PRODUCTION OF A PHOSPHORYLATED GST--HPV-6 E7 FUSION PROTEIN USING A YEAST EXPRESSION VECTOR AND GLUTATHIONE-S-TRANSFERASE FUSIONS

A Saccharomyces cerevisiae GAL7 expression vector for the production o f protein fusions to glutathione S-transferase (GST) has been construc ted. Using this vector, a GST fusion to human papillomavirus type 6 (H PV-6) E7 protein was produced and purified by affinity chromatography in a single step, at a yield of 2 mu g/ml of culture. The E7 portion o f the fusion protein was phosphorylated, in contrast to the same produ ct made in Escherichia coli. Therefore, yeast GST vectors may be of sp ecific use in producing phosphoproteins, or proteins with other eukary otic post-translational modifications, in preparative amounts for in v itro analysis.