SgrS (sugar transport-related sRNA, previously named ryaA) is a 227 nucleotide small
RNA
Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
that is activated by SgrR in ''
Escherichia coli
''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escher ...
'' during
glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...
-phosphate stress. The nature of glucose-phosphate stress is not fully understood, but is correlated with intracellular accumulation of
glucose-6-phosphate
Glucose 6-phosphate (G6P, sometimes called the Robison ester) is a glucose sugar phosphorylated at the hydroxy group on carbon 6. This dianion is very common in cells as the majority of glucose entering a cell will become phosphorylated in this wa ...
.
SgrS helps cells recover from glucose-phosphate stress by base pairing with ''ptsG''
mRNA
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein.
mRNA is ...
(encoding the glucose transporter) and causing its degradation in an RNase E dependent manner.
Base pairing between SgrS and ''ptsG''
mRNA
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein.
mRNA is ...
also requires
Hfq, an RNA chaperone frequently required by small RNAs that affect their targets through base pairing. The inability of cells expressing ''sgrS'' to create new glucose transporters leads to less glucose uptake and reduced levels of
glucose-6-phosphate
Glucose 6-phosphate (G6P, sometimes called the Robison ester) is a glucose sugar phosphorylated at the hydroxy group on carbon 6. This dianion is very common in cells as the majority of glucose entering a cell will become phosphorylated in this wa ...
. SgrS is an unusual small RNA in that it also encodes a 43
amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...
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.
It has been proposed that SgrT exerts its effects through regulation of the glucose transporter, PtsG.
SgrS was originally discovered in ''E. coli'' but
homologues have since been identified in other
Gammaproteobacteria
Gammaproteobacteria is a class of bacteria in the phylum Pseudomonadota (synonym Proteobacteria). It contains about 250 genera, which makes it the most genera-rich taxon of the Prokaryotes. Several medically, ecologically, and scientifically imp ...
such as ''
Salmonella enterica
''Salmonella enterica'' (formerly ''Salmonella choleraesuis'') is a rod-headed, flagellate, facultative anaerobic, Gram-negative bacterium and a species of the genus ''Salmonella''. A number of its serovars are serious human pathogens.
Epidemi ...
'' and members of the genus ''
Citrobacter
''Citrobacter'' is a genus of Gram-negative coliform bacteria in the family Enterobacteriaceae.
The species ''C. amalonaticus'', ''C. koseri'', and ''C. freundii'' can use citrate as a sole carbon source. ''Citrobacter'' species are differentia ...
''.
A
comparative genomics
Comparative genomics is a field of biological research in which the genomic features of different organisms are compared. The genomic features may include the DNA sequence, genes, gene order, regulatory sequences, and other genomic structural lan ...
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.
References
Further reading
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External links
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sRNAmap page for SgrS RNAVanderpool Lab
Non-coding RNA
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