SAM-II riboswitch
The SAM-II riboswitch is an RNA element found predominantly in Alphaproteobacteria that binds S-adenosyl methionine (SAM).[1] Its structure and sequence appear to be unrelated to the SAM riboswitch found in Gram-positive bacteria. This SAM riboswitch is located upstream of the metA and metC genes in Agrobacterium tumefaciens, and other methionine and SAM biosynthesis genes in other alpha-proteobacteria. Like the other SAM riboswitch, it probably functions to turn off expression of these genes in response to elevated SAM levels. A significant variant of SAM-II riboswitches was found in Pelagibacter ubique and related marine bacteria and called SAM-V.[2] Also, like many structured RNAs, SAM-II riboswitches can tolerate long loops between their stems.[3]
Structure
The SAM-II riboswitch is short with less than 70 nucleotides and is structurally relatively simple being composed of a single hairpin and a pseudoknot.
See also
References
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