Stringent response
The stringent response, also called stringent control, is a stress response of bacteria and plant
(p)ppGpp
, and modulates transcription of up to 1/3 of all genes in the cell. This in turn causes the cell to divert resources away from growth and division and toward amino acid synthesis in order to promote survival until nutrient conditions improve.
Response
 | This article may be too technical for most readers to understand. (March 2020) |
In ). GDP is converted to GTP by the ndk gene product. Nucleoside triphosphate (NTP) provides the Pi, and is converted to Nucleoside diphosphate (NDP).
In other bacteria, the stringent response is mediated by a variety of RelA/SpoT Homologue (RSH) proteins,[5] with some having only synthetic, or hydrolytic or both (Rel) activities.[6]
During the stringent response, (p)ppGpp accumulation affects the resource-consuming cell processes
tRNA), and increasing the transcription of biosynthetic genes.[7] Additionally, the initiation of new rounds of replication is inhibited and the cell cycle arrests until nutrient conditions improve.[8] Translational GTPases involved in protein biosynthesis are also affected by ppGpp, with Initiation Factor 2 (IF2) being the main target.[9]
Chemical reaction catalyzed by RelA:
ATP + GTP → AMP + pppGpp
Chemical reaction catalyzed by SpoT:
ppGpp → GDP + PPi or pppGpp -> GTP + PPi