Tightly controlled expression systems for the production and purification of Escherichia coli release factor 1

The genes for the protein release factors in Escherichia coli have traditionally proven difficult to maintain on high copy plasmids. We have established here systems which provide for both stable maintenance of the release factor 1 gene on such plasmids, as well as high level overproduction of the release factor 1 protein. The gene is maintained under the control of the inducible trc or tac promoters in the presence of very high levels of lac repressor. A simple and rapid scheme for the purification of RF1 from extracts of cultures carrying these plasmids is also described.