Fusion of the lac genes to the promoter for the aminopeptidase N gene of Escherichia coli.

Strains of Escherichia coli K12 were isolated in which the lac structural genes were fused to the promoter for the aminopeptidasee N structural gene (pepN). Although this enzyme is constitutively produced, the differential rate of synthesis is increased about 4-fold upon phosphate starvation. The pepN-lac fusions were shown to respond to phosphate specific regulatory signals. A plaque forming lambda transducing phage bearing the pepN-lac fusion was isolated. This phage was used to prove genetically the fusion of lac genes to the promoter for the aminopeptidase. These results demonstrate a control at the transcriptional level of aminopeptidase synthesis.