Cloning of the replication gene O of E. coli bacteriophage lambda and its expression under the control of the lac promoter.

The expression of the replication gene O of bacteriophage lambda was put under the control of the lac promoter-operator region integrated into the pBR322 cloning vehicle. The new plasmid pKK104 was introduced into minicells and the O gene induced by isopropyl-beta-thiogalactoside (IPTG). The O protein could be identified as a major component in extracts from these cells, in association with the cell membrane fractions. The molecular weight of the O protein in SDS gels is about 33 000, and it is metabolically unstable but apparently stable upon isolation as a membrane-associated fraction.