SAH riboswitches are a kind of riboswitch that bind S-adenosylhomocysteine (SAH). When the coenzyme

S-adenosylmethionine ''S''-Adenosyl methionine (SAM), also known under the commercial names of SAMe, SAM-e, or AdoMet, is a common cosubstrate involved in methyl group transfers, transsulfuration, and aminopropylation. Although these anabolic reactions occur throug ...

(SAM) is used in a

methylation In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These t ...

reaction, SAH is produced. SAH riboswitches typically up-regulate genes involved in recycling SAH to create more SAM (or the metabolically related

methionine Methionine (symbol Met or M) () is an essential amino acid in humans. As the precursor of other amino acids such as cysteine and taurine, versatile compounds such as SAM-e, and the important antioxidant glutathione, methionine plays a critical ro ...

). This is particularly relevant to cells, because high levels of SAH can be toxic. Originally identified by bioinformatics, SAH riboswitches are apparent in many species of

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

, predominantly certain

Pseudomonadota Pseudomonadota (synonym Proteobacteria) is a major phylum of Gram-negative bacteria. The renaming of phyla in 2021 remains controversial among microbiologists, many of whom continue to use the earlier names of long standing in the literature. The ...

and Actinomycetota. The atomic-resolution 3-dimensional structure of an SAH riboswitch has been solved using X-ray crystallography. SAH-riboswitch

References

External links

* Cis-regulatory RNA elements Riboswitch {{molecular-cell-biology-stub