The stabilty and turnover of the maltose transporter of yeast: Epitope tagging of the MAL6/ gene product

The regulated uptake of wort sugars (especially maltose) by yeast is a prime determinant of beer fermentation progress. Under some nutrient-limited conditions the ability to take up sugars declines markedly so fermentation is re strained or even ceases. In order to gain a better understanding of the molecular mechanisms involved in control of maltose uptake in yeast a method for the detection and measurement of the maltose transporter in yeast cells has been developed. The maltose transporter of yeast has been tagged with a short epitope at its C terminal end by incorporating the DNA sequence encoding the epitope into the maltose transporter gene by PCR mutagenesis. Antibodies to the epitope are commercially available. It has been demonstrated that the addition of the epitope has no effect on the functional activity of the protein. The modified protein is abundantly expressed and localised to the cell membrane. The relationship between the amount of the transporter in the cell membrane and its activity under fermentation conditions is being explored. PWD acknowledge award of a BBSRC CASE studentship supported by Whitbread plc.