Regulatory state of ribosomal genes and physiological changes in the concentration of free ribonucleic acid polymerase in Escherichia coli

Abstract

The concept of promoter efficiency is introduced as frequency of RNA chain initiation at a given promoter normalized to the intracellular concentration of free (but functional) RNA polymerase. Previous observations from this laboratory on the synthesis of ribosomes and β-galactosidase are used to show that during a nutritional shift-up from succinate minimal to glucose-amino acids medium (3-fold increase in steady-state growth rate) the concentration of free (active) RNA polymerase decreases to one-quarter of the pre-shift value and the promoter efficiencies of the genes for ribosomal RNA and ribosomal proteins increase 9- and 6-fold respectively. This extent of control of ribosomal genes is much greater than expected on the basis of the increase in the rate of ribosome synthesis (3-fold).