Guanosine tetraphosphate and guanosine pentaphosphate ((p)ppGpp) ((p)ppGpp)

Guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp), collectively referred to as (p)ppGpp, are specialized signaling nucleotides known as alarmones that mediate the stringent response in bacteria and plant plastids [Potrykus & Cashel, 2008, PMID: 18533940]. These molecules are synthesized by RelA/SpoT homolog (RSH) enzymes in response to various environmental stressors, such as amino acid starvation, fatty acid limitation, and heat shock [Hauryliuk et al., 2015, PMID: 25839444]. Once produced, (p)ppGpp acts as a global regulator by binding to key cellular machinery, including RNA polymerase, to rapidly downregulate stable RNA synthesis and upregulate genes required for amino acid biosynthesis and stress survival [Dalebroux & Swanson, 2012, PMID: 22542461]. In the context of human health, (p)ppGpp is a critical determinant of bacterial virulence, biofilm formation, and the development of antibiotic persistence, making it an attractive target for novel antimicrobial therapies [Wexselblatt et al., 2012, PMID: 23033245]. Current drug discovery efforts focus on small-molecule inhibitors of (p)ppGpp synthetases or synthetic analogs that competitively inhibit (p)ppGpp binding to its effector proteins [Kudrin et al., 2017, PMID: 28431245]. This signaling system is largely absent in humans, providing a high degree of selectivity for targeting bacterial pathogens without affecting host cell metabolism [Gaca et al., 2015, PMID: 26355031].

Other names

ppGpppppGppAlarmoneMagic spotGuanosine 5'-diphosphate 3'-diphosphateGuanosine 5'-triphosphate 3'-diphosphate

Competitive inhibition of (p)ppGpp binding sites on effector proteins or inhibition of (p)ppGpp biosynthetic enzymes (RelA/SpoT)