Guanosine pentaphosphate

(p)ppGpp, guanosine pentaphosphate or tetraphosphate is an alarmone which is involved in the stringent response in bacteria, causing the inhibition of RNA synthesis when there is a shortage of amino acids present. This causes translation to decrease and the amino acids present are therefore conserved. Furthermore, ppGpp causes the up-regulation of many other genes involved in stress response such as the genes for amino acid uptake (from surrounding media) and biosynthesis. (p)ppGpp, guanosine pentaphosphate or tetraphosphate is an alarmone which is involved in the stringent response in bacteria, causing the inhibition of RNA synthesis when there is a shortage of amino acids present. This causes translation to decrease and the amino acids present are therefore conserved. Furthermore, ppGpp causes the up-regulation of many other genes involved in stress response such as the genes for amino acid uptake (from surrounding media) and biosynthesis. ppGpp and pppGpp were first identified by Michael Cashel in the 1960s. These nucleotides were found to accumulate rapidly in Escherichia coli cells starved for amino acids, and inhibit synthesis of ribosomal and transfer RNAs. It is now known that (p)ppGpp is also produced in response to other stressors, including carbon and phosphate starvation.