SAH riboswitch

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Consensus secondary structure of SAH riboswitches. Layout is similar to that used in a published depiction.[1] Three base pairs in this secondary structure were incorrectly predicted, while an additional base pair is missing, as revealed by an atomic-resolution tertiary structure.[2]
S-adenosyl-L-homocysteine riboswitch
SAH riboswitch secondary structure.jpg
Predicted secondary structure and sequence conservation of SAH_riboswitch
Symbol SAH_riboswitch
Rfam RF01057
Other data
RNA type Cis-reg; riboswitch
Domain(s) Bacteria
SO 0005836

SAH riboswitches are a kind of riboswitch that bind S-adenosylhomocysteine (SAH).[1] When the coenzyme S-adenosylmethionine (SAM) is used in a methylation reaction, SAH is produced. SAH riboswitches typically up-regulate genes involved in recycling SAH to create more SAM (or the metabolically related methionine). This is particularly relevant to cells, because high levels of SAH can be toxic.[3] Originally identified by bioinformatics,[4] SAH riboswitches are apparent in many species of bacteria, predominantly certain Proteobacteria and Actinobacteria. The atomic-resolution 3-dimensional structure of an SAH riboswitch has been solved using X-ray crystallography.[2]


  1. ^ a b Wang JX, Lee ER, Morales DR, Lim J, Breaker RR (2008). "Riboswitches that Sense S-adenosylhomocysteine and Activate Genes Involved in Coenzyme Recycling". Mol. Cell. 29 (6): 691–702. PMC 2712820Freely accessible. PMID 18374645. doi:10.1016/j.molcel.2008.01.012. 
  2. ^ a b Edwards AL, Reyes FE, Héroux A, Batey RT (September 2010). "Structural basis for recognition of S-adenosylhomocysteine by riboswitches". RNA. 16 (11): 2144–2155. PMC 2957054Freely accessible. PMID 20864509. doi:10.1261/rna.2341610. 
  3. ^ Ueland PM (1982). "Pharmacological and biochemical aspects of S-adenosylhomocysteine and S-adenosylhomocysteine hydrolase". Pharmacol. Rev. 34 (3): 223–53. PMID 6760211. 
  4. ^ Weinberg Z, Barrick JE, Yao Z, et al. (2007). "Identification of 22 candidate structured RNAs in bacteria using the CMfinder comparative genomics pipeline". Nucleic Acids Res. 35 (14): 4809–19. PMC 1950547Freely accessible. PMID 17621584. doi:10.1093/nar/gkm487. 

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