SAM-II riboswitch

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SAM riboswitch (alpha-proteobacteria)
Predicted secondary structure and sequence conservation of SAM_alpha
Symbol SAM_alpha
Rfam RF00521
Other data
RNA type Cis-reg; riboswitch
Domain(s) Bacteria
GO 0045814
SO 0000035

The SAM-II riboswitch is a RNA element found predominantly in alpha-proteobacteria 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]


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.

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