide sequence that encodes a plant peptide transport protein which comprises introducing a competent yeast/E.coli expression vector which comprises a candidate polynucleotide into a peptide transport-deficient Saccharomyces cerevisiae strain, Saccharomyces cerevisiae strain being, further deficient in an ability to synthesize the amino acids Leu, His, and Lys; culturing said strain in a synthetic complete medium supplemented with Leu, Lys, and His; selecting at least one Saccharomyces cerevisiae transformant capable of growing on said synthetic complete medium; culturing said transformants in a minimal medium supplemented with dipeptides or tripeptides, said dipeptides or tripeptides comprising the amino acid Leu, His and Lys; selecting at least one clone which is capable of growing on said supplemented minimal medium, thereby obtaining clones which have acquired a candidate polynucleotide sequence which encodes a peptide transport protein providing said clones with the ability to transport dipeptides and tripeptides; isolating said polynucleotide sequence, and deducing the nucleotide sequence therefrom.