The Control of Ribonucleic Acid Synthesis in Escherichia coli: II. STRINGENT CONTROL OF ENERGY METABOLISM

Abstract

Abstract The effect of amino acid starvation on phosphate metabolism was examined in an isogenic relaxed and stringent pair of Escherichia coli strains. The entry of Pi into the intracellular pool of orthophosphate was only slightly affected by amino acid starvation while its incorporation into the four ribonucleoside triphosphates, glucose 6-phosphate, and glucose 1-phosphate was found to be subject to stringent control. Incorporation of 32Pi into glucose-6-P continued when RNA synthesis was inhibited by actinomycin D. Thus, the entry of Pi into glucose-6-P is not governed by the rate of RNA accumulation; therefore stringent control must regulate phosphate metabolism more directly. When crude, undialyzed extracts were prepared from amino acid-starved cultures, the endogenous capacity to form glucose-6-P was found to be reduced by the stringent response, and this deficiency could be overcome by addition of an exogenous supply of ATP. These results indicate a general role of the stringent control mechanism in energy metabolism. Presumably stringency of energy metabolism and RNA accumulation share a common mechanism.