SAH riboswitch

SAH riboswitches are a kind of riboswitch that bind S-adenosylhomocysteine (SAH) [cite journal |author=Wang JX, Lee ER, Morales DR, Lim J, Breaker RR |title=Riboswitches that Sense S-adenosylhomocysteine and Activate Genes Involved in Coenzyme Recycling |journal=Mol. Cell |volume=29 |issue=6 |pages=691–702 |year=2008 |pmid=18374645 |doi=10.1016/j.molcel.2008.01.012] . 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 [cite journal |author=Ueland PM |title=Pharmacological and biochemical aspects of S-adenosylhomocysteine and S-adenosylhomocysteine hydrolase |journal=Pharmacol. Rev. |volume=34 |issue=3 |pages=223–53 |year=1982 |pmid=6760211 |doi=] . Originally identified by bioinformatics [cite journal |author=Weinberg Z, Barrick JE, Yao Z, "et al" |title=Identification of 22 candidate structured RNAs in bacteria using the CMfinder comparative genomics pipeline |journal=Nucleic Acids Res. |volume=35 |issue=14 |pages=4809–19 |year=2007 |pmid=17621584 |doi=10.1093/nar/gkm487] , SAH riboswitches are apparent in many species of bacteria, predominantly certain Proteobacteria and Actinobacteria.

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