Synthesis of pppGpp by ribosomes from an Escherichia coli spoT mutant and the metabolic relationship between pppGpp and ppGpp.

Both ribosomes and a cell-free extract (S-30) prepared from an Escherichia coli spoT mutant catalyzed the synthesis of guanosine pentaphosphate (pppGpp) and guanosine tetraphosphate (ppGpp) as efficiently as did ribosomes and S-30 from a spoT+ strain. In both cases, the level of pppGpp reached its maximum before ppGpp maximally accumulated. pppGpp added to the ribosome system was rapidly converted to ppGpp. These results indicate that the spoT+ gene product may not have a direct role in the synthesis of pppGpp and that pppGpp is a precursor of ppGpp.