Abstract
This chapter discusses the purification of glutathione s-transferase fusion proteins from yeast. The purification of affinity-tagged recombinant proteins from prokaryotic hosts is an efficient method to obtain milligram quantities of protein for binding and activity studies. Yeast provides an opportunity to express large amounts of recombinant protein in a eukaryotic host using microbiological media. However, difficulties with the expression level of recombinant protein, toxicity of the recombinant protein, proteases, and yield from the affinity purification step have prevented researchers from taking advantage of yeast as an expression host. The choice of an appropriate host strain, induction media, and expression plasmid can overcome the expression level and protease problems, and the use of an ion-exchange resin before the affinity purification step increases recombinant protein yield, presumably by removing an inhibitor of binding to the affinity resin. The yield from these preparations is approximately 10 percent of the expressed protein; most of the loss is at the affinity purification step.