Identification of a gene for a polyamine transport protein in yeast.

Abstract Properties of a membrane protein encoded byYLL028w were examined using yeast cells transformed with the gene. The transformed cells became resistant to polyamine toxicity, and the resistance was overcome by bafilomycin A1, an inhibitor of vacuolar H+-ATPase. Although spermine uptake activity of the transformed cells was almost the same as that of wild type cells, the uptake activity of vacuolar membrane vesicles from the transformed cells was higher than that from wild type cells. The transformed cells became resistant to MGBG (methylglyoxal bis(guanylhydrazone)) and paraquat, but not Ni2+ and Co2+, suggesting that the protein encoded byYLL028w is a transport protein specific for polyamines. When the YLL028w gene was disrupted by inserting theHIS3 gene, the cells became sensitive to polyamines, and spermine uptake activity of the vacuolar membrane vesicles decreased significantly. The accumulated spermine in YLL028wgene-disrupted cells decreased greatly compared with that in wild type cells. The results indicate that a membrane protein encoded byYLL028w (TPO1) is a polyamine transport protein on the vacuolar membrane.