Gene expression of an Escherichia coli ribosomal RNA promoter fused to structural genes of the galactose operon.

The promoter region of the rrnB ribosomal RNA gene of Escherichia coli has been ligated within the epimerase gene (galE) of the galactose operon in a lambda phage vector. The recombinant lambda phage has been characterized by restriction mapping and assays of both galK (galactokinase) gene activity and galactose messenger RNA hybridization. In such lyosgens, expression of the fused galactose operon occurs as a function of growth rate in a manner characteristic of ribosomal RNA gene expression and is subject to stringent control by amino acid availability for protein synthesis. Galactose messenger RNA arising from the ribosomal promoter is not as metabolically stable as ribosomal RNA.