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.  Also, like many structured RNAs, SAM-II riboswitches can tolerate long loops between their stems.
Like other SAM riboswitches, it likely serves to suppress gene expression in response to elevated SAM levels. A notable variant of SAM-II riboswitches was discovered in Pelagibacter ubique and related marine bacteria, designated as SAM-V. Additionally, like many structured RNAs, SAM-II riboswitches can accommodate extended loops between their stems.