Figure 5.

Model for RelA action during the stringent response. (A and B) Under optimal conditions, aminoacyl-tRNAs (aa-tRNAs) are delivered by EF-Tu (orange) to the A-site of the ribosome (green pathway). (C–G) Under starvation conditions (yellow pathway), the interaction of RelA (red) with deacylated A/R-tRNA at the A-site of the ribosome leads to the conversion of RelA from a ‘closed’ to an ‘open’ conformation and thereby stimulating high levels of (p)ppGpp synthesis. For more details, please refer to the text.