Regulation of expression of the cloned repE gene from the F plasmid of Escherichia coli.

The repE gene of the Escherichia coli F plasmid has been fused to an N-terminal fragment of the Salmonella typhimurium araB gene in the plasmid expression vector pING1. A fusion protein is expressed at high levels upon addition of arabinose to E. coli hosts containing the recombinant plasmid and has been purified to homogeneity. Antibodies prepared against the fusion protein react with both araB' and repE-coded proteins and can be used to detect their synthesis by immunoblotting methods. In vitro as well as in vivo expression of the repE gene from chimeric plasmids indicate a very tight control of the expression of this replication initiator protein.