Stringent response
3991708
149745185
2007-08-07T10:37:42Z
Graeme Bartlett
38427
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The '''stringent response''' occurs in all prokaryotes and some plants in reaction to amino-acid starvation or carbon starvation. The stringent response is capable of modulating up to 1/3 of all genes in a cell. It causes the cell to divert resources away from growth and division and toward amino acid synthesis.
[[(p)ppGpp]] production is mediated by the ribosome parts: [[RelA]] and [[L11A]] when there are no charged tRNA's available to bind to the ribosome. RelA converts [[Guanosine triphosphate|GTP]] and [[Adenosine triphosphate|ATP]] into [[pppGpp]] by adding the pyrophosphate from ATP onto the 3' carbon of the ribose in GTP releasing [[Adenosine monophosphate|AMP]].
pppGpp is converted to [[ppGpp]] by the ''[[gpp]]'' gene product, releasing [[phosphate|Pi]].
ppGpp is converted to [[Guanosine diphosphate|GDP]] by the [[spoT]] gene product, releasing pyrophosphate ([[pyrophosphate|PPi]]).
GDP is converted to GTP by the ndk gene product. [[Nucleoside triphosphate|NTP]] provides the Pi, and is converted to [[Nucleoside diphosphate|NDP]].
The cycle repeats when GTP is reacted with ATP by the RelA gene.
(p)ppGpp inhibits other energy-consuming cell process, such as replication and transcription.
[[Chemical Reaction]]:
ATP ----> [[Adenosine monophosphate|AMP]]
GTP ----> pppGpp
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