Relationship between ppGpp levels and rates of protein and RNA synthesis in Escherichia coli.

When amino acid starvation is ended in stringent (relA+) strains of escherichia coli, the rates of RNA and protein synthesis as well as their accumulation return to normal more slowly in spoT- PSTRAIns than in the spoT+ strains. The level of ppGpp accumulated declines more slowly in the spoT- strains than in the spoT+ strains. Thus, there is an inverse relationship between ppGpp levels and the rates of RNA and protein synthesis. The slow resumption of protein synthesis in the spoT- relA+ strains could therefore be explained in terms of the limited synthesis of mRNA species coding for the bulk of cellular proteins.