Stimulation by ATP of protein initiation in a prokaryotic organism, B. stearothermophilus.

In contrast to E. coli ribosomes, with B. stearothermophilus ribosomes initiation complex formation is stimulated by ATP as well as GTP, but maximum stimulation occurs when both the nucleotides are present; and their terminal phosphate must be hydrolysable. In the presence of ATP and GTP, B. stearothermophilus ribosomes synthesize a highly phosphorylated guanine derivative, ppGpp, and the role of ATP in initiation might be related to this synthesis. We discarded the role of ATP as being trivial and corresponding solely to the well-known effect on eukaryotic systems.