SgrS (sugar transport-related sRNA, previously named ryaA)[1] is a 227 nucleotide small RNA that is activated by SgrR in Escherichia coli during glucose-phosphate stress. The nature of glucose-phosphate stress is not fully understood, but is correlated with intracellular accumulation of glucose-6-phosphate.[2] SgrS helps cells recover from glucose-phosphate stress by base pairing with ptsGmRNA (encoding the glucose transporter) and causing its degradation in an RNase E dependent manner.[3][4] Base pairing between SgrS and ptsGmRNA also requires Hfq, an RNA chaperone frequently required by small RNAs that affect their targets through base pairing.[5] The inability of cells expressing sgrS to create new glucose transporters leads to less glucose uptake and reduced levels of glucose-6-phosphate. SgrS is an unusual small RNA in that it also encodes a 43 amino acid functional polypeptide, SgrT, which helps cells recover from glucose-phosphate stress by preventing glucose uptake. The activity of SgrT does not affect the levels of ptsG mRNA of PtsG protein.[2] It has been proposed that SgrT exerts its effects through regulation of the glucose transporter, PtsG.[6][7]
SgrS was originally discovered in E. coli but homologues have since been identified in other Gammaproteobacteria such as Salmonella enterica and members of the genus Citrobacter.[8] A comparative genomics based target prediction approach that employs these homologs, has been developed and was used to predict the SgrS target, ptsI (b2416), which was subsequently verified experimentally.[9]
^Maki K, Morita T, Otaka H, Aiba H (May 2010). "A minimal base-pairing region of a bacterial small RNA SgrS required for translational repression of ptsG mRNA". Molecular Microbiology. 76 (3): 782–92. doi:10.1111/j.1365-2958.2010.07141.x. PMID20345651. S2CID39687800.
Vanderpool CK (April 2007). "Physiological consequences of small RNA-mediated regulation of glucose-phosphate stress". Current Opinion in Microbiology. 10 (2): 146–51. doi:10.1016/j.mib.2007.03.011. PMID17383224.
Aiba H (April 2007). "Mechanism of RNA silencing by Hfq-binding small RNAs". Current Opinion in Microbiology. 10 (2): 134–9. doi:10.1016/j.mib.2007.03.010. PMID17383928.