OVERPRODUCTION AND SINGLE-STEP PURIFICATION OF GAL4 FUSION PROTEINS FROM ESCHERICHIA-COLI

A DNA fragment encoding the yeast GAL4 transcriptional activator DNA-b inding domain (amino acids 1 93) was cloned into an Escherichia coli e xpression vector such that the overproduced protein is tagged with six histidine residues and a factor Xa protease cleavage site. The vector also contains unique restriction sites at the 3' end of the gene to a llow the construction of fusion proteins. These fusion proteins can ea sily be purified to homogeneity and their activity tested in vitro.